Aerospace Sensor Component and Subsystem Investigation and Innovation-2 Component Exploration and Development (ASCSII-2 CED) Delivery Order 0003: Hermetically Sealed Cavities in 3-D GaAs-Silicon and Silicon-Silicon Packages for Microelectromechanical System (MEMS) Devices Using Selective and Large-Scale Bonding

DTIC Science & Technology

2003-03-01

and silicon-to-silicon to produce cavities for 3-D assembly of MEMS devices has been demonstrated using SnAgCu and eutectic SnPb solders. Laser and...of GaAs-to-silicon and silicon-to-silicon to produce cavities for 3-D assembly of MEMS devices has been demonstrated using SnAgCu and euctectic...research_images/ 3.2 Solder Reflow The reflow profile for SnAgCu solder was developed on the Sikama convection/ conduction reflow oven using a continuous

Rapid Solidification of Sn-Cu-Al Alloys for High-Reliability, Lead-Free Solder: Part II. Intermetallic Coarsening Behavior of Rapidly Solidified Solders After Multiple Reflows

NASA Astrophysics Data System (ADS)

Reeve, Kathlene N.; Choquette, Stephanie M.; Anderson, Iver E.; Handwerker, Carol A.

2016-12-01

Controlling the size, dispersion, and stability of intermetallic compounds in lead-free solder alloys is vital to creating reliable solder joints regardless of how many times the solder joints are melted and resolidified (reflowed) during circuit board assembly. In this article, the coarsening behavior of Cu x Al y and Cu6Sn5 in two Sn-Cu-Al alloys, a Sn-2.59Cu-0.43Al at. pct alloy produced via drip atomization and a Sn-5.39Cu-1.69Al at. pct alloy produced via melt spinning at a 5-m/s wheel speed, was characterized after multiple (1-5) reflow cycles via differential scanning calorimetry between the temperatures of 293 K and 523 K (20 °C and 250 °C). Little-to-no coarsening of the Cu x Al y particles was observed for either composition; however, clustering of Cu x Al y particles was observed. For Cu6Sn5 particle growth, a bimodal size distribution was observed for the drip atomized alloy, with large, faceted growth of Cu6Sn5 observed, while in the melt spun alloy, Cu6Sn5 particles displayed no significant increase in the average particle size, with irregularly shaped, nonfaceted Cu6Sn5 particles observed after reflow, which is consistent with shapes observed in the as-solidified alloys. The link between original alloy composition, reflow undercooling, and subsequent intermetallic coarsening behavior was discussed by using calculated solidification paths. The reflowed microstructures suggested that the heteroepitaxial relationship previously observed between the Cu x Al y and the Cu6Sn5 was maintained for both alloys.

Rapid Solidification of Sn-Cu-Al Alloys for High-Reliability, Lead-Free Solder: Part II. Intermetallic Coarsening Behavior of Rapidly Solidified Solders After Multiple Reflows

DOE PAGES

Reeve, Kathlene N.; Choquette, Stephanie M.; Anderson, Iver E.; ...

2016-10-06

Controlling the size, dispersion, and stability of intermetallic compounds in lead-free solder alloys is vital to creating reliable solder joints regardless of how many times the solder joints are melted and resolidified (reflowed) during circuit board assembly. In this article, the coarsening behavior of Cu x Al y and Cu 6Sn 5 in two Sn-Cu-Al alloys, a Sn-2.59Cu-0.43Al at. pct alloy produced via drip atomization and a Sn-5.39Cu-1.69Al at. pct alloy produced via melt spinning at a 5-m/s wheel speed, was characterized after multiple (1-5) reflow cycles via differential scanning calorimetry between the temperatures of 293 K and 523 Kmore » (20 °C and 250 °C). Little-to-no coarsening of the Cu x Al y particles was observed for either composition; however, clustering of Cu x Al y particles was observed. For Cu 6Sn 5 particle growth, a bimodal size distribution was observed for the drip atomized alloy, with large, faceted growth of Cu 6Sn 5 observed, while in the melt spun alloy, Cu 6Sn 5 particles displayed no significant increase in the average particle size, with irregularly shaped, nonfaceted Cu 6Sn 5 particles observed after reflow, which is consistent with shapes observed in the as-solidified alloys. The link between original alloy composition, reflow undercooling, and subsequent intermetallic coarsening behavior was discussed by using calculated solidification paths. As a result, the reflowed microstructures suggested that the heteroepitaxial relationship previously observed between the Cu x Al y and the Cu 6Sn 5 was maintained for both alloys.« less

The Melting Characteristics and Interfacial Reactions of Sn-ball/Sn-3.0Ag-0.5Cu-paste/Cu Joints During Reflow Soldering

NASA Astrophysics Data System (ADS)

Huang, J. Q.; Zhou, M. B.; Zhang, X. P.

2017-03-01

In this work, the melting characteristics and interfacial reactions of Sn-ball/Sn-3.0Ag-0.5Cu-paste/Cu (Sn/SAC305-paste/Cu) structure joints were studied using differential scanning calorimetry, in order to gain a deeper and broader understanding of the interfacial behavior and metallurgical combination among the substrate (under-bump metallization), solder ball and solder paste in a board-level ball grid array (BGA) assembly process, which is often seen as a mixed assembly using solder balls and solder pastes. Results show that at the SAC305 melting temperature of 217°C, neither the SAC305-paste nor the Sn-ball coalesce, while an interfacial reaction occurs between the SAC305-paste and Cu. A slight increase in reflow temperature (from 217°C to 218°C) results in the coalescence of the SAC305-paste with the Sn-ball. The Sn-ball exhibits premelting behavior at reflow temperatures below its melting temperature, and the premelting direction is from the bottom to the top of the Sn-ball. Remarkably, at 227°C, which is nearly 5°C lower than the melting point of pure Sn, the Sn-ball melts completely, resulting from two eutectic reactions, i.e., the reaction between Sn and Cu and that between Sn and Ag. Furthermore, a large amount of bulk Cu6Sn5 phase forms in the solder due to the quick dissolution of Cu substrate when the reflow temperature is increased to 245°C. In addition, the growth of the interfacial Cu6Sn5 layer at the SAC305-paste/Cu interface is controlled mainly by grain boundary diffusion, while the growth of the interfacial Cu3Sn layer is controlled mainly by bulk diffusion.

Study of heating capacity of focused IR light soldering systems.

PubMed

Anguiano, C; Félix, M; Medel, A; Bravo, M; Salazar, D; Márquez, H

2013-10-07

An experimental study about four optical setups used for developing a Focused IR Light Soldering System (FILSS) for Surface Mount Technology (SMT) lead-free electronic devices specifically for Ball Grid Arrays (BGA) is presented. An analysis of irradiance and infrared thermography at BGA surface is presented, as well as heat transfer by radiation and conduction process from the surface of the BGA to the solder balls. The results of this work show that the heating provided by our proposed optical setups, measured at the BGA under soldering process, meets the high temperature and uniform thermal distribution requirements, which are defined by the reflow solder method for SMT devices.

Study of Sn and SnAgCu Solders Wetting Reaction on Ni/Pd/Au Substrates

NASA Astrophysics Data System (ADS)

Liu, C. Y.; Wei, Y. S.; Lin, E. J.; Hsu, Y. C.; Tang, Y. K.

2016-12-01

Wetting reactions of pure Sn and Sn-Ag-Cu solder balls on Au(100 Å and 1000 Å)/Pd(500 Å)/Ni substrates were investigated. The (Au, Pd)Sn4 phase formed in the initial interfacial reaction between pure Sn and Au(100 Å and 1000 Å)/Pd(500 Å)/Ni substrates. Then, the initially formed (Au, Pd)Sn4 compound layer either dissolved or spalled into the molten Sn solder with 3 s of reflowing. The exposed Ni under-layer reacted with Sn solder and formed an interfacial Ni3Sn4 compound. We did not observe spalling compound in the Sn-Ag-Cu case, either on the thin Au (100 Å) or the thick Au (1000 Å) substrates. This implies that the Cu content in the Sn-Ag-Cu solder can efficiently suppress the spalling effect and really stabilize the interfacial layer. Sn-Ag-Cu solder has a better wetting than that of the pure Sn solder, regardless of the Au thickness of the Au/Pd/Ni substrate. For both cases of pure Sn and Sn-Ag-Cu, the initial wetting (<3-s reflowing) on the thin Au (100 Å) substrate is better than that of the thick Au (1000 Å) substrate. Over 3-s reflowing, the wetting on the thicker Au layer (1000 Å) substrate becomes better than the wetting on the thinner Au layer (100 Å) substrate.

Nucleation rates of Sn in undercooled Sn-Ag-Cu flip-chip solder joints

NASA Astrophysics Data System (ADS)

Arfaei, B.; Benedict, M.; Cotts, E. J.

2013-11-01

The nucleation of Sn from the melt in commercial SnAgCu flip chip solder joints was monitored at a number of different temperatures. Nucleation rates were estimated from measurements of nucleation times for 440 solder balls after one reflow and were found to be well epitomized by the expression I = 2 × 109 exp[(-1.6 × 105)/(T × (ΔT)2)] m-3 s-1, as per classical nucleation theory. After an additional reflow, the nucleation rates of the same 440 samples were observed to increase to I = 2 × 109 exp[(-8.9 × 104)/(T × (ΔT)2)] m-3 s-1. Thus it was shown that the expressions of classical nucleation theory well characterize nucleation kinetics for this system. These changes in nucleation kinetics were correlated with continued dissolution of Al and Ni in to the SnAgCu melt. Such increases in nucleation rates meant increases in the average solidification temperatures of the solder balls after reflow. Variations in the Sn grain morphology of the solder joints were correlated with these changes in solidification temperature, with larger Sn grains (beach ball Sn grain morphology) observed at higher solidification temperatures.

Mechanical Reliability of the Epoxy Sn-58wt.%Bi Solder Joints with Different Surface Finishes Under Thermal Shock

NASA Astrophysics Data System (ADS)

Sung, Yong-Gue; Myung, Woo-Ram; Jeong, Haksan; Ko, Min-Kwan; Moon, Jeonghoon; Jung, Seung-Boo

2018-04-01

The effect of thermal shock on the mechanical reliability of epoxy Sn-58wt.%Bi composite (epoxy Sn-58wt.%Bi) solder joints was investigated with different surface-finished substrates. Sn-58wt.%Bi-based solder has been considered as a promising candidate for low-temperature solder among various lead-free solders. However, Sn-58wt.%Bi solder joints can be easily broken under impact conditions such as mechanical shock, drop tests, and bending tests because of their poor ductility. Therefore, previous researchers have tried to improve the mechanical property of Sn-58wt.%Bi solder by additional elements and mixtures of metal powder and epoxy resin. Epoxy Sn-58wt.%Bi solder paste was fabricated by mixing epoxy resin and Sn-58wt.%Bi solder powder to enhance the mechanical reliability of Sn-58wt.%Bi solder joints. The epoxy Sn-58wt.%Bi solder paste was screen-printed onto various printed circuit board surfaces finished with organic solder preservatives (OSP), electroless nickel immersion gold (ENIG), and electroless nickel electroless palladium immersion gold (ENEPIG). The test components were prepared by a reflow process at a peak temperature of 190°C. The thermal shock test was carried out under the temperature range of - 40 to 125°C to evaluate the reliability of Sn-58wt.%Bi and epoxy Sn-58wt.%Bi solder joints. The OSP-finished sample showed a relatively higher mechanical property than those of ENIG and ENEPIG after thermal shock. The average number of cycles for epoxy Sn-58wt.%Bi solder with the OSP surface finish were 6 times higher than that for Sn-58wt.%Bi solder with the same finish. The microstructures of the solder joints were investigated by scanning electron microscopy, and the composition of the intermetallic compound (IMC) layer was analyzed by using energy dispersive spectrometry. Cu6Sn5 IMC was formed by the reaction between Sn-58wt.%Bi solder and a OSP surface-finished Cu after the reflow process. Ni3Sn4 IMC and (Ni, Pd)3Sn4 IMC were formed at the solder joints between the ENIG and solder, and between ENEPIG surface finish and solders, respectively.

Mechanical Reliability of the Epoxy Sn-58wt.%Bi Solder Joints with Different Surface Finishes Under Thermal Shock

NASA Astrophysics Data System (ADS)

Sung, Yong-Gue; Myung, Woo-Ram; Jeong, Haksan; Ko, Min-Kwan; Moon, Jeonghoon; Jung, Seung-Boo

2018-07-01

The effect of thermal shock on the mechanical reliability of epoxy Sn-58wt.%Bi composite (epoxy Sn-58wt.%Bi) solder joints was investigated with different surface-finished substrates. Sn-58wt.%Bi-based solder has been considered as a promising candidate for low-temperature solder among various lead-free solders. However, Sn-58wt.%Bi solder joints can be easily broken under impact conditions such as mechanical shock, drop tests, and bending tests because of their poor ductility. Therefore, previous researchers have tried to improve the mechanical property of Sn-58wt.%Bi solder by additional elements and mixtures of metal powder and epoxy resin. Epoxy Sn-58wt.%Bi solder paste was fabricated by mixing epoxy resin and Sn-58wt.%Bi solder powder to enhance the mechanical reliability of Sn-58wt.%Bi solder joints. The epoxy Sn-58wt.%Bi solder paste was screen-printed onto various printed circuit board surfaces finished with organic solder preservatives (OSP), electroless nickel immersion gold (ENIG), and electroless nickel electroless palladium immersion gold (ENEPIG). The test components were prepared by a reflow process at a peak temperature of 190°C. The thermal shock test was carried out under the temperature range of - 40 to 125°C to evaluate the reliability of Sn-58wt.%Bi and epoxy Sn-58wt.%Bi solder joints. The OSP-finished sample showed a relatively higher mechanical property than those of ENIG and ENEPIG after thermal shock. The average number of cycles for epoxy Sn-58wt.%Bi solder with the OSP surface finish were 6 times higher than that for Sn-58wt.%Bi solder with the same finish. The microstructures of the solder joints were investigated by scanning electron microscopy, and the composition of the intermetallic compound (IMC) layer was analyzed by using energy dispersive spectrometry. Cu6Sn5 IMC was formed by the reaction between Sn-58wt.%Bi solder and a OSP surface-finished Cu after the reflow process. Ni3Sn4 IMC and (Ni, Pd)3Sn4 IMC were formed at the solder joints between the ENIG and solder, and between ENEPIG surface finish and solders, respectively.

Al and Si Alloying Effect on Solder Joint Reliability in Sn-0.5Cu for Automotive Electronics

NASA Astrophysics Data System (ADS)

Hong, Won Sik; Oh, Chulmin; Kim, Mi-Song; Lee, Young Woo; Kim, Hui Joong; Hong, Sung Jae; Moon, Jeong Tak

2016-12-01

To suppress the bonding strength degradation of solder joints in automotive electronics, we proposed a mid-temperature quaternary Pb-free Sn-0.5Cu solder alloy with minor Pd, Al, Si and Ge alloying elements. We manufactured powders and solder pastes of Sn-0.5Cu-(0.01,0.03)Al-0.005Si-(0.006-0.007)Ge alloys ( T m = 230°C), and vehicle electronic control units used for a flame-retardant-4 printed circuit board with an organic solderability preservative finish were assembled by a reflow soldering process. To investigate the degradation properties of solder joints used in engine compartments, thermal cycling tests were conducted from -40°C to 125°C (10 min dwell) for 1500 cycles. We also measured the shear strength of the solder joints in various components and observed the microstructural evolution of the solder joints. Based on these results, intermetallic compound (IMC) growth at the solder joints was suppressed by minor Pd, Al and Si additions to the Sn-0.5Cu alloy. After 1500 thermal cycles, IMC layers thicknesses for 100 parts per million (ppm) and 300 ppm Al alloy additions were 6.7 μm and 10 μm, compared to the as-reflowed bonding thicknesses of 6 μm and 7 μm, respectively. Furthermore, shear strength degradation rates for 100 ppm and 300 ppm Al(Si) alloy additions were at least 19.5%-26.2%. The cause of the improvement in thermal cycling reliability was analyzed using the (Al,Cu)-Sn, Si-Sn and Al-Sn phases dispersed around the Cu6Sn5 intermetallic at the solder matrix and bonding interfaces. From these results, we propose the possibility of a mid-temperature Sn-0.5Cu(Pd)-Al(Si)-Ge Pb-free solder for automotive engine compartment electronics.

The intermetallic formation and growth kinetics at the interface of near eutectic tin-silver-copper solder alloys and gold/nickel metallization

NASA Astrophysics Data System (ADS)

Gao, Mao

The formation of a one micron thick layer of an intermetallic compound between a solder alloy and a metallic substrate generally constitutes a good solder joint in an electronic device. However, if the compound grows too thick, and/or if multiple intermetallic compounds form, poor solder joint reliability may result. Thus significant interest has been focused on intermetallic compound phase selection and growth kinetics at such solder/metal interfaces. The present study focuses on one such specific problem, the formation and growth of intermetallic compounds at near eutectic Sn-Ag-Cu solder alloy/Ni interfaces. Sn-3.0Ag-0.5Cu solder was reflowed on Au/Ni substrates, resulting in the initial formation and growth of (CuNi)6Sn 5 at Sn-3.0Ag-0.5Cu /Ni interfaces. (NiCu)3Sn4 formed between the (CuNi)6Sn5 and the Ni substrate when the concentration of Cu in the liquid SnAgCu solder decreased to a critical value which depended upon temperature: 0.37, 0.31 and 0.3(wt.%) at reflow temperatures of 260°C, 245°C and 230°C respectively. The growth rate of (CuNi)6Sn5 was found to be consistent with extrapolations of a diffusion limited growth model formulated for lower temperature, solid state diffusion couples. The long range diffusion of Cu did not limit growth rates. The spalling of (CuNiAu)6Sn5 from (NiCu)3 Sn4 surfaces during reflow was also examined. When the Cu concentration in the solder decreased to approximately 0.28wt.%, the (Cu,Ni,Au) 6Sn5 was observed to spall. Compressive stress in (CuNiAu) 6Sn5 and weak adhesion between (CuNiAu)6Sn 5 and (NiCu)3Sn4 was found to cause this effect.

New Failure Mode of Flip-Chip Solder Joints Related to the Metallization of an Organic Substrate

NASA Astrophysics Data System (ADS)

Jang, J. W.; Yoo, S. J.; Hwang, H. I.; Yuk, S. Y.; Kim, C. K.; Kim, S. J.; Han, J. S.; An, S. H.

2015-10-01

We report a new failure phenomenon during flip-chip die attach. After reflow, flip-chip bumps were separated between the Al and Ti layers on the Si die side. This was mainly observed at the Si die corner. Transmission electron microscopy images revealed corrosion of the Al layer at the edge of the solder bump metallization. The corrosion at the metallization edge exhibited a notch shape with high stress concentration factor. The organic substrate had Cu metallization with an organic solderable preservative (OSP) coating layer, where a small amount of Cl ions were detected. A solder bump separation mechanism is suggested based on the reaction between Al and Cl, related to the flow of soldering flux. During reflow, the flux will dissolve the Cl-containing OSP layer and flow up to the Al layer on the Si die side. Then, the Cl-dissolved flux will actively react with Al, forming AlCl3. During cooling, solder bumps at the Si die corner will separate through the location of Al corrosion. This demonstrated that the chemistry of the substrate metallization can affect the thermomechanical reliability of flip-chip solder joints.

Effect of Temperature Cycling and Exposure to Extreme Temperatures on Reliability of Solid Tantalum Capacitors

NASA Technical Reports Server (NTRS)

Teverovsky, Alexander

2007-01-01

In this work, results of multiple temperature cycling (TC) (up to 1,000 cycles) of different types of solid tantalum capacitors are analyzed and reported. Deformation of chip tantalum during temperature variations simulating reflow soldering conditions was measured to evaluate the possibility of the pop-corning effect in the parts. To simulate the effect of short-time exposures to solder reflow temperatures on the reliability of tantalum capacitors, several part types were subjected to multiple cycles (up to 100) between room temperature and 240 C with periodical measurements of electrical characteristics of the parts. Mechanisms of degradation caused by temperature cycling and exposure to high temperatures, and the requirements of MIL-PRF-55365 for assessment of the resistance of the parts to soldering heat are discussed.

Intermetallic Compounds Formed in Sn-20In-2.8Ag Solder BGA Packages with Ag/Cu Pads

NASA Astrophysics Data System (ADS)

Jain, C. C.; Wang, S. S.; Huang, K. W.; Chuang, T. H.

2009-03-01

The interfacial reactions in a Sn-20In-2.8Ag solder ball grid array (BGA) package with immersion Ag surface finish are investigated. After reflow, the Ag thin film dissolves quickly into the solder matrix, and scallop-shaped intermetallic layers, with compositions of (Cu0.98Ag0.02)6(In0.59Sn0.41)5, appear at the interfaces between Sn-20In-2.8Ag solder ball and Cu pad. No evident growth of the (Cu0.98Ag0.02)6(Sn0.59In0.41)5 intermetallic compounds was observed after prolonged aging at 100 °C. However, the growth accelerated at 150 °C, with more intermetallic scallops floating into the solder matrix. The intermetallic thickness versus the square root of reaction time ( t 1/2) shows a linear relation, indicating that the growth of intermetallic compounds is diffusion-controlled. Ball shear tests show that the strength of Sn-20In-2.8Ag solder joints after reflow is 4.4 N, which increases to 5.18 N and 5.14 N after aging at 100 and 150 °C, respectively.

Solder flow over fine line PWB surface finishes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hosking, F.M.; Hernandez, C.L.

1998-08-01

The rapid advancement of interconnect technology has stimulated the development of alternative printed wiring board (PWB) surface finishes to enhance the solderability of standard copper and solder-coated surfaces. These new finishes are based on either metallic or organic chemistries. As part of an ongoing solderability study, Sandia National Laboratories has investigated the solder flow behavior of two azole-based organic solderability preservations, immersion Au, immersion Ag, electroless Pd, and electroless Pd/Ni on fine line copper features. The coated substrates were solder tested in the as-fabricated and environmentally-stressed conditions. Samples were processed through an inerted reflow machine. The azole-based coatings generally providedmore » the most effective protection after aging. Thin Pd over Cu yielded the best wetting results of the metallic coatings, with complete dissolution of the Pd overcoat and wetting of the underlying Cu by the flowing solder. Limited wetting was measured on the thicker Pd and Pd over Ni finishes, which were not completely dissolved by the molten solder. The immersion Au and Ag finishes yielded the lowest wetted lengths, respectively. These general differences in solderability were directly attributed to the type of surface finish which the solder came in contact with. The effects of circuit geometry, surface finish, stressing, and solder processing conditions are discussed.« less

Life testing of reflowed and reworked advanced CCGA surface mount packages in harsh thermal environments

NASA Astrophysics Data System (ADS)

Ramesham, Rajeshuni

2013-03-01

Life testing/qualification of reflowed (1st reflow) and reworked (1st reflow, 1st removal, and then 1st rework) advanced ceramic column grid array (CCGA) surface mount interconnect electronic packaging technologies for future flight projects has been studied to enhance the mission assurance of JPL-NASA projects. The reliability of reworked/reflowed surface mount technology (SMT) packages is very important for short-duration and long-duration deep space harsh extreme thermal environmental missions. The life testing of CCGA electronic packages under extreme thermal environments (for example: -185°C to +125°C) has been performed with reference to various JPL/NASA project requirements which encompass the temperature range studied. The test boards of reflowed and reworked CCGA packages (717 Xilinx package, 624, 1152, and 1272 column Actel Packages) were selected for the study to survive three times the total number of expected temperature cycles resulting from all environmental and operational exposures occurring over the life of the flight hardware including all relevant manufacturing, ground operations, and mission phases or cycles to failure to assess the life of the hardware. Qualification/life testing was performed by subjecting test boards to the environmental harsh temperature extremes and assessing any structural failures, mechanical failures or degradation in electrical performance solder-joint failures due to either overstress or thermal cycle fatigue. The large, high density, high input/output (I/O) electronic interconnect SMT packages such as CCGA have increased usage in avionics hardware of NASA projects during the last two decades. The test boards built with CCGA packages are expensive and often require a rework to replace a reflowed, reprogrammed, failed, redesigned, etc., CCGA packages. Theoretically speaking, a good rework process should have similar temperature-time profile as that used for the original manufacturing process of solder reflow. A multiple rework processes may be implemented with CCGA packaging technology to understand the effect of number of reworks on the reliability of this technology for harsh thermal environments. In general, reliability of the assembled electronic packages reduces as a function of number of reworks and the extent is not known yet. A CCGA rework process has been tried and implemented to design a daisy-chain test board consists of 624 and 717 packages. Reworked CCGA interconnect electronic packages of printed wiring polyimide boards have been assembled and inspected using non-destructive x-ray imaging and optical microscope techniques. The assembled boards after 1st rework and 1st reflow were subjected to extreme temperature thermal atmospheric cycling to assess their reliability for future deep space JPL/NASA for moderate to harsh thermal mission environments. The resistance of daisy-chained interconnect sections were monitored continuously during thermal cycling to determine intermittent failures. This paper provides the experimental reliability test results to failure of assemblies for the first time of reflowed and reworked CCGA packages under extreme harsh thermal environments.

Beta-Tin Grain Formation in Aluminum-Modified Lead-Free Solder Alloys

NASA Astrophysics Data System (ADS)

Reeve, Kathlene N.; Handwerker, Carol A.

2018-01-01

The limited number of independent β-Sn grain orientations that typically form during solidification of Sn-based solders and the resulting large β-Sn grain size have major effects on overall solder performance and reliability. This study analyzes whether additions of Al to Sn-Cu and Sn-Cu-Ag alloys can be used to change the grain size, morphology, and twinning structures of atomized (as-solidified) and re-melted (reflowed) β-Sn dendrites as determined using scanning electron microscopy and electron backscatter diffraction for as-solidified and reflow cycled (20-250°C, 1-5 cycles) Sn-Cu-Al and Sn-Ag-Cu-Al drip atomized spheres (260 μm diameter). The resulting microstructures were compared to as-solidified and reflow cycled Sn-Ag-Cu spheres (450 μm diameter) as well as as-solidified Sn-Ag-Cu, Sn-Cu, and Sn-Ag microstructures from the literature. Previous literature observations reporting reductions in undercooling and β-Sn grain size with Al micro-alloying additions could not be correlated to the presence of the Cu9Al4 phase or Al solute. The as-solidified spheres displayed no change in β-Sn dendrite structure or grain size when compared to non-Al-modified alloys, and the reflow cycled spheres produced high undercoolings (22-64°C), indicating a lack of potent nucleation sites. The current findings highlighted the role of Ag in the formation of the interlaced twinning structure and demonstrated that with deliberate compositional choices, formation of the alloy's β-Sn grain structure (cyclical twinning versus interlaced twinning) could be influenced, in both the as-solidified and reflow cycled states, though still not producing the fine-grain sizes and multiple orientations desired for improved thermomechanical properties.

Development of n+-in-p planar pixel quadsensor flip-chipped with FE-I4 readout ASICs

NASA Astrophysics Data System (ADS)

Unno, Y.; Kamada, S.; Yamamura, K.; Yamamoto, H.; Hanagaki, K.; Hori, R.; Ikegami, Y.; Nakamura, K.; Takubo, Y.; Takashima, R.; Tojo, J.; Kono, T.; Nagai, R.; Saito, S.; Sugibayashi, K.; Hirose, M.; Jinnouchi, O.; Sato, S.; Sawai, H.; Hara, K.; Sato, Kz.; Sato, Kj.; Iwabuchi, S.; Suzuki, J.

2017-01-01

We have developed flip-chip modules applicable to the pixel detector for the HL-LHC. New radiation-tolerant n+-in-p planar pixel sensors of a size of four FE-I4 application-specific integrated circuits (ASICs) are laid out in a 6-in wafer. Variation in readout connection for the pixels at the boundary of ASICs is implemented in the design of quadsensors. Bump bonding technology is developed for four ASICs onto one quadsensor. Both sensors and ASICs are thinned to 150 μm before bump bonding, and are held flat with vacuum chucks. Using lead-free SnAg solder bumps, we encounter deficiency with large areas of disconnected bumps after thermal stress treatment, including irradiation. Surface oxidation of the solder bumps is identified as a critical source of this deficiency after bump bonding trials, using SnAg bumps with solder flux, indium bumps, and SnAg bumps with a newly-introduced hydrogen-reflow process. With hydrogen-reflow, we establish flux-less bump bonding technology with SnAg bumps, appropriate for mass production of the flip-chip modules with thin sensors and thin ASICs.

A Study on the Effect of Ageing and Intermetallic Compound Growth on the Shear Strength of Surface Mount Technology Solder Joints

NASA Astrophysics Data System (ADS)

Nath, Jyotishman; Mallik, Sabuj; Borah, Anil

2015-04-01

The effect of ageing and intermetallic compound formation on the surface mount solder joints and its shear strength behavior under extreme mechanical and thermal conditions have been discussed in this paper. The specimens used are solder paste (Sn3.8Ag0.7Cu), bench marker II printed circuit boards (PCB), resistors 1206 and the fabrication of solder joints makes use of conventional surface mount technology (SMT). Reflow process was carried out at a peak temperature of 250 °C and the test samples were exposed to isothermal ageing at a constant temperature of 150 °C for a period of 600 h. Shear test was conducted on the PCB's. The shear strength of the solder joints rapidly increased during isothermal ageing to a certain time period and then started decreasing. Field emission scanning electron microscopy (FESEM) micrograph of the solder joint and energy dispersive X-ray (EDX) was performed on the solder sample to verify the formation of intermetallic compounds.

2005 DoD Diminishing Manufacturing Sources and Material Shortages

DTIC Science & Technology

2005-12-15

free Solder Issues Temperature stress Prevailing Pb-free solder replacement ( SnAgCu ) has ~35°C higher reflow temperature Infant mortality Latent...SnCu, SnAgCu Few microns to over 1mm Electrically conductive Crystalline Whisker induced failures: Short Circuit – bridges two adjacent pins Metal

Effects of In and Ni Addition on Microstructure of Sn-58Bi Solder Joint

NASA Astrophysics Data System (ADS)

Mokhtari, Omid; Nishikawa, Hiroshi

2014-11-01

In this study, the effect of adding 0.5 wt.% and 1 wt.% In and Ni to Sn-58Bi solder on intermetallic compound (IMC) layers at the interface and the microstructure of the solder alloys were investigated during reflow and thermal aging by scanning electron microscopy and electron probe micro-analysis. The results showed that the addition of minor elements was not effective in suppressing the IMC growth during the reflow; however, the addition of 0.5 wt.% In and Ni was effective in suppressing the IMC layer growth during thermal aging. The thickening kinetics of the total IMC layer was analyzed by plotting the mean thickness versus the aging time on log-log coordinates, and the results showed the transition point from grain boundary diffusion control to a volume diffusion control mechanism. The results also showed that the minor addition of In can significantly suppress the coarsening of the Bi phase.

Refinement of the β-Sn Grains in Ni-Doped Sn-3.0Ag-0.5Cu Solder Joints with Cu-Based and Ni-Based Substrates

NASA Astrophysics Data System (ADS)

Chou, Tzu-Ting; Chen, Wei-Yu; Fleshman, Collin Jordon; Duh, Jenq-Gong

2018-03-01

A fine-grain structure with random orientations of lead-free solder joints was successfully obtained in this study. The Sn-Ag-Cu solder alloys doped with minor Ni were reflowed with Ni-based or Cu-based substrates to fabricate the joints containing different Ni content. Adding 0.1 wt.% Ni into the solder effectively promoted the formation of fine Sn grains, and reflowing with Ni-based substrates further enhanced the effects of β-Sn grain refinement. The crystallographic characteristics and the microstructures were analyzed to identify the solidification mechanism of different types of microstructure in the joints. The phase precipitating order in the joint altered as the solder composition were modified by elemental doping and changing substrate, which significantly affected the efficiency of grain refinement and the final grain structure. The formation mechanism of fine β-Sn grains in the Ni-doped joint with a Ni-based substrate is attributable to the heterogeneous nucleation by Ni, whereas the Ni in the joint using ChouCu-based substrate is consumed to form an intermetallic compound and thus retard the effect of grain refining.

Effect of Plasma Surface Finish on Wettability and Mechanical Properties of SAC305 Solder Joints

NASA Astrophysics Data System (ADS)

Kim, Kyoung-Ho; Koike, Junichi; Yoon, Jeong-Won; Yoo, Sehoon

2016-12-01

The wetting behavior, interfacial reactions, and mechanical reliability of Sn-Ag-Cu solder on a plasma-coated printed circuit board (PCB) substrate were evaluated under multiple heat-treatments. Conventional organic solderability preservative (OSP) finished PCBs were used as a reference. The plasma process created a dense and highly cross-linked polymer coating on the Cu substrates. The plasma finished samples had higher wetting forces and shorter zero-cross times than those with OSP surface finish. The OSP sample was degraded after sequential multiple heat treatments and reflow processes, whereas the solderability of the plasma finished sample was retained after multiple heat treatments. After the soldering process, similar microstructures were observed at the interfaces of the two solder joints, where the development of intermetallic compounds was observed. From ball shear tests, it was found that the shear force for the plasma substrate was consistently higher than that for the OSP substrate. Deterioration of the OSP surface finish was observed after multiple heat treatments. Overall, the plasma surface finish was superior to the conventional OSP finish with respect to wettability and joint reliability, indicating that it is a suitable material for the fabrication of complex electronic devices.

Lead free 0201 assembly and thermal cycle/aging reliability

NASA Technical Reports Server (NTRS)

Ghaffarian, Reza; Ramkumar, S. Manian; Varanasi, Arun

2005-01-01

The many challenges with 0201 passive component assembly can be attributed to the solder paste volume, pad design, aperture design, board finish, type of solder paste, pick-and-place, and reflow profile. A Design-of-Experiment (DOE) study was carried out to investigate the effects of these parameters on assembly defects and reliability.

A Comparative Study on the Microstructure and Mechanical Properties of Cu6Sn5 and Cu3Sn Joints Formed by TLP Soldering With/Without the Assistance of Ultrasonic Waves

NASA Astrophysics Data System (ADS)

Zhao, H. Y.; Liu, J. H.; Li, Z. L.; Song, X. G.; Zhao, Y. X.; Niu, H. W.; Tian, H.; Dong, H. J.; Feng, J. C.

2018-07-01

In this study, the microstructure and mechanical properties of Cu6Sn5 and Cu3Sn intermetallic joints, formed by the transient liquid phase (TLP) soldering process with and without the assistance of ultrasonic waves (USWs), were compared. After the application of USWs in the TLP soldering process, Cu-Sn intermetallic compounds (IMCs) exhibited a novel noninterfacial growth pattern in the molten solder interlayer. The resulting Cu6Sn5 and Cu3Sn joints consisted of refined equiaxed IMC grains with average sizes of 3 and 2.3 µm, respectively. The Cu6Sn5 grains in the ultrasonically soldered intermetallic joints demonstrated uniform mechanical properties with elastic modulus and hardness values of 123.0 and 5.98 GPa, respectively, while those of Cu3Sn grains were 133.9 and 5.08 GPa, respectively. The shear strengths of ultrasonically soldered Cu6Sn5 and Cu3Sn joints were measured to be 60 and 65 MPa, respectively, higher than that for reflow-soldered intermetallic joints. Ultrasonically soldered Cu6Sn5 and Cu3Sn joints both exhibited a combination of transgranular and intergranular fractures during shear testing.

A Comparative Study on the Microstructure and Mechanical Properties of Cu6Sn5 and Cu3Sn Joints Formed by TLP Soldering With/Without the Assistance of Ultrasonic Waves

NASA Astrophysics Data System (ADS)

Zhao, H. Y.; Liu, J. H.; Li, Z. L.; Song, X. G.; Zhao, Y. X.; Niu, H. W.; Tian, H.; Dong, H. J.; Feng, J. C.

2018-05-01

In this study, the microstructure and mechanical properties of Cu6Sn5 and Cu3Sn intermetallic joints, formed by the transient liquid phase (TLP) soldering process with and without the assistance of ultrasonic waves (USWs), were compared. After the application of USWs in the TLP soldering process, Cu-Sn intermetallic compounds (IMCs) exhibited a novel noninterfacial growth pattern in the molten solder interlayer. The resulting Cu6Sn5 and Cu3Sn joints consisted of refined equiaxed IMC grains with average sizes of 3 and 2.3 µm, respectively. The Cu6Sn5 grains in the ultrasonically soldered intermetallic joints demonstrated uniform mechanical properties with elastic modulus and hardness values of 123.0 and 5.98 GPa, respectively, while those of Cu3Sn grains were 133.9 and 5.08 GPa, respectively. The shear strengths of ultrasonically soldered Cu6Sn5 and Cu3Sn joints were measured to be 60 and 65 MPa, respectively, higher than that for reflow-soldered intermetallic joints. Ultrasonically soldered Cu6Sn5 and Cu3Sn joints both exhibited a combination of transgranular and intergranular fractures during shear testing.

Survivability of soldered leadless chip carriers after temperature cycling

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zawicki, L.R.; Lenhardt, B.W.; Smith, F.R.

Temperature cycling evaluations were conducted on leadless chip carriers (LCCs) soldered to thick film networks (TKNs). Various temperature ranges, rates of change, cycle times, number of cycles, and sizes of LCCs were used. The TKNs were attached to metal backing plates with 63Sn/37Pb solder preforms using an infrared vacuum soldering process. The LCCs were attached to Pt/Au TKNs with 63Sn/37Pb solder paste using a belt reflow process. Visual examination and cross-sectional analysis were used to evaluate the survivability. Results were also correlated with finite elemental analysis. Considering the initial results, possible solutions included changing the solder from 63Sn/37Pb to 50Pb/50In,more » deleting the metal backplate, changing the rate of change in the temperature cycle, and/or adding leads to the large LCCs. Because of a system requirement, the rate of change in the temperature cycle could not be changed. Since there was no long term reliability information on the Pt/Au TKN with 50Pb/50In solder, this option was also dropped. Additional evaluations showed little difference in the survivability of large LCC solder joints with or without the metal backing plate. The final results indicated that LCCs beyond a certain physical size required compliant leads to survive the temperature cycle requirements.« less

Logistics for the implementation of lead-free solders on electronic assemblies

DOE Office of Scientific and Technical Information (OSTI.GOV)

Vianco, P.T.; Artaki, I.

1993-12-31

The prospects of legislative and regulatory action aimed at taxing, restricting or banning lead-bearing materials from manufactured products has prompted the electronics community to examine the implementation of lead-free solders to replace currently used lead-containing alloys in the manufacture of electronic devices and assemblies. The logistics for changing the well established ``tin-lead solder technology`` require not only the selection of new compositions but also the qualification of different surface finishes and manufacturing processes. The meniscometer/wetting balance technique was used to evaluate the wettability of several candidate lead-free solders as well as to establish windows on processing parameters so as tomore » facilitate prototype manufacturing. Electroplated and electroless 100Sn coatings, as well as organic preservatives, were also examined as potential alternative finishes for device leads and terminations as well as circuit board conductor surfaces to replace traditional tin-lead layers. Sandia National Laboratories and AT&T have implemented a program to qualify the manufacturing feasibility of surface mount prototype circuit boards using several commercial lead-free solders by infrared reflow technology.« less

Soldering Characteristics and Mechanical Properties of Sn-1.0Ag-0.5Cu Solder with Minor Aluminum Addition

PubMed Central

Leong, Yee Mei; Haseeb, A.S.M.A.

2016-01-01

Driven by the trends towards miniaturization in lead free electronic products, researchers are putting immense efforts to improve the properties and reliabilities of Sn based solders. Recently, much interest has been shown on low silver (Ag) content solder SAC105 (Sn-1.0Ag-0.5Cu) because of economic reasons and improvement of impact resistance as compared to SAC305 (Sn-3.0Ag-0.5Cu. The present work investigates the effect of minor aluminum (Al) addition (0.1–0.5 wt.%) to SAC105 on the interfacial structure between solder and copper substrate during reflow. The addition of minor Al promoted formation of small, equiaxed Cu-Al particle, which are identified as Cu3Al2. Cu3Al2 resided at the near surface/edges of the solder and exhibited higher hardness and modulus. Results show that the minor addition of Al does not alter the morphology of the interfacial intermetallic compounds, but they substantially suppress the growth of the interfacial Cu6Sn5 intermetallic compound (IMC) after reflow. During isothermal aging, minor alloying Al has reduced the thickness of interfacial Cu6Sn5 IMC but has no significant effect on the thickness of Cu3Sn. It is suggested that of atoms of Al exert their influence by hindering the flow of reacting species at the interface. PMID:28773645

Soldering Characteristics and Mechanical Properties of Sn-1.0Ag-0.5Cu Solder with Minor Aluminum Addition.

PubMed

Leong, Yee Mei; Haseeb, A S M A

2016-06-28

Driven by the trends towards miniaturization in lead free electronic products, researchers are putting immense efforts to improve the properties and reliabilities of Sn based solders. Recently, much interest has been shown on low silver (Ag) content solder SAC105 (Sn-1.0Ag-0.5Cu) because of economic reasons and improvement of impact resistance as compared to SAC305 (Sn-3.0Ag-0.5Cu. The present work investigates the effect of minor aluminum (Al) addition (0.1-0.5 wt.%) to SAC105 on the interfacial structure between solder and copper substrate during reflow. The addition of minor Al promoted formation of small, equiaxed Cu-Al particle, which are identified as Cu₃Al₂. Cu₃Al₂ resided at the near surface/edges of the solder and exhibited higher hardness and modulus. Results show that the minor addition of Al does not alter the morphology of the interfacial intermetallic compounds, but they substantially suppress the growth of the interfacial Cu₆Sn₅ intermetallic compound (IMC) after reflow. During isothermal aging, minor alloying Al has reduced the thickness of interfacial Cu₆Sn₅ IMC but has no significant effect on the thickness of Cu₃Sn. It is suggested that of atoms of Al exert their influence by hindering the flow of reacting species at the interface.

Maintaining Low Voiding Solder Die Attach for Power Die While Minimizing Die Tilt

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hamm, Randy; Peterson, Kenneth A.

2015-10-01

This paper addresses work to minimize voiding and die tilt in solder attachment of a large power die, measuring 9.0 mm X 6.5 mm X 0.1 mm (0.354” x 0.256” x 0.004”), to a heat spreader. As demands for larger high power die continue, minimizing voiding and die tilt is of interest for improved die functionality, yield, manufacturability, and reliability. High-power die generate considerable heat, which is important to dissipate effectively through control of voiding under high thermal load areas of the die while maintaining a consistent bondline (minimizing die tilt). Voiding was measured using acoustic imaging and die tiltmore » was measured using two different optical measurement systems. 80Au-20Sn solder reflow was achieved using a batch vacuum solder system with optimized fixturing. Minimizing die tilt proved to be the more difficult of the two product requirements to meet. Process development variables included tooling, weight and solder preform thickness.« less

Flip-chip replacement within the constraints imposed by multilayer ceramic (MLC) modules

NASA Astrophysics Data System (ADS)

Puttlitz, Karl J.

1984-01-01

Economics often dictates that suitable module rework procedures be established to replace solder bump devices (flip chips) reflowed to multichip carriers. These operations are complicated, owing to various constraints such as the substrate's physical and mechanical properties, close proximity of surface features, etc. This paper describes the constraints and the methods to circumvent them. An order of preference based upon the degree of constraint is recommended to achieve device removal and subsequent site dress of the residual solder left on the substrate. It has been determined that rework (device replacement) can be successfully achieved in even highly constricted situations. This is illustrated by the example of utilizing a localized heating technique, hot gas, to remove solder from microsockets from which chips were previously removed. Microsockets are areas to which chips are reflowed to the top surface of IBM's densely populated multilayer ceramic (MLC) modules, thus forming the so-called controlled collapse chip connection or C-4. The microsocket patterns are thus identical to the chip footprint.

Packaging of ferroelectric liquid crystal-on-silicon spatial light modulators

NASA Astrophysics Data System (ADS)

Lin, W.; Morozova, Nina D.; Ju, TehHua; Zhang, Weidong; Lee, Yung-Cheng; McKnight, Douglas J.; Johnson, Kristina M.

1996-11-01

A self-pulling soldering technology has been demonstrated for assembling liquid crystal on silicon (LCOS) spatial light modulators (SLMs). One of the major challenges in manufacturing the LCOS modules is to reproducibly control the thickness of the gap between the very large scale integrated circuit (VLSI) chip and the cover glass. The liquid crystal material is sandwiched between the VLSI chop and the cover glass which is coated with a transparent conductor. Solder joints with different profiles and sizes have been designed to provide surface tension forces to control the gap accommodating the ferroelectric liquid crystal layer in the range of a micron level with sub- micron uniformity. The optimum solder joint design is defined as a joint that results in the maximum pulling force. This technology provides an automatic, batch assembly process for a LCOS SLM through one reflow process. Fluxless soldering technology is used to assemble the module. This approach avoids residues from chemical of flux and oxides, and eliminates potential contamination to the device. Two different LCOS SLM designs and the process optimization are described.

Effects of metallic nanoparticle doped flux on the interfacial intermetallic compounds between lead-free solder ball and copper substrate

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sujan, G.K., E-mail: sgkumer@gmail.com; Haseeb, A.S.M.A., E-mail: haseeb@um.edu.my; Afifi, A.B.M., E-mail: amalina@um.edu.my

2014-11-15

Lead free solders currently in use are prone to develop thick interfacial intermetallic compound layers with rough morphology which are detrimental to the long term solder joint reliability. A novel method has been developed to control the morphology and growth of intermetallic compound layers between lead-free Sn–3.0Ag–0.5Cu solder ball and copper substrate by doping a water soluble flux with metallic nanoparticles. Four types of metallic nanoparticles (nickel, cobalt, molybdenum and titanium) were used to investigate their effects on the wetting behavior and interfacial microstructural evaluations after reflow. Nanoparticles were dispersed manually with a water soluble flux and the resulting nanoparticlemore » doped flux was placed on copper substrate. Lead-free Sn–3.0Ag–0.5Cu solder balls of diameter 0.45 mm were placed on top of the flux and were reflowed at a peak temperature of 240 °C for 45 s. Angle of contact, wetting area and interfacial microstructure were studied by optical microscopy, field emission scanning electron microscopy and energy-dispersive X-ray spectroscopy. It was observed that the angle of contact increased and wetting area decreased with the addition of cobalt, molybdenum and titanium nanoparticles to flux. On the other hand, wettability improved with the addition of nickel nanoparticles. Cross-sectional micrographs revealed that both nickel and cobalt nanoparticle doping transformed the morphology of Cu{sub 6}Sn{sub 5} from a typical scallop type to a planer one and reduced the intermetallic compound thickness under optimum condition. These effects were suggested to be related to in-situ interfacial alloying at the interface during reflow. The minimum amount of nanoparticles required to produce the planer morphology was found to be 0.1 wt.% for both nickel and cobalt. Molybdenum and titanium nanoparticles neither appear to undergo alloying during reflow nor have any influence at the solder/substrate interfacial reaction. Thus, doping of flux with appropriate metallic nanoparticles can be successfully used to control the morphology and growth of intermetallic compound layers at the solder/substrate interface which is expected to lead to better reliability of electronic devices. - Highlights: • A novel nanodoped flux method has been developed to control the growth of IMCs. • Ni doped flux improves the wettability, but Co, Mo and Ti deteriorate it. • Ni and Co doped flux gives planer IMC morphology through in-situ alloying effect. • 0.1 wt.% Ni and Co addition into flux gives the lowest interfacial IMC thickness. • Mo and Ti doped flux does not have any influence at the interfacial reaction.« less

Effect of Ni addition to the Cu substrate on the interfacial reaction and IMC growth with Sn3.0Ag0.5Cu solder

NASA Astrophysics Data System (ADS)

Zhang, Xudong; Hu, Xiaowu; Jiang, Xiongxin; Li, Yulong

2018-04-01

The formation and growth of intermetallic compound (IMC) layer at the interface between Sn3.0Ag0.5Cu (SAC305) solder and Cu- xNi ( x = 0, 0.5, 1.5, 5, 10 wt%) substrate during reflowing and aging were investigated. The soldering was conducted at 270 °C using reflowing method, following by aging treatment at 150 °C for up to 360 h. The experimental results indicated that the total thickness of IMC increased with increasing aging time. The scallop-like Cu6Sn5 and planar-like Cu3Sn IMC layer were observed between SAC305 solder and purely Cu substrate. As the content of Ni element in Cu substrate was 0.5% or 1.5%, the scallop-like Cu6Sn5 and planar-like Cu3Sn IMC layer were still found between solder and Cu-Ni substrate and the total thickness of IMC layer decreased with the increasing Ni content. Besides, when the Ni content was up to 5%, the long prismatic (Cu,Ni)6Sn5 phase was the only product between solder and substrate and the total thickness of IMC layer increased significantly. Interestingly, the total thickness of IMC decreased slightly as the Ni addition was up to 10%. In the end, the grains of interfacial IMC layer became coarser with aging time increasing while the addition of Ni in Cu substrate could refine IMC grains.

Effect of Cu concentration on morphology of Sn-Ag-Cu solders by mechanical alloying

NASA Astrophysics Data System (ADS)

Kao, Szu-Tsung; Duh, Jenq-Gong

2004-12-01

The mechanical alloying (MA) process is considered an alternative approach to produce solder materials. In this study, the effect of Cu concentration in the ternary Sn-3.5Ag-xCu (x=0.2, 0.7, and 1) solder by MA was investigated. The (Cu,Sn) solid solution was precipitated as the Cu6Sn5 intermetallic compound (IMC), which was distributed nonuniformly through the microstructure. The Cu6Sn5 IMC, which was present in the SnAgCu solder with high Cu composition, causes the as-milled MA particle to fracture to a smaller size. Appreciable distinction on morphology of as-milled MA powders with different Cu content was revealed. When the Cu concentration was low (x=0.2), MA particle aggregated to a spherical ingot with large particle size. For higher Cu concentration (x=0.7 and x=1), the MA particle turned to flakes with smaller particle size. The distinction of the milling mechanism of Sn-3.5Ag-xCu (x=0.2, 0.7, and 1) solder by the MA process was discussed. An effective approach was developed to reduce the particle size of the SnAgCu solder from 1 mm down to 10-100 µm by doping the Cu6Sn5 nanoparticle during the MA process. In addition, the differential scanning calorimetry (DSC) results also ensure the compatibility to apply the solder material for the reflow process.

Optimization of Indium Bump Morphology for Improved Flip Chip Devices

NASA Technical Reports Server (NTRS)

Jones, Todd J.; Nikzad, Shouleh; Cunningham, Thomas J.; Blazejewski, Edward; Dickie, Matthew R.; Hoenk, Michael E.; Greer, Harold F.

2011-01-01

Flip-chip hybridization, also known as bump bonding, is a packaging technique for microelectronic devices that directly connects an active element or detector to a substrate readout face-to-face, eliminating the need for wire bonding. In order to make conductive links between the two parts, a solder material is used between the bond pads on each side. Solder bumps, composed of indium metal, are typically deposited by thermal evaporation onto the active regions of the device and substrate. While indium bump technology has been a part of the electronic interconnect process field for many years and has been extensively employed in the infrared imager industry, obtaining a reliable, high-yield process for high-density patterns of bumps can be quite difficult. Under the right conditions, a moderate hydrogen plasma exposure can raise the temperature of the indium bump to the point where it can flow. This flow can result in a desirable shape where indium will efficiently wet the metal contact pad to provide good electrical contact to the underlying readout or imager circuit. However, it is extremely important to carefully control this process as the intensity of the hydrogen plasma treatment dramatically affects the indium bump morphology. To ensure the fine-tuning of this reflow process, it is necessary to have realtime feedback on the status of the bumps. With an appropriately placed viewport in a plasma chamber, one can image a small field (a square of approximately 5 millimeters on each side) of the bumps (10-20 microns in size) during the hydrogen plasma reflow process. By monitoring the shape of the bumps in real time using a video camera mounted to a telescoping 12 magnifying zoom lens and associated optical elements, an engineer can precisely determine when the reflow of the bumps has occurred, and can shut off the plasma before evaporation or de-wetting takes place.

Fluxless flip-chip bonding using a lead-free solder bumping technique

NASA Astrophysics Data System (ADS)

Hansen, K.; Kousar, S.; Pitzl, D.; Arab, S.

2017-09-01

With the LHC exceeding the nominal instantaneous luminosity, the current barrel pixel detector (BPIX) of the CMS experiment at CERN will reach its performance limits and undergo significant radiation damage. In order to improve detector performance in high luminosity conditions, the entire BPIX is replaced with an upgraded version containing an additional detection layer. Half of the modules comprising this additional layer are produced at DESY using fluxless and lead-free bumping and bonding techniques. Sequential solder-jetting technique is utilized to wet 40-μm SAC305 solder spheres on the silicon-sensor pads with electroless Ni, Pd and immersion Au (ENEPIG) under-bump metallization (UBM). The bumped sensors are flip-chip assembled with readout chips (ROCs) and then reflowed using a flux-less bonding facility. The challenges for jetting low solder volume have been analyzed and will be presented in this paper. An average speed of 3.4 balls per second is obtained to jet about 67 thousand solder balls on a single chip. On average, 7 modules have been produced per week. The bump-bond quality is evaluated in terms of electrical and mechanical properties. The peak-bump resistance is about 17.5 mΩ. The cross-section study revealed different types of intermetallic compounds (IMC) as a result of interfacial reactions between UBM and solder material. The effect of crystalline phases on the mechanical properties of the joint is discussed. The mean shear strength per bump after the final module reflow is about 16 cN. The results and sources of yield loss of module production are reported. The achieved yield is 95%.

Thin hybrid pixel assembly with backside compensation layer on ROIC

NASA Astrophysics Data System (ADS)

Bates, R.; Buttar, C.; McMullen, T.; Cunningham, L.; Ashby, J.; Doherty, F.; Gray, C.; Pares, G.; Vignoud, L.; Kholti, B.; Vahanen, S.

2017-01-01

The entire ATLAS inner tracking system will be replaced for operation at the HL-LHC . This will include a significantly larger pixel detector of approximately 15 m2. For this project, it is critical to reduce the mass of the hybrid pixel modules and this requires thinning both the sensor and readout chips to about 150 micrometres each. The thinning of the silicon chips leads to low bump yield for SnAg bumps due to bad co-planarity of the two chips at the solder reflow stage creating dead zones within the pixel array. In the case of the ATLAS FEI4 pixel readout chip thinned to 100 micrometres, the chip is concave, with the front side in compression, with a bow of +100 micrometres at room temperature which varies to a bow of -175 micrometres at the SnAg solder reflow temperature, caused by the CTE mismatch between the materials in the CMOS stack and the silicon substrate. A new wafer level process to address the issue of low bump yield be controlling the chip bow has been developed. A back-side dielectric and metal stack of SiN and Al:Si has been deposited on the readout chip wafer to dynamically compensate the stress of the front side stack. In keeping with a 3D process the materials used are compatible with Through Silicon Via (TSV) technology with a TSV last approach which is under development for this chip. It is demonstrated that the amplitude of the correction can be manipulated by the deposition conditions and thickness of the SiN/Al:Si stack. The bow magnitude over the temperature range for the best sample to date is reduced by almost a factor of 4 and the sign of the bow (shape of the die) remains constant. Further development of the backside deposition conditions is on-going with the target of close to zero bow at the solder reflow temperature and a minimal bow magnitude throughout the temperature range. Assemblies produced from FEI4 readout wafers thinned to 100 micrometres with the backside compensation layer have been made for the first time and demonstrate bond yields close to 100%.

Fabrication of Cu-Ni mixed phase layer using DC electroplating and suppression of Kirkendall voids in Sn-Ag-Cu solder joints

NASA Astrophysics Data System (ADS)

Chee, Sang-Soo; Lee, Jong-Hyun

2014-05-01

A solderable layer concurrently containing Cu-rich and Ni-rich phases (mixed-phase layer, MPL) was fabricated by direct current electroplating under varying process conditions. Current density was considered as the main parameter to adjust the microstructure and composition of MPL during the electroplating process, and deposit thickness were evaluated as functions of plating time. As a result, it was observed that the coral-like structure that consisted of Cu-rich and Ni-rich phases grew in the thickness direction. The most desirable microstructure was obtained at a relatively low current density of 0.4 mA/cm2. In other words, the surface was the smoothest and defect-free at this current density. The electroplating rate was slightly enhanced with an increase in current density. Investigations of its solid-state reaction properties, including the formation of Kirkendall voids, were also carried out after reflow soldering with Sn-3.0 Ag-0.5 Cu solder balls. In the solid-state aging experiment at 125°C, Kirkendall voids at the normal Sn-3.0 Ag-0.5 Cu solder/Cu interface were easily formed after just 240 h. Meanwhile, the presence of an intermetallic compound (IMC) layer created in the solder/MPL interface indicated a slightly lower growth rate, and no Kirkendall voids were observed in the IMC layer even after 720 h.

Comparative Study of ENIG and ENEPIG as Surface Finishes for a Sn-Ag-Cu Solder Joint

NASA Astrophysics Data System (ADS)

Yoon, Jeong-Won; Noh, Bo-In; Jung, Seung-Boo

2011-09-01

Interfacial reactions and joint reliability of Sn-3.0Ag-0.5Cu solder with two different surface finishes, electroless nickel-immersion gold (ENIG) and electroless nickel-electroless palladium-immersion gold (ENEPIG), were evaluated during a reflow process. We first compared the interfacial reactions of the two solder joints and also successfully revealed a connection between the interfacial reaction behavior and mechanical reliability. The Sn-Ag-Cu/ENIG joint exhibited a higher intermetallic compound (IMC) growth rate and a higher consumption rate of the Ni(P) layer than the Sn-Ag-Cu/ENEPIG joint. The presence of the Pd layer in the ENEPIG suppressed the growth of the interfacial IMC layer and the consumption of the Ni(P) layer, resulting in the superior interfacial stability of the solder joint. The shear test results show that the ENIG joint fractured along the interface, exhibiting indications of brittle failure possibly due to the brittle IMC layer. In contrast, the failure of the ENEPIG joint only went through the bulk solder, supporting the idea that the interface is mechanically reliable. The results from this study confirm that the Sn-Ag-Cu/ENEPIG solder joint is mechanically robust and, thus, the combination is a viable option for a Pb-free package system.

Effect of Isothermal Aging and Thermal Cycling on Interfacial IMC Growth and Fracture Behavior of SnAgCu/Cu Joints

NASA Astrophysics Data System (ADS)

Li, Xiaoyan; Li, Fenghui; Guo, Fu; Shi, Yaowu

2011-01-01

The growth behavior of interfacial intermetallic compounds (IMCs) of SnAgCu/Cu soldered joints was investigated during the reflow process, isothermal aging, and thermal cycling with a focus on the influence of these parameters on growth kinetics. The SnAgCu/Cu soldered joints were isothermally aged at 125°C, 150°C, and 175°C while the thermal cycling was performed within the temperature ranges from -25°C to 125°C and -40°C to 125°C. It was observed that a Cu6Sn5 layer formed, followed by rapid coarsening at the solder/Cu interface during reflowing. The grain size of the interfacial Cu6Sn5 was found to increase with aging time, and the morphology evolved from scallop-like to needle-like to rod-like and finally to particles. The rod-like Ag3Sn phase was formed on the solder side in front of the previously formed Cu6Sn5 layer. However, when subject to an increase of the aging time, the Cu3Sn phase was formed at the interface of the Cu6Sn5 layer and Cu substrate. The IMC growth rate increased with aging temperature for isothermally aged joints. During thermal cycling, the thickness of the IMC layer was found to increase with the number of thermal cycles, although the growth rate was slower than that for isothermal aging. The dwell time at the high-temperature end of the thermal cycles was found to significantly influence the growth rate of the IMCs. The growth of the IMCs, for both isothermal aging and thermal cycling, was found to be Arrhenius with aging temperature, and the corresponding diffusion factor and activation energy were obtained by data fitting. The tensile strength of the soldered joints decreased with increasing aging time. Consequently, the fracture site of the soldered joints migrated from the solder matrix to the interfacial Cu6Sn5 layer. Finally, the shear strength of the joints was found to decrease with both an increase in the number of thermal cycles and a decrease in the dwell temperature at the low end of the thermal cycle.

Effect of Current Density and Plating Time on Cu Electroplating in TSV and Low Alpha Solder Bumping

NASA Astrophysics Data System (ADS)

Jung, Do-Hyun; Sharma, Ashutosh; Kim, Keong-Heum; Choo, Yong-Chul; Jung, Jae-Pil

2015-03-01

In this study, copper filling in through-silicon via (TSV) by pulse periodic reverse electroplating and low alpha solder bumping on Cu-filled TSVs was investigated. The via diameter and depth of TSV were 60 and 120 µm, respectively. The experimental results indicated that the thickness of electrodeposited copper layer increased with increasing cathodic current density and plating time. The electroplated Cu in TSV showed a typical bottom-up filling. A defectless, complete, and fast 100% Cu-filled TSV was achieved at cathodic and anodic current densities of -8 and 16 mA/cm2 for a plating time of 4 h, respectively. A sound low alpha solder ball, Sn-1.0 wt.% Ag-0.5 wt.% Cu (SAC 105) with a diameter of 83 µm and height of 66 µm was reflow processed at 245 °C on Cu-filled TSV. The Cu/solder joint interface was subjected to high temperature aging at 85 °C for 150 h, which showed an excellent bonding characteristic with minimum Cu-Sn intermetallic compounds growth.

Influence of the volume-contact area ratio on the growth behavior of the Cu-Sn intermetallic phase

NASA Astrophysics Data System (ADS)

Giddaluri, Venkatakamakshi Supraja

Solder Joints play a very important role in electronic packaging industry by serving as mechanical support and provides integrity to the device. The increasing demand for high performance, environmental and economic feasibility and miniaturization led to the development of high density interconnects. With the reduction in the size/standoff height of the solder reliability issues in the surface mount assemblies and packaging structures under various rigorous environments are becoming significant. One of the most important impact factors that affect the solder joint reliability is the growth rate IMC formed between the solder and substrate with reduction in joint size. IMC formation is required to ensure good bonding and connectivity of the device in packaging. However excess IMC growth rate is detrimental to the device from mechanical aspects due to its brittle nature. Thus there is a need to study effect the IMC growth rate behavior with the solder joint size/standoff height. In this present study, two solder joints of different standoff heights and same composition (pure Sn solder) are used subjected to reflow process at 270°C for 1--7 min to study solid liquid interfacial reaction on joint size and the same experiment is repeated with SAC alloy of composition (96.5% Sn, 3.0% Ag, 0.5% Cu) to investigate the effect of joint size and initial copper concentration on IMC growth rate. The IMC thickness of the Sn 15microm solder joint at 1 min and 7 min is found to be 1.52microm and 2.86microm respectively while that of Sn 150microm solder joint is 1.31microm and 3.16 microm. The thickness is high in low standoff height sample at the early stage of reaction with decrease in IMC growth rate as the time of reflow increases. In case of 25microm SAC alloy solder joint the IMC thickness from 1 and 7 min is found to be 2.1microm and 3.5microm while that of 250microm SAC alloy solder joint its 1.43microm and3.235microm. Similar trend is observed but the IMC thickness is more in SAC alloy compared to Pure Sn due to initial Cu concentration effect. The CGC model is applied for growth kinetics of IMC formation and is in well agreement with the experimental results. It is found that the low standoff height solder joint follow t1/3 law and high standoff height solder joint deviates from the t1/3 due to unsaturation. The pure Sn solder of two different standoff heights is also subjected to isothermal aging tests at 120°C for 0--600 hours to investigate the effect of IMC growth rate on solder joint size in solid state diffusion. It has been found that low solder joint height is having high growth rate compared to high standoff height joint and it is found to obey parabolic law and follow reaction diffusion control mechanism.

Interfacial reaction and microstructure between the Sn3Ag0.5Cu solder and Cu-Co dual-phase substrate

NASA Astrophysics Data System (ADS)

Li, Chao; Hu, Xiaowu; Jiang, Xiongxin; Li, Yulong

2018-07-01

In this study, interfacial reactions and microstructures of the Sn3Ag0.5Cu (SAC305)/Cu- xCo ( x = 0, 30 and 50 wt%) systems were investigated during reflowing at 290 °C and solid-state aging at 150 °C for various time. The effects of different contents of Co in substrate on interfacial reaction in SAC305/Cu- xCo system were discussed. It was found that the addition of Co into pure copper substrate to achieve alloying would effectively inhibit the growth of IMC layers. Comparison among the thickness of the intermetallic compound (IMC) in three kinds of SAC305/Cu-Co systems indicated that the IMC layer of SAC305/Cu joint was thicker than that of the other two types of solder joints. The composition of the SAC305/Cu IMC layers was Cu6Sn5 and Cu3Sn. Three kinds of reaction phases (Cu,Co)6Sn5, (Cu,Co)Sn2 and (Cu,Co)3Sn were found at the interfaces of the SAC305/Cu-30Co and SAC305/Cu-50Co joints. Remarkably the (Cu,Co)Sn2 phase was found adjacent to the Co-rich phase after soldering and eliminated after the aging treatment. While the (Cu,Co)3Sn phase accumulated increasingly adjacent to the substrate with the increased aging time. The results suggested that the Co content increased from 30 to 50 wt% in substrate lead to significant restraint of the growth of interfacial IMC. In addition, the thickness of the interfacial IMC layer was linear with the square root of the aging time during the aging process. The reaction rate between Sn atoms in solder and Cu, Co atoms in substrate was quite different, which lead to the fact that the interface of SAC305/Cu-Co is uneven on the side of substrate after reflowing and aging.

Intermetallic Compound Growth between Electroless Nickel/Electroless Palladium/Immersion Gold Surface Finish and Sn-3.5Ag or Sn-3.0Ag-0.5Cu Solder

NASA Astrophysics Data System (ADS)

Oda, Yukinori; Fukumuro, Naoki; Yae, Shinji

2018-04-01

Using an electroless nickel/electroless palladium/immersion gold (ENEPIG) surface finish with a thick palladium-phosphorus (Pd-P) layer of 1 μm, the intermetallic compound (IMC) growth between the ENEPIG surface finish and lead-free solders Sn-3.5Ag (SA) or Sn-3.0Ag-0.5Cu (SAC) after reflow soldering and during solid-state aging at 150°C was investigated. After reflow soldering, in the SA/ENEPIG and SAC/ENEPIG interfaces, thick PdSn4 layers of about 2 μm to 3 μm formed on the residual Pd-P layers ( 0.5 μm thick). On the SA/ENEPIG interface, Sn was detected on the upper side of the residual Pd-P layer. On the SAC/ENEPIG interface, no Sn was detected in the residual Pd-P layer, and Cu was detected in the interface between the Pd-P and PdSn4 layers. After 300 h of aging at 150°C, the residual Pd-P layers had diffused completely into the solders. In the SA/ENEPIG interface, an IMC layer consisting of Ni3Sn4 and Ni3SnP formed between the PdSn4 layer and the nickel-phosphorus (Ni-P) layer, and a (Pd,Ni)Sn4 layer formed on the lower side of the PdSn4 layer. On the SAC/ENEPIG interface, a much thinner (Pd,Ni)Sn4 layer was observed, and a (Cu,Ni)6Sn5 layer was observed between the PdSn4 and Ni-P layers. These results indicate that Ni diffusion from the Ni-P layer to the PdSn4 layer produced a thick (Pd,Ni)Sn4 layer in the SA solder case, but was prevented by formation of (Cu,Ni)6Sn5 in the SAC solder case. This causes the difference in solder joint reliability between SA/ENEPIG and SAC/ENEPIG interfaces in common, thin Pd-P layer cases.

Influence of multi-walled carbon nanotubes on melting temperature and microstructural evolution of Pb-free Sn-5Sb/Cu solder joint

NASA Astrophysics Data System (ADS)

Dele-Afolabi, T. T.; Azmah Hanim, M. A.; Norkhairunnisa, M.; Suraya, M. T.; Yusoff, H. M.

2017-09-01

In this study, the effects of multi-walled carbon nanotubes on the melting temperature and microstructural evolution of the Sn-5Sb/Cu joints are evaluated. Plain and carbon nanotubes (CNTs) reinforced Sn-5Sb solder systems with solder formulations Sn-5Sb, Sn-5Sb-0.01CNT, Sn-5Sb-0.05CNT and Sn-5Sb-0.1CNT were prepared through the powder metallurgy route and thereafter samples were subjected to thermal and microstructural evaluation. As retrieved from the DSC scans, a slight decline in the peak temperature was observed in the composite solders which is indicative of the CNTs role in exciting surface instability in the host Sn matrix. In order to prepare the solder joints and analyze the interfacial intermetallic compound (IMC) evolution, respective solder systems were placed on copper (Cu) substrate and subjected to both reflow soldering and isothermal aging (170°C) conditions. From the IMC thickness result, considerable retardation in the IMC layer growth was observed in the CNTs reinforced solder joints, especially the 0.05wt.% CNTs solder system owing to the inhibition of Sn atoms diffusion by reinforcement material.

Effect of Ni-P Plating Temperature on Growth of Interfacial Intermetallic Compound in Electroless Nickel Immersion Gold/Sn-Ag-Cu Solder Joints

NASA Astrophysics Data System (ADS)

Seo, Wonil; Kim, Kyoung-Ho; Kim, Young-Ho; Yoo, Sehoon

2018-01-01

The growth of interfacial intermetallic compound and the brittle fracture behavior of Sn-3.0Ag-0.5-Cu solder (SAC305) joints on electroless nickel immersion gold (ENIG) surface finish have been investigated using Ni-P plating solution at temperatures from 75°C to 85°C and fixed pH of 4.5. SAC305 solder balls with diameter of 450 μm were mounted on the prepared ENIG-finished Cu pads and reflowed with peak temperature of 250°C. The interfacial intermetallic compound (IMC) thickness after reflow decreased with increasing Ni-P plating temperature. After 800 h of thermal aging, the IMC thickness of the sample prepared at 85°C was higher than for that prepared at 75°C. Scanning electron microscopy of the Ni-P surface after removal of the Au layer revealed a nodular structure on the Ni-P surface. The nodule size of the Ni-P decreased with increasing Ni-P plating temperature. The Cu content near the IMC layer increased to 0.6 wt.%, higher than the original Cu content of 0.5 wt.%, indicating that Cu diffused from the Cu pad to the solder ball through the Ni-P layer at a rate depending on the nodule size. The sample prepared at 75°C with thicker interfacial IMC showed greater high-speed shear strength than the sample prepared at 85°C. Brittle fracture increased with decreasing Ni-P plating temperature.

Flip-chip assembly and reliability using gold/tin solder bumps

NASA Astrophysics Data System (ADS)

Oppermann, Hermann; Hutter, Matthias; Klein, Matthias; Reichl, Herbert

2004-09-01

Au/Sn solder bumps are commonly used for flip chip assembly of optoelectronic and RF devices. They allow a fluxless assembly which is required to avoid contamination at optical interfaces. Flip chip assembly experiments were carried out using as plated Au/Sn bumps without prior bump reflow. An RF and reliability test vehicles comprise a GaAs chip which was flip chip soldered on a silicon substrate. Temperature cycling tests with and without underfiller were performed and the results are presented. The different failure modes for underfilled and non-underfilled samples were discussed and compared. Additional reliability tests were performed with flip chip bonding by gold thermocompression for comparison. The test results and the failure modes are discussed in detail.

Utilization of Pb-free solders in MEMS packaging

NASA Astrophysics Data System (ADS)

Selvaduray, Guna S.

2003-01-01

Soldering of components within a package plays an important role in providing electrical interconnection, mechanical integrity and thermal dissipation. MEMS packages present challenges that are more complex than microelectronic packages because they are far more sensitive to shock and vibration and also require precision alignment. Soldering is used at two major levels within a MEMS package: at the die attach level and at the component attach level. Emerging environmental regulations worldwide, notably in Europe and Japan, have targeted the elimination of Pb usage in electronic assemblies, due to the inherent toxicity of Pb. This has provided the driving force for development and deployment of Pb-free solder alloys. A relatively large number of Pb-free solder alloys have been proposed by various researchers and companies. Some of these alloys have also been patented. After several years of research, the solder alloy system that has emerged is based on Sn as a major component. The electronics industry has identified different compositions for different specific uses, such as wave soldering, surface mount reflow, etc. The factors that affect choice of an appropriate Pb-free solder can be divided into two major categories, those related to manufacturing, and those related to long term reliability and performance.

Studies of material and process compatibility in developing compact silicon vapor chambers

NASA Astrophysics Data System (ADS)

Cai, Qingjun; Bhunia, Avijit; Tsai, Chialun; Kendig, Martin W.; DeNatale, Jeffrey F.

2013-06-01

The performance and long-term reliability of a silicon vapor chamber (SVC) developed for thermal management of high-power electronics critically depend on compatibility of the component materials. A hermetically sealed SVC presented in this paper is composed of bulk silicon, glass-frit as a bonding agent, lead/tin solder as an interface sealant and a copper charging tube. These materials, in the presence of a water/vapor environment, may chemically react and release noncondensable gas (NCG), which can weaken structural strength and degrade the heat transfer performance with time. The present work reports detailed studies on chemical compatibility of the components and potential solutions to avoid the resulting thermal performance degradation. Silicon surface oxidation and purification of operating liquid are necessary steps to reduce performance degradation in the transient period. A lead-based solder with its low reflow temperature is found to be electrochemically stable in water/vapor environment. High glazing temperature solidifies molecular bonding in glass-frit and mitigates PbO precipitation. Numerous liquid flushes guarantee removal of chemical residual after the charging tube is soldered to SVC. With these improvements on the SVC material and process compatibility, high effective thermal conductivity and steady heat transfer performance are obtained.

Nano-soldering of magnetically aligned three-dimensional nanowire networks.

PubMed

Gao, Fan; Gu, Zhiyong

2010-03-19

It is extremely challenging to fabricate 3D integrated nanostructures and hybrid nanoelectronic devices. In this paper, we report a simple and efficient method to simultaneously assemble and solder nanowires into ordered 3D and electrically conductive nanowire networks. Nano-solders such as tin were fabricated onto both ends of multi-segmented nanowires by a template-assisted electrodeposition method. These nanowires were then self-assembled and soldered into large-scale 3D network structures by magnetic field assisted assembly in a liquid medium with a high boiling point. The formation of junctions/interconnects between the nanowires and the scale of the assembly were dependent on the solder reflow temperature and the strength of the magnetic field. The size of the assembled nanowire networks ranged from tens of microns to millimeters. The electrical characteristics of the 3D nanowire networks were measured by regular current-voltage (I-V) measurements using a probe station with micropositioners. Nano-solders, when combined with assembling techniques, can be used to efficiently connect and join nanowires with low contact resistance, which are very well suited for sensor integration as well as nanoelectronic device fabrication.

Roles of interfacial reaction on mechanical properties of solder interfaces

NASA Astrophysics Data System (ADS)

Liu, Pilin

This study investigated roles of interfacial reaction in fracture and fatigue of solder interconnects. The interfacial reaction phases in the as-reflowed and after aging were examined by cross-sectional transmission electron microscopy (TEM) while interfacial mechanical properties were determined from a flexural peel fracture mechanics technique. Because of their widespread uses in microelectronic packaging, SnPb solder interfaces, and Bi-containing Pb-free solder interfaces were chosen as the subjects of this study. In the interfacial reaction study, we observed a complicated micro structural evolution during solid-state aging of electroless-Ni(P)/SnPb solder interconnects. In as-reflowed condition, the interfacial reaction produced Ni3Sn 4 and P-rich layers. Following overaging, the interfacial microstructure degenerated into a complex multilayer structure consisting of multiple layers of Ni-Sn compounds and transformed Ni-P phases. In SnPb solder interfacial system, fatigue study showed that the overaging of the high P electroless Ni-P/SnPb interconnects resulted in a sharp reduction in the fatigue resistance of the interface in the high crack growth rate regime. Fracture mechanism analysis indicated that the sharp drop in fatigue resistance was triggered by the brittle fracture of the Ni3Sn2 intermetallic phase developed at the overaged interface. The fatigue behavior was strongly dependent on P concentration in electroless Ni. Kirkendall voids were found in the interfacial region after aging, but they did not cause premature fracture of the solder interfaces. In Bi-containing solder interfacial system, we found that Bi segregated to the Cu-intermetallic interface during aging in SnBi/Cu interconnect. This caused serious embrittlement of Sn-Bi/Cu interface. Further aging induced numerous voids along the Cu3Sn/Cu interface. These interfacial voids were different from Kirkendall voids. Their formation was explained on basis of vacancy condensation at the interface as the Bi segregants reduced the number of effective Cu vacancy sink sites and enhanced void nucleation at the interface. The Bi segregation was avoided by replacing the Cu metallization with Ni. It was found that Bi developed a concentration gradient in the Ni 3Sn4 during interfacial reaction, with the Bi concentration falling off to zero as the Ni/IMC interface was approached. Therefore, the inhibition of Bi segregation by Ni was due to the inability of Bi to reach Ni/IMC interface.

Effect of the Silver Content of SnAgCu Solder on the Interfacial Reaction and on the Reliability of Angle Joints Fabricated by Laser-Jet Soldering

NASA Astrophysics Data System (ADS)

Ji, Hongjun; Ma, Yuyou; Li, Mingyu; Wang, Chunqing

2015-02-01

The silver content of lead-free solders affects their microstructure, the interfacial reaction, and the performance of the joints in reliability tests. In this study, Sn3.0Ag0.5Cu (wt.%, SAC305) and Sn1.0Ag0.5Cu (wt.%, SAC105) solder balls of diameter 55 μm were reflowed on gold surface pads by laser-jet soldering. It was found that four types of layered intermetallic compound (IMC) were formed at the interfaces; these were Au5Sn/AuSn, AuSn, AuSn2, and AuSn4 from the pad side to the solder matrix. The Au5Sn/AuSn eutectic region, thickness 400 nm, formed because of the high cooling rate induced by the laser-jet soldering. During high-temperature storage tests, the silver became segregated at the interfaces between the Au-Sn IMC and the solder matrix, resulting in inhibition of IMC growth in SAC305 joints, the shear strengths of which were higher than those of SAC105 joints. In mechanical drop tests, however, percentage failure of the SAC305 joints was twice that of the SAC105 joints.

Measurements of True Leak Rates of MEMS Packages

PubMed Central

Han, Bongtae

2012-01-01

Gas transport mechanisms that characterize the hermetic behavior of MEMS packages are fundamentally different depending upon which sealing materials are used in the packages. In metallic seals, gas transport occurs through a few nanoscale leak channels (gas conduction) that are produced randomly during the solder reflow process, while gas transport in polymeric seals occurs through the bulk material (gas diffusion). In this review article, the techniques to measure true leak rates of MEMS packages with the two sealing materials are described and discussed: a Helium mass spectrometer based technique for metallic sealing and a gas diffusion based model for polymeric sealing. PMID:22736994

Reliability of Tin Silver Copper and mixed solders under variable loading conditions

NASA Astrophysics Data System (ADS)

Jaradat, Younis

Industry use of lead free solder joints necessitates accurate modeling in predicting life in service. Yet, current extrapolations of accelerated test results do not actuate realistic conditions. This research focuses on joint properties of Pb-mixed and Pb-free solder alloys in order to explain material behavior subject to certain test conditions, i.e., varying cycling amplitudes. Additionally, this research will begin with extensive studies on backward compatible solder joints from the material's behavior to its reliability under displacement and load controlled fatigue tests. We address the evolution of the joint's microstructure ergo its properties and performance (mixed solder joints). The present work reports results of reflowing 30 mil SAC305 balls onto Cu, and ENIG coated BGA pads with different amounts of SnPb paste, aging and/or cycling the joints and inspecting the microstructure by cross polarizer microscopy and SEM. We found that the addition of small amounts of Pb had significant effects on solidification during cool-down from reflow, and consequently the initial microstructure. In terms of the varying cycling amplitude study, we note how realistic service conditions are almost never well approximated by cycling with fixed amplitudes. Recent results have demonstrated the consistent breakdown of common damage accumulation rules. In isothermal cycling tests the remaining life, after a step-down in amplitude, was invariably shorter than predicted by such a rule, while a step-up tended to have the opposite effect. The present work offers a mechanistic explanation for this and the basis for a practical approach to the assessment of life under service conditions. Realistic BGA joints were cycled individually in a micromechanical tester, monitoring the solder stiffness and the inelastic energy deposition. Cycling was seen to first cause rapid hardening, followed by leveling off in a 'cyclic saturation' stage and eventually the initiation and growth of a crack until failure. A temporary increase in amplitude during cycling caused a lasting reduction in hardness, and thus enhanced inelastic energy deposition and damage evolution, after the fact. This factor dominates during repeated increases and decreases, eventually shortening the remaining life dramatically

Cu6Sn5 Whiskers Precipitated in Sn3.0Ag0.5Cu/Cu Interconnection in Concentrator Silicon Solar Cells Solder Layer

PubMed Central

Zhang, Liang; Liu, Zhi-quan; Yang, Fan; Zhong, Su-juan

2017-01-01

Cu6Sn5 whiskers precipitated in Sn3.0Ag0.5Cu/Cu interconnection in concentrator silicon solar cells solder layer were found and investigated after reflow soldering and during aging. Ag3Sn fibers can be observed around Cu6Sn5 whiskers in the matrix microstructure, which can play an active effect on the reliability of interconnection. Different morphologies of Cu6Sn5 whiskers can be observed, and hexagonal rod structure is the main morphology of Cu6Sn5 whiskers. A hollow structure can be observed in hexagonal Cu6Sn5 whiskers, and a screw dislocation mechanism was used to represent the Cu6Sn5 growth. Based on mechanical property testing and finite element simulation, Cu6Sn5 whiskers were regarded as having a negative effect on the durability of Sn3.0Ag0.5Cu/Cu interconnection in concentrator silicon solar cells solder layer. PMID:28772686

Thermomechanical behavior of tin-rich (lead-free) solders

NASA Astrophysics Data System (ADS)

Sidhu, Rajen Singh

In order to adequately characterize the behavior of ball-grid-array (BGA) Pb-free solder spheres in electronic devices, the microstructure and thermomechanical behavior need to be studied. Microstructure characterization of pure Sn, Sn-0.7Cu, Sn-3.5Ag, and Sn-3.9Ag-0.7Cu alloys was conducted using optical microscopy, scanning electron microscopy, transmission electron microscopy, image analysis, and a novel serial sectioning 3D reconstruction process. Microstructure-based finite-element method (FEM) modeling of deformation in Sn-3.5Ag alloy was conducted, and it will be shown that this technique is more accurate when compared to traditional unit cell models for simulating and understanding material behavior. The effect of cooling rate on microstructure and creep behavior of bulk Sn-rich solders was studied. The creep behavior was evaluated at 25, 95, and 120°C. Faster cooling rates were found to increase the creep strength of the solders due to refinement of the solder microstructure. The creep behavior of Sn-rich single solder spheres reflowed on Cu substrates was studied at 25, 60, 95, and 130°C. Testing was conducted using a microforce testing system, with lap-shear geometry samples. The solder joints displayed two distinct creep behaviors: (a) precipitation-strengthening (Sn-3.5Ag and Sn-3.9Ag-0.7Cu) and (b) power law creep accommodated by grain boundary sliding (GBS) (Sn and Sn-0.7Cu). The relationship between microstructural features (i.e. intermetallic particle size and spacing), stress exponents, threshold stress, and activation energies are discussed. The relationship between small-length scale creep behavior and bulk behavior is also addressed. To better understand the damage evolution in Sn-rich solder joints during thermal fatigue, the local damage will be correlated to the cyclic hysteresis behavior and crystal orientations present in the Sn phase of solder joints. FEM modeling will also be utilized to better understand the macroscopic and local strain response of the lap shear geometry.

Scalable Manufacturing of Solderable and Stretchable Physiologic Sensing Systems.

PubMed

Kim, Yun-Soung; Lu, Jesse; Shih, Benjamin; Gharibans, Armen; Zou, Zhanan; Matsuno, Kristen; Aguilera, Roman; Han, Yoonjae; Meek, Ann; Xiao, Jianliang; Tolley, Michael T; Coleman, Todd P

2017-10-01

Methods for microfabrication of solderable and stretchable sensing systems (S4s) and a scaled production of adhesive-integrated active S4s for health monitoring are presented. S4s' excellent solderability is achieved by the sputter-deposited nickel-vanadium and gold pad metal layers and copper interconnection. The donor substrate, which is modified with "PI islands" to become selectively adhesive for the S4s, allows the heterogeneous devices to be integrated with large-area adhesives for packaging. The feasibility for S4-based health monitoring is demonstrated by developing an S4 integrated with a strain gauge and an onboard optical indication circuit. Owing to S4s' compatibility with the standard printed circuit board assembly processes, a variety of commercially available surface mount chip components, such as the wafer level chip scale packages, chip resistors, and light-emitting diodes, can be reflow-soldered onto S4s without modifications, demonstrating the versatile and modular nature of S4s. Tegaderm-integrated S4 respiration sensors are tested for robustness for cyclic deformation, maximum stretchability, durability, and biocompatibility for multiday wear time. The results of the tests and demonstration of the respiration sensing indicate that the adhesive-integrated S4s can provide end users a way for unobtrusive health monitoring. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Recrystallization Behavior in SAC305 and SAC305 + 3.0POSS Solder Joints Under Thermal Shock

NASA Astrophysics Data System (ADS)

Han, Jing; Gu, Penghao; Ma, Limin; Guo, Fu; Liu, Jianping

2018-04-01

Sn-3.0Ag-0.5Cu (SAC305) and SAC305 + 3.0 polyhedral oligomeric silsesquioxanes (POSS) ball grid array (BGA) assemblies have been prepared, observed, and subjected to thermal shock. The microstructure and grain orientation evolution of the solder joints located at the same position of the package were characterized by scanning electron microscopy and electron backscattering diffraction, respectively. The results showed that the microstructure of the solder joints was refined by addition of POSS particles. In addition, compared with the single-grained or tricrystal joints normally observed in SAC305 BGA solder joints, the frequency of single-grained as-reflowed SAC305 + 3.0POSS BGA joints was greatly reduced, and the solder joints were typically composed of multicrystals with orientations separated by high-angle grain boundaries. These multicrystal joints appear to be obtained by dominant tricrystals or double tricrystals with deviation of the preferred [110] and [1\\bar{1}0] growth directions of Sn dendrites in Sn-Ag-based solder alloys during solidification from the melt. After 928 thermal shock cycles, the SAC305 solder joint had large-area recrystallization and cracks in contrast to the SAC305 + 3.0POSS solder joint located at the same position of the package, indicating that addition of POSS to SAC305 solder joints may contribute to postponement of recrystallization and subsequent crack initiation and propagation along recrystallized grain boundaries by pinning grain boundaries and movement of dislocations. This finding also confirms the double tricrystal solidification twinning nucleation behavior in Pb-free solder joints.

Development of True Time Delay Circuits

DTIC Science & Technology

2014-06-13

public release Distribution is unlimited DATA SHEET SKY65014-70LF: 0.1-7.0 GHz InGaP Cascadable Amplifier Applications • Wireless infrastructure: WLAN ...decoupling network out of band. For low frequency applications , R1 may be used to conveniently limit supply current on the Evaluation Board. The Evaluation...additional information, refer to the Skyworks Application Note, Solder Reflow Information, document number 200164. Care must be taken when attaching this

An analysis of the pull strength behaviors of fine-pitch, flip chip solder interconnections using a Au-Pt-Pd thick film conductor on Low-Temperature, Co-fired Ceramic (LTCC) substrates.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Uribe, Fernando R.; Kilgo, Alice C.; Grazier, John Mark

2008-09-01

The assembly of the BDYE detector requires the attachment of sixteen silicon (Si) processor dice (eight on the top side; eight on the bottom side) onto a low-temperature, co-fired ceramic (LTCC) substrate using 63Sn-37Pb (wt.%, Sn-Pb) in a double-reflow soldering process (nitrogen). There are 132 solder joints per die. The bond pads were gold-platinum-palladium (71Au-26Pt-3Pd, wt.%) thick film layers fired onto the LTCC in a post-process sequence. The pull strength and failure modes provided the quality metrics for the Sn-Pb solder joints. Pull strengths were measured in both the as-fabricated condition and after exposure to thermal cycling (-55/125 C; 15more » min hold times; 20 cycles). Extremely low pull strengths--referred to as the low pull strength phenomenon--were observed intermittently throughout the product build, resulting in added program costs, schedule delays, and a long-term reliability concern for the detector. There was no statistically significant correlation between the low pull strength phenomenon and (1) the LTCC 'sub-floor' lot; (2) grit blasting the LTCC surfaces prior to the post-process steps; (3) the post-process parameters; (4) the conductor pad height (thickness); (5) the dice soldering assembly sequence; or (5) the dice pull test sequence. Formation of an intermetallic compound (IMC)/LTCC interface caused by thick film consumption during either the soldering process or by solid-state IMC formation was not directly responsible for the low-strength phenomenon. Metallographic cross sections of solder joints from dice that exhibited the low pull strength behavior, revealed the presence of a reaction layer resulting from an interaction between Sn from the molten Sn-Pb and the glassy phase at the TKN/LTCC interface. The thick film porosity did not contribute, explicitly, to the occurrence of reaction layer. Rather, the process of printing the very thin conductor pads was too sensitive to minor thixotropic changes to ink, which resulted in inconsistent proportions of metal and glassy phase particles present during the subsequent firing process. The consequences were subtle, intermittent changes to the thick film microstructure that gave rise to the reaction layer and, thus, the low pull strength phenomenon. A mitigation strategy would be the use of physical vapor deposition (PVD) techniques to create thin film bond pads; this is multi-chip module, deposited (MCM-D) technology.« less

Reliability of CGA/LGA/HDI Package Board/Assembly (Final Report)

NASA Technical Reports Server (NTRS)

Ghaffaroam. Reza

2014-01-01

Package manufacturers are now offering commercial-off-the-shelf column grid array (COTS CGA) packaging technologies in high-reliability versions. Understanding the process and quality assurance (QA) indicators for reliability are important for low-risk insertion of these advanced electronics packages. The previous reports, released in January of 2012 and January of 2013, presented package test data, assembly information, and reliability evaluation by thermal cycling for CGA packages with 1752, 1517, 1509, and 1272 inputs/outputs (I/Os) and 1-mm pitch. It presented the thermal cycling (-55C either 100C or 125C) test results for up to 200 cycles. This report presents up to 500 thermal cycles with quality assurance and failure analysis evaluation represented by optical photomicrographs, 2D real time X-ray images, dye-and-pry photomicrographs, and optical/scanning electron Microscopy (SEM) cross-sectional images. The report also presents assembly challenge using reflowing by either vapor phase or rework station of CGA and land grid array (LGA) versions of three high I/O packages both ceramic and plastic configuration. A new test vehicle was designed having high density interconnect (HDI) printed circuit board (PCB) with microvia-in-pad to accommodate both LGA packages as well as a large number of fine pitch ball grid arrays (BGAs). The LGAs either were assembled onto HDI PCB as an LGA or were solder paste print and reflow first to form solder dome on pads before assembly. Both plastic BGAs with 1156 I/O and ceramic LGAs were assembled. It also presented the X-ray inspection results as well as failures due to 200 thermal cycles. Lessons learned on assembly of ceramic LGAs are also presented.

Rate dependent strengths of some solder joints

NASA Astrophysics Data System (ADS)

Williamson, D. M.; Field, J. E.; Palmer, S. J. P.; Siviour, C. R.

2007-08-01

The shear strengths of three lead-free solder joints have been measured over the range of loading rates 10-3 to ~105 mm min-1. Binary (SnAg), ternary (SnAgCu) and quaternary (Castin: SnAgCuSb) alloys have been compared to a conventional binary SnPb solder alloy. Results show that at loading rates from 10-3 to 102 mm min-1, all four materials exhibit a linear relationship between the shear strength and the loading rate when the data are plotted on a log-log plot. At the highest loading rate of 105 mm min-1, the strengths of the binary alloys were in agreement with extrapolations made from the lower loading rate data. In contrast, the strengths of the higher order alloys were found to be significantly lower than those predicted by extrapolation. This is explained by a change in failure mechanism on the part of the higher order alloys. Similar behaviour was found in measurements of the tensile strengths of solder joints using a novel high-rate loading tensile test. Optical and electron microscopy were used to examine the microstructures of interest in conjunction with energy dispersive x-ray analysis for elemental identification. The effect of artificial aging and reflow of the solder joints is also reported.

Reflow process stabilization by chemical characteristics and process conditions

NASA Astrophysics Data System (ADS)

Kim, Myoung-Soo; Park, Jeong-Hyun; Kim, Hak-Joon; Kim, Il-Hyung; Jeon, Jae-Ha; Gil, Myung-Goon; Kim, Bong-Ho

2002-07-01

With the shrunken device rule below 130nm, the patterning of smaller contact hole with enough process margin is required for mass production. Therefore, shrinking technology using thermal reflow process has been applied for smaller contact hole formation. In this paper, we have investigated the effects of chemical characteristics such as molecular weight, blocking ratio of resin, cross-linker amount and solvent type with its composition to reflow process of resist and found the optimized chemical composition for reflow process applicable condition. And several process conditions like resist coating thickness and multi-step thermal reflow method have been also evaluated to stabilize the pattern profile and improve CD uniformity after reflow process. From the experiment results, it was confirmed that the effect of crosslinker in resist to reflow properties such as reflow temperature and reflow rate were very critical and it controlled the pattern profile during reflow processing. And also, it showed stable CD uniformity and improved resist properties for top loss, film shrinkage and etch selectivity. The application of lower coating thickness of resist induced symmetric pattern profile even at edge with wider process margin. The introduction of two-step baking method for reflow process showed uniform CD value, also. It is believed that the application of resist containing crosslinker and optimized process conditions for smaller contact hole patterning is necessary for the mass production with a design rule below 130nm.

Effects of Surface Finishes and Current Stressing on Interfacial Reaction Characteristics of Sn-3.0Ag-0.5Cu Solder Bumps

NASA Astrophysics Data System (ADS)

Kim, Jae-Myeong; Jeong, Myeong-Hyeok; Yoo, Sehoon; Park, Young-Bae

2012-04-01

The effects of surface finishes on the in situ interfacial reaction characteristics of ball grid array (BGA) Sn-3.0Ag-0.5Cu lead-free solder bumps were investigated under annealing and electromigration (EM) test conditions of 130°C to 175°C with 5.0 × 103 A/cm2. During reflow and annealing, (Cu,Ni)6Sn5 intermetallic compound (IMC) formed at the interface of electroless nickel immersion gold (ENIG) finish. In the case of both immersion Sn and organic solderability preservative (OSP) finishes, Cu6Sn5 and Cu3Sn IMCs formed. Overall, the IMC growth velocity of ENIG was much lower than that of the other finishes. The activation energies of total IMCs were found to be 0.52 eV for ENIG, 0.78 eV for immersion Sn, and 0.72 eV for OSP. The ENIG finish appeared to present an effective diffusion barrier between the Cu substrate and the solder, which leads to better EM reliability in comparison with Cu-based pad systems. The failure mechanisms were explored in detail via in situ EM tests.

Evaluation of Electroplated Co-P Film as Diffusion Barrier Between In-48Sn Solder and SiC-Dispersed Bi2Te3 Thermoelectric Material

NASA Astrophysics Data System (ADS)

Li, Siyang; Yang, Donghua; Tan, Qing; Li, Liangliang

2015-06-01

The diffusion barrier property of Co-P film as a buffer layer between SiC-dispersed Bi2Te3 bulk material and In-48Sn solder was investigated. A Co-P film with thickness of ~6 µm was electroplated on SiC-dispersed Bi2Te3 substrate, joined with In-48Sn solder by a reflow process, and annealed at 100°C for up to 625 h. The formation and growth kinetics of intermetallic compounds (IMCs) at the interface between the In-48Sn and substrate were studied using transmission electron microscopy and scanning electron microscopy with energy-dispersive x-ray spectroscopy. The results showed that crystalline Co(In,Sn)3 formed as an irregular layer adjacent to the solder side at the solder/Co-P interface due to diffusion of Co towards the solder, and a small amount of amorphous Co45P13In12Sn30 appeared at the Co-P side because of diffusion of In and Sn into Co-P. The growth of Co(In,Sn)3 and Co45P13In12Sn30 during solid-state aging was slow, being controlled by interfacial reaction and diffusion, respectively. For comparison, In-48Sn/Bi2Te3-SiC joints were prepared and the IMCs in the joints analyzed. Without a diffusion barrier, In penetrated rapidly into the substrate, which led to the formation of amorphous In x Bi y phase in crystalline In4Te3 matrix. These IMCs grew quickly with prolongation of the annealing time, and their growth was governed by volume diffusion of elements. The experimental data demonstrate that electroplated Co-P film is an effective diffusion barrier for use in Bi2Te3-based thermoelectric modules.

Study on Subgrain Rotation Behavior at Different Interfaces of a Solder Joint During Thermal Shock

NASA Astrophysics Data System (ADS)

Han, Jing; Tan, Shihai; Guo, Fu

2016-12-01

In order to investigate subgrain rotation behavior in the recrystallized region of lead-free solder joints, a ball grid array (BGA) specimen with a cross-sectioned edge row was thermally shocked. Electron backscattered diffraction (EBSD) was used to obtain the microstructure and orientations of Sn grains or subgrains in as-reflowed and thermally shocked conditions. Orientation imaging microscopy (OIM) showed that several subgrains were formed at the tilted twin grain boundaries, near the chip side and near the printed circuit board (PCB) side after 200 thermal shocks due to a highly mismatched coefficient of thermal expansion (CTE) of twin grains. Also, subgrains formed at the chip side and PCB side in the solder joint were selected to research the grain rotation behavior in lead-free solder joints. The analysis of subgrain rotation also indicated that the rotation behavior of subgrains was different between the chip side and PCB side. It was closely related with the large different crystal orientations between the chip side and PCB side. Furthermore, electron backscattered patterns (EBSPs) at several parts of the joint were not obtained after 300 thermal shocks due to the serious deformation caused by mismatched CTE during thermal shock. But 4 subgrains were selected and compared with that of the initial state and 200-thermal shock conditions. The results showed that the subgrains at the chip side were also rotated around the Sn [101] and [001] axes and the subgrains at the PCB side were also rotated around the Sn [100] axis, which indicated a continuous process of subgrain rotation.

Programmable Multi-Chip Module

DOEpatents

Kautz, David; Morgenstern, Howard; Blazek, Roy J.

2005-05-24

A multi-chip module comprising a low-temperature co-fired ceramic substrate having a first side on which are mounted active components and a second side on which are mounted passive components, wherein this segregation of components allows for hermetically sealing the active components with a cover while leaving accessible the passive components, and wherein the passive components are secured using a reflow soldering technique and are removable and replaceable so as to make the multi-chip module substantially programmable with regard to the passive components.

Programmable Multi-Chip Module

DOEpatents

Kautz, David; Morgenstern, Howard; Blazek, Roy J.

2004-11-16

A multi-chip module comprising a low-temperature co-fired ceramic substrate having a first side on which are mounted active components and a second side on which are mounted passive components, wherein this segregation of components allows for hermetically sealing the active components with a cover while leaving accessible the passive components, and wherein the passive components are secured using a reflow soldering technique and are removable and replaceable so as to make the multi-chip module substantially programmable with regard to the passive components.

Programmable multi-chip module

DOEpatents

Kautz, David; Morgenstern, Howard; Blazek, Roy J.

2004-03-02

A multi-chip module comprising a low-temperature co-fired ceramic substrate having a first side on which are mounted active components and a second side on which are mounted passive components, wherein this segregation of components allows for hermetically sealing the active components with a cover while leaving accessible the passive components, and wherein the passive components are secured using a reflow soldering technique and are removable and replaceable so as to make the multi-chip module substantially programmable with regard to the passive components.

Ultraminiature Broadband Light Source and Method of Manufacturing Same

NASA Technical Reports Server (NTRS)

Tuma, Margaret L. (Inventor); Collura, Joseph S. (Inventor); Helvajian, Henry (Inventor); Pocha, Michael D. (Inventor); Meyer, Glenn A. (Inventor); McConaghy, Charles F. (Inventor); Olsen, Barry L. (Inventor); Hansen, William W. (Inventor)

2010-01-01

An ultraminiature light source using a double-spiral shaped tungsten filament includes end contact portions which are separated to allow for radial and length-wise unwinding of the spiral. The double-spiral filament is spaced relatively far apart at the end portions thereof so that contact between portions of the filament upon expansion is avoided. The light ource is made by fabricating a double-spiral ultraminiature tungsten filament from tungsten foil and housing the filament in a ceramic package having a reflective bottom and a well wherein the filament is suspended. A vacuum furnace brazing process attaches the filament to contacts of the ceramic package. Finally, a cover with a transparent window is attached onto the top of the ceramic package by solder reflow in a second vacuum furnace process to form a complete hermetically sealed package.

Ultraminiature broadband light source with spiral shaped filament

NASA Technical Reports Server (NTRS)

McConaghy, Charles F. (Inventor); Olsen, Barry L. (Inventor); Tuma, Margaret L. (Inventor); Collura, Joseph S. (Inventor); Pocha, Michael D. (Inventor); Helvajian, Henry (Inventor); Meyer, Glenn A. (Inventor); Hansen, William W (Inventor)

2012-01-01

An ultraminiature light source using a double-spiral shaped tungsten filament includes end contact portions which are separated to allow for radial and length-wise unwinding of the spiral. The double-spiral filament is spaced relatively far apart at the end portions thereof so that contact between portions of the filament upon expansion is avoided. The light source is made by fabricating a double-spiral ultraminiature tungsten filament from tungsten foil and housing the filament in a ceramic package having a reflective bottom and a well wherein the filament is suspended. A vacuum furnace brazing process attaches the filament to contacts of the ceramic package. Finally, a cover with a transparent window is attached onto the top of the ceramic package by solder reflow in a second vacuum furnace process to form a complete hermetically sealed package.

Silver flip chip interconnect technology and solid state bonding

NASA Astrophysics Data System (ADS)

Sha, Chu-Hsuan

In this dissertation, fluxless transient liquid phase (TLP) bonding and solid state bonding between thermal expansion mismatch materials have been developed using Ag-In binary systems, pure Au, Ag, and Cu-Ag composite. In contrast to the conventional soldering process, fluxless bonding technique eliminates any corrosion and contamination problems caused by flux. Without flux, it is possible to fabricate high quality joints in large bonding areas where the flux is difficult to clean entirely. High quality joints are crucial to bonding thermal expansion mismatch materials since shear stress develops in the bonded pair. Stress concentration at voids in joints could increases breakage probability. In addition, intermetallic compound (IMC) formation between solder and underbump metallurgy (UBM) is essential for interconnect joint formation in conventional soldering process. However, the interface between IMC and solder is shown to be the weak interface that tends to break first during thermal cycling and drop tests. In our solid state bonding technique, there is no IMC involved in the bonding between Au to Au, Ag and Cu, and Ag and Au. All the reliability issues related to IMC or IMC growth is not our concern. To sum up, ductile bonding media, such as Ag or Au, and proper metallic layered structure are utilized in this research to produce high quality joints. The research starts with developing a low temperature fluxless bonding process using electroplated Ag/In/Ag multilayer structures between Si chip and 304 stainless steel (304SS) substrate. Because the outer thin Ag layer effectively protects inner In layer from oxidation, In layer dissolves Ag layer and joints to Ag layer on the to-be-bonded Si chip when temperature reaches the reflow temperature of 166ºC. Joints consist of mainly Ag-rich Ag-In solid solution and Ag2In. Using this fluxless bonding technique, two 304SS substrates can be bonded together as well. From the high magnification SEM images taken at cross-section, there is no void or gap observed. The new bonding technique presented should be valuable in packaging high power electronic devices for high temperature operations. It should also be useful to bond two 304SS parts together at low bonding temperature of 190ºC. Solid state bonding technique is then introduced to bond semiconductor chips, such as Si, to common substrates, such as Cu or alumina, using pure Ag and Au at a temperature matching the typical reflow temperature used in packaging industries, 260°C. In bonding, we realize the possibilities of solid state bonding of Au to Au, Au to Ag, and Ag to Cu. The idea comes from that Cu, Ag, and Au are located in the same column on periodic table, meaning that they have similar electronic configuration. They therefore have a better chance to share electrons. Also, the crystal lattice of Cu, Ag, and Au is the same, face-centered cubic. In the project, the detailed bonding mechanism is beyond the scope and here we determine the bonding by the experimental result. Ag is chosen as the joint material because of its superior physical properties. It has the highest electrical and thermal conductivities among all metals. It has low yield strength and is relatively ductile. Au is considered as well because its excellent ductility and fatigue resistance. Thus, the Ag or Au joints can deform to accommodate the shear strain caused by CTE mismatch between Si and Cu. Ag and Au have melting temperatures higher than 950°C, so the pure Ag or Au joints are expected to sustain in high operating temperature. The resulting joints do not contain any intermetallic compound. Thus, all reliability issues associated with intermetallic growth in commonly used solder joints do not exist anymore. We finally move to the applications of solid state Ag bonding in flip chip interconnects design. At present, nearly all large-scale integrated circuit (IC) chips are packaged with flip-chip technology. This means that the chip is flipped over and the active (front) side is connected to the package using a large number of tiny solder joints, which provide mechanical support, electrical connection, and heat conduction. For chip-to-package level interconnects, a challenge is the severe mismatch in coefficient of thermal expansion (CTE) between chips and package substrates. The interconnect material thus needs to be compliant to deal with the CTE mismatch. At present, nearly all flip-chip interconnects in electronic industries are made of lead-free Sn-based solders. Soft solders are chosen due to high ductility, low yield strength, relatively low melting temperature, and reasonably good electrical and thermal conductivities. In the never ending scaling down trend, more and more transistors are placed on the same Si chip size. This results in larger pin-out numbers and smaller solder joints. According to International Technology Roadmap for Semiconductors (ITRS), by 2018, the pitch in flip-chip interconnects will become smaller than 70mum for high performance applications. Two problems occur. The first is increase in shear strain. The aspect ratio of flip-chip joints is constrained to 0.7 because it goes through molten phase in the reflow process. Therefore, smaller joints become shorter as well, resulting in larger shear strain arising from CTE mismatch between Si chips and package substrates. The second is increase in stress in the joints. Since intermetallic (IMC) thickness in the joint does not scale down with joint size, ratio of IMC thickness to joint height increases. This further enlarges the shear stress because the IMC does not deform as the soft solder does to accommodate CTE mismatch. In this research, the smallest dimension we achieve for Ag flip chip interconnect joint is 15mum in diameter. The ten advantages of Ag flip chip interconnect technology can be identified as (a) High electrical conductivity, 7.7 times of that of Pb-free solders, (b) High thermal conductivity, 5.2 times of that of Pb-free solders, (c) Completely fluxless, (d) No IMCs; all reliability issues associated with IMC and IMC growth do not exist, (e) Ag is very ductile and can manage CTE mismatch between chips and packages, (f) Ag joints can sustain at very high operation temperature because Ag has high melting temperature of 961°C, (g) No molten phase involved; the bump can better keep its shape and geometry, (h) No molten phase involved; bridging of adjacent bumps is less likely to occur, i. Aspect ratio of bumps can be made greater than 1, (j) The size of the bumps is only limited by the lithographic process. Cu-Ag composite flip chip interconnect joints is developed based on three reasons. The first is lower material cost. The second is to strengthen the columns because the yield strength of Cu is 6 times of that of Ag. The third is to avoid possible Ag migration between Ag electrodes under voltage at temperatures above 250°C. This Cu-Ag composite design presents a solution in the path to the scale down roadmap.

A novel low temperature soft reflow process for the fabrication of deep-submicron (<0.35 μm) T-gate pseudomorphic high electron mobility transistor structures

NASA Astrophysics Data System (ADS)

Ian, Ka Wa; Exarchos, Michael; Missous, Mohamed

2013-02-01

We report a new and simple low temperature soft reflow process using solvent vapour. The combination of this soft reflow and conventional i-line lithography enables low cost, highly efficient fabrication at the deep-submicron scale. Compared to the conventional thermal reflow process, the key benefits of the new soft reflow process are its low temperature operation (<50 °C), greater shrinkage of the structure size (up to 75%) and better controllability. Gate openings reflowed from 1 μm to 250 nm have been routinely and reproducibly achieved by utilizing the saturation characteristics of the process. The feasibility of this soft reflow process is demonstrated in the fabrication of a 350 nm T-gate pseudomorphic high electron mobility transistor. By shrinking the gate length by a factor of three (from a 1 μm initial opening), the output current is improved by 60% (500 mA mm-1 from 300 mA mm-1) and fT and fMAX are increased to 70 GHz (from 20 GHz) and 120 GHz (from 40 GHz) respectively. The proposed soft reflow could potentially be applied on other compatible substrates such as polymer based material for organic or thin film devices, potentially leading to many new possible applications.

3D Printing of Ball Grid Arrays

NASA Astrophysics Data System (ADS)

Sinha, Shayandev; Hines, Daniel; Dasgupta, Abhijit; Das, Siddhartha

Ball grid arrays (BGA) are interconnects between an integrated circuit (IC) and a printed circuit board (PCB), that are used for surface mounting electronic components. Typically, lead free alloys are used to make solder balls which, after a reflow process, establish a mechanical and electrical connection between the IC and the PCB. High temperature processing is required for most of these alloys leading to thermal shock causing damage to ICs. For producing flexible circuits on a polymer substrate, there is a requirement for low temperature processing capabilities (around 150 C) and for reducing strain from mechanical stresses. Additive manufacturing techniques can provide an alternative methodology for fabricating BGAs as a direct replacement for standard solder bumped BGAs. We have developed aerosol jet (AJ) printing methods to fabricate a polymer bumped BGA. As a demonstration of the process developed, a daisy chain test chip was polymer bumped using an AJ printed ultra violet (UV) curable polymer ink that was then coated with an AJ printed silver nanoparticle laden ink as a conducting layer printed over the polymer bump. The structure for the balls were achieved by printing the polymer ink using a specific toolpath coupled with in-situ UV curing of the polymer which provided good control over the shape, resulting in well-formed spherical bumps on the order of 200 um wide by 200 um tall for this initial demonstration. A detailed discussion of the AJ printing method and results from accelerated life-time testing will be presented

The Mechanical and Microstructural Changes of Sn-Ag-Bi Solders with Cooling Rate and Bi Content Variations

NASA Astrophysics Data System (ADS)

Abd El-Rehim, A. F.; Zahran, H. Y.; AlFaify, S.

2018-02-01

The purpose of this study is to investigate the influence of cooling rate and Bi addition on the microstructure evolution and mechanical properties of Sn-3.5Ag alloy. A series of Sn-3.5Ag-xBi solders has been fabricated with Bi content in the range of 0.5-3.5 wt.%. After solution heat treatment at 170 °C for 24 h and subsequent aging heat treatment at 100 °C for 2 h, samples were divided into two groups. One group was rapidly quenched into iced water (water quenching) for the fast cooling rate (20 °C/s), while the second group was slowly cooled (furnace cooling) in the furnace for the slow cooling rate (0.2 °C/s) after the furnace reflow. The microstructural evolutions of the present solders have been investigated using x-ray diffraction and scanning electron microscopy. The microhardness was measured to correlate the mechanical properties to alloy compositions and cooling rate. It was found that the microhardness of Sn-3.5Ag-xBi solders increased with increasing cooling rate. The indentation creep curves have been evaluated from the obtained microhardness values. Results revealed the steady-state creep rate decreased with increasing Bi content exhibiting an anomalous behavior at 2.5Bi. The reason for improved creep resistance of Sn-3.5Ag-xBi solders is the result of the combination of the solid solution strengthening and precipitation strengthening of Bi. The mean values of stress exponent indicated that the operative creep mechanism is dislocation climb.

Method of fabricating a solar cell array

DOEpatents

Lazzery, Angelo G.; Crouthamel, Marvin S.; Coyle, Peter J.

1982-01-01

A first set of pre-tabbed solar cells are assembled in a predetermined array with at least part of each tab facing upward, each tab being fixed to a bonding pad on one cell and abutting a bonding pad on an adjacent cell. The cells are held in place with a first vacuum support. The array is then inverted onto a second vacuum support which holds the tabs firmly against the cell pads they abut. The cells are exposed to radiation to melt and reflow the solder pads for bonding the tab portions not already fixed to bonding pads to these pads.

Growth Behavior of Intermetallic Compounds at SnAgCu/Ni and Cu Interfaces

NASA Astrophysics Data System (ADS)

Qi, Lihua; Huang, Jihua; Zhang, Hua; Zhao, Xingke; Wang, Haitao; Cheng, Donghai

2010-02-01

The growth behavior of reaction-formed intermetallic compounds (IMCs) at Sn3.5Ag0.5Cu/Ni and Cu interfaces under thermal-shear cycling conditions was investigated. The results show that the morphology of (Cu x Ni1- x )6Sn5 and Cu6Sn5 IMCs formed both at Sn3.5Ag0.5Cu/Ni and Cu interfaces gradually changed from scallop-like to chunk-like, and different IMC thicknesses developed with increasing thermal-shear cycling time. Furthermore, Cu6Sn5 IMC growth rate at the Sn3.5Ag0.5Cu/Cu interface was higher than that of (Cu x Ni1- x )6Sn5 IMC under thermal-shear cycling. Compared to isothermal aging, thermal-shear cycling led to only one Cu6Sn5 layer at the interface between SnAgCu solder and Cu substrate after 720 cycles. Moreover, Ag3Sn IMC was dispersed uniformly in the solder after reflow. The planar Ag3Sn formed near the interface changed remarkably and merged together to large platelets with increasing cycles. The mechanism of formation of Cu6Sn5, (Cu x Ni1- x )6Sn5 and Ag3Sn IMCs during thermal-shear cycling process was investigated.

Interconnection of thermal parameters, microstructure and mechanical properties in directionally solidified Sn–Sb lead-free solder alloys

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dias, Marcelino; Costa, Thiago; Rocha, Otávio

2015-08-15

Considerable effort is being made to develop lead-free solders for assembling in environmental-conscious electronics, due to the inherent toxicity of Pb. The search for substitute alloys of Pb–Sn solders has increased in order to comply with different soldering purposes. The solder must not only meet the expected levels of electrical performance but may also have appropriate mechanical strength, with the absence of cracks in the solder joints. The Sn–Sb alloy system has a range of compositions that can be potentially included in the class of high temperature solders. This study aims to establish interrelations of solidification thermal parameters, microstructure andmore » mechanical properties of Sn–Sb alloys (2 wt.%Sb and 5.5 wt.%Sb) samples, which were directionally solidified under cooling rates similar to those of reflow procedures in industrial practice. A complete high-cooling rate cellular growth is shown to be associated with the Sn–2.0 wt.%Sb alloy and a reverse dendrite-to-cell transition is observed for the Sn–5.5 wt.%Sb alloy. Strength and ductility of the Sn–2.0 wt.%Sb alloy are shown not to be affected by the cellular spacing. On the other hand, a considerable variation in these properties is associated with the cellular region of the Sn–5.5 wt.%Sb alloy casting. - Graphical abstract: Display Omitted - Highlights: • The microstructure of the Sn–2 wt.%Sb alloy is characterized by high-cooling rates cells. • Reverse dendrite > cell transition occurs for Sn–5.5 wt.%Sb alloy: cells prevail for cooling rates > 1.2 K/s. • Sn–5.5 wt.%Sb alloy: the dendritic region occurs for cooling rates < 0.9 K/s. • Sn–5.5 wt.%Sb alloy: tensile properties are improved with decreasing cellular spacing.« less

Effects of Sn Layer Orientation on the Evolution of Cu/Sn Interfaces

NASA Astrophysics Data System (ADS)

Sun, Menglong; Zhao, Zhangjian; Hu, Fengtian; Hu, Anmin; Li, Ming; Ling, Huiqin; Hang, Tao

2018-03-01

The effects of Sn layer orientation on the evolution of Cu/Sn joint interfaces were investigated. Three Sn layers possessing (112), (321) and (420) orientations were electroplated on polycrystalline Cu substrates respectively. The orientations of Sn layer preserved during reflowing at 250 °C for 10 s. After aging at 150 °C for different time, the interfacial microstructures were observed from the cross-section and top-view. The alignment between the c-axis of Sn and Cu diffusion direction significantly sped up the Cu diffusion, leading to the thickest intermetallic compound layer formed in (112) joint. Two types of voids, namely, intracrystalline voids and grain islanding caused intercrystalline voids generated at Cu/Cu3Sn interfaces due to the different interdiffusion coefficients of Cu and Sn (112) oriented Sn/Cu joint produced many more voids than (321) joint, and no voids were detected in (420) joint. Therefore, to enhance the reliability of solder joints, using (420) oriented Sn as solder layer could be an efficient way.

Investigation of electromigration behavior in lead-free flip chip solder bumps

NASA Astrophysics Data System (ADS)

Kalkundri, Kaustubh Jayant

Packaging technology has also evolved over time in an effort to keep pace with the demanding requirements. Wirebond and flip chip packaging technologies have become extremely versatile and ubiquitous in catering to myriad applications due to their inherent potential. This research is restricted strictly to flip chip technology. This technology incorporates a process in which the bare chip is turned upside down, i.e., active face down, and is bonded through the I/O to the substrate, hence called flip chip. A solder interconnect that provides electrical connection between the chip and substrate is bumped on a processed silicon wafer prior to dicing for die-attach. The assembly is then reflow-soldered followed by the underfill process to provide the required encapsulation. The demand for smaller and lighter products has increased the number of I/Os without increasing the package sizes, thereby drastically reducing the size of the flip chip solder bumps and their pitch. Reliability assessment and verification of these devices has gained tremendous importance due to their shrinking size. To add to the complexity, changing material sets that are results of recently enacted lead-free solder legislations have raised some compatibility issues that are already being researched. In addition to materials and process related flip chip challenges such as solder-flux compatibility, Coefficient of Thermal Expansion (CTE) mismatch, underfill-flux compatibility and thermal management, flip chip packages are vulnerable to a comparatively newer challenge, namely electromigration observed in solder bumps. It is interesting to note that electromigration has come to the forefront of challenges only recently. It has been exacerbated by the reduction in bump cross-section due to the seemingly continuous shrinking in package size over time. The focus of this research was to understand the overall electromigration behavior in lead-free (SnAg) flip chip solder bumps. The objectives of the research were to comprehend the physics of failure mechanism in electromigration for lead-free solder bumps assembled in a flip chip ceramic package having thick copper under bump metallization and to estimate the unknown critical material parameters from Black's equation that describe failure due to electromigration. In addition, the intent was to verify the 'use condition reliability' by extrapolation from experimental conditions. The methodology adopted for this research was comprised of accelerated electromigration tests on SnAg flip chip solder bumps assembled on ceramic substrate with a thick copper under bump metallization. The experimental approach was comprised of elaborate measurement of the temperature of each sample by separate metallization resistance exhibiting positive resistance characteristics to overcome the variation in Joule heating. After conducting the constant current experiments and analyzing the failed samples, it was found that the primary electromigration failure mode observed was the dissolution of the thick copper under bump metallization in the solder, leading to a change in resistance. The lifetime data obtained from different experiments was solved simultaneously using a multiple regression approach to yield the unknown Black's equation parameters of current density exponent and activation energy. In addition to the implementation of a systematic failure analysis and data analysis procedure, it was also deduced that thermomigration due to the temperature gradient across the chip does impact the overall electromigration behavior. This research and the obtained results were significant in bridging the gap for an overall understanding of this critical failure mode observed in flip chip solder bumps. The measurement of each individual sample temperature instead of an average temperature enabled an accurate analysis for predicting the 'use condition reliability' of a comparable product. The obtained results and the conclusions can be used as potential inputs in future designs and newer generations of flip chip devices that might undergo aggressive scaling. This will enable these devices to retain their functionality during their intended useful life with minimal threat of failure due to the potent issue of electromigration. (Abstract shortened by UMI.)

Experimental investigation on sandwich structure ring-type ultrasonic motor.

PubMed

Peng, Taijiang; Shi, Hongyan; Liang, Xiong; Luo, Feng; Wu, Xiaoyu

2015-02-01

This paper presents a manufacture method for a sandwich structure Ultrasonic Motor (USM) and experiment. Two pieces of rotor clamped on a stator, and a stainless steel disk-spring is bonded on the hollow rotor disk to provide the press by a nut assembled on the shaft. The stator is made of a double-side Printed-Circuit Board (PCB) which is sawed out the ring in the center and connected on the board with three legs. On each side of the ring surface, there are electrodes connected at the same position via through hole. The three layer drive circuit for sine, cosine, and ground signal is connected on the board through each leg. There are many piezoelectric components (PZT) bonded between two electrodes and fill soldering tin on each electrode. Then PZT is welded on PCB by reflow soldering. Finally, rub the gibbous soldering tin down to the position of PZT surface makes sure the surface contacts with rotor evenly. The welding process can also be completed by Surface Mounted Technology (SMT). A prototype motor is manufactured by this method. Two B03 model shapes of the stator are obtained by the finite element analysis and the optimal frequency of the motor is 56.375 kHz measured by impedance instrument. The theoretical analysis is conducted for the relationship between the revolving speed of the USM and thickness of stator ring, number of the travelling waves, PZT amplitude, frequency and the other parameters. The experiment result shows that the maximum revolving speed is 116 RPM and the maximum torque is 25 N mm, when the actuate voltage is 200 VAC. Copyright © 2014 Elsevier B.V. All rights reserved.

Impact of Reflow on the Output Characteristics of Piezoelectric Microelectromechanical System Devices

NASA Astrophysics Data System (ADS)

Nogami, Hirofumi; Kobayashi, Takeshi; Okada, Hironao; Masuda, Takashi; Maeda, Ryutaro; Itoh, Toshihiro

2012-09-01

An animal health monitoring system and a wireless sensor node aimed at preventing the spread of animal-transmitted diseases and improving pastoral efficiency which are especially suitable for chickens, were developed. The sensor node uses a piezoelectric microelectromechanical system (MEMS) device and an event-driven system that is activated by the movements of a chicken. The piezoelectric MEMS device has two functions: a) it measures the activity of a chicken and b) switches the micro-control unit (MCU) of the wireless sensor node from the sleep mode. The piezoelectric MEMS device is required to produce high output voltages when the chicken moves. However, after the piezoelectric MEMS device was reflowed to the wireless sensor node, the output voltages of the piezoelectric MEMS device decreased. The main reason for this might be the loss of residual polarization, which is affected by the thermal load during the reflow process. After the reflow process, we were not able to apply a voltage to the piezoelectric MEMS device; thus, the piezoelectric output voltage was not increased by repoling the piezoelectric MEMS device. To address the thermal load of the reflow process, we established a thermal poling treatment, which achieves a higher temperature than the reflow process. We found that on increasing the thermal poling temperature, the piezoelectric output voltages did not decreased low significantly. Thus, we considered that a thermal poling temperature higher than that of the reflow process prevents the piezoelectric output voltage reduction caused by the thermal load.

Fabrication of high quality aspheric microlens array by dose-modulated lithography and surface thermal reflow

NASA Astrophysics Data System (ADS)

Huang, Shengzhou; Li, Mujun; Shen, Lianguan; Qiu, Jinfeng; Zhou, Youquan

2018-03-01

A novel fabrication method for high quality aspheric microlens array (MLA) was developed by combining the dose-modulated DMD-based lithography and surface thermal reflow process. In this method, the complex shape of aspheric microlens is pre-modeled via dose modulation in a digital micromirror device (DMD) based maskless projection lithography. And the dose modulation mainly depends on the distribution of exposure dose of photoresist. Then the pre-shaped aspheric microlens is polished by a following non-contact thermal reflow (NCTR) process. Different from the normal process, the reflow process here is investigated to improve the surface quality while keeping the pre-modeled shape unchanged, and thus will avoid the difficulties in generating the aspheric surface during reflow. Fabrication of a designed aspheric MLA with this method was demonstrated in experiments. Results showed that the obtained aspheric MLA was good in both shape accuracy and surface quality. The presented method may be a promising approach in rapidly fabricating high quality aspheric microlens with complex surface.

High Bismuth Alloys as Lead-Free Alternatives for Interconnects in High-Temperature Electronics

NASA Astrophysics Data System (ADS)

Mallampati, Sandeep

Predominant high melting point solders for high-temperature electronics (operating temperatures from 200 to 250°C) are Pb-based which are being banned from usage due to their toxic nature. In this study, high bismuth alloy compositions (Bi-14Cu-8Sn, Bi-20Sb-10Cu, Bi-15Sb-10Cu and Bi-10Sb-10Cu) were designed, cast, and characterized to understand their potential as replacements. The desirable aspect of Bi is its high melting temperature, which is 271°C. Alloying elements Sn, Sb and Cu were added to improve some of its properties such as thermal conductivity, plasticity, and reactivity with Cu and Ni surface. Metallographic sectioning and microstructure analysis were performed on the bulk alloys to compare the evolution of phases predicted from equilibrium phase diagrams. Reflow processes were developed to make die-attach samples out of the proposed alloys and die-shear testing was carried out to characterize mechanical integrity of the joint. Thermal shock between -55°C to 200°C and high temperature storage at 200°C were performed on the assembled die-attach samples to study microstructure evolution and mechanical behavior of the reflowed alloys under accelerated testing conditions. In addition, heat dissipation capabilities, using flash diffusivity, were measured on the bulk alloys and also on the die-attach assembly. Finally, tensile testing was performed on the dogbone specimens to identify the potential for plastic deformation and electron backscatter diffraction (EBSD) analysis was used to study the grain orientations on the fracture surfaces and their influence on the crack propagation. Bi-14Cu-8Sn has formed BiNi by on the die backside metallization and the reaction with Cu was poor. This has resulted in weaker substrate side interface. It was observed that Bi-Sb alloys have strong reactivity with Ni (forming Bi3Ni, BiNi and NiSb intermetallic phases), and with Cu (forming Cu2Sb, Cu4Sb). Spallation was observed in NiSb interfacial intermetallic layer and the reflow process was optimized to minimize spallation. Die-attach joints made out of Bi-15Sb-10Cu alloy, with the improved reflow process, have shown an average shear strength of 24 MPa with low standard deviation, which is comparable to that of commercially available high Pb solders. Bi-15Sb-10Cu alloy has shown limited plastic deformation in room temperature testing. The fracture propagated through the (111) cleavage planes of rhombohedral crystal structure of the Bi(Sb) matrix. The same alloy has shown up to 7% plastic strain under tension when tested at 175°C. The cleavage planes, which were oriented at higher angles to the tensile axis, contributed to plasticity in the high temperature test. The thermal conductivity of all the alloys was higher than that of pure Bi. Cu2Sb precipitates form high conductive paths in a matrix that has relatively lower conductivity, thereby enhancing thermal conductivity of the Bi alloys. By creating high volume fraction of precipitates in a die-attach joint microstructure, it was feasible to further increase the thermal conductivity of this joint to 24 W/m˙K, which is three times higher than that of pure Bi (8 W/m˙K). Delamination along the die side interfacial NiSb layer was the most commonly observed failure mode in thermal shock tests. The die-attach samples made with Bi-15Sb-10Cu, however, retained the original shear strength even after thermal shock and high temperature storage. The microstructures of these samples revealed formation of Bi3Ni on the die side interface that prevented it from being delaminated. Bi-15Sb-10Cu alloy has so far shown the most promising performance as a die-attach material for high temperature applications (operated over 200°C).

Reflow-oven-processing of pressureless sintered-silver interconnects

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wereszczak, Andrew A.; Chen, Branndon R.; Oistad, Brian A.

Here, a method was developed to pressurelessly fabricate strong and consistent sinterable-silver joints or interconnects using reflow oven heating. Circular sinterable-silver interconnects, having nominal diameter of 5 mm and 0.1 mm thickness were stencil printed, contact-dried, and then pressurelessly sinter-bonded to Au-plated direct copper bonded ceramic substrates at 250 °C in ambient air. That sintering was done in either a reflow oven or a convective oven (latter being a conventional heating source for processing sinterable-silver). Consistently strong (>40 MPa) interconnects were produced with reflow oven heating and were as strong as those produced with convective oven heating. This is significantmore » because reflow oven technology affords better potential for continuous mass production and it was shown that strong sintered-silver bonds can indeed be achieved with its use.« less

Reflow-oven-processing of pressureless sintered-silver interconnects

DOE PAGES

Wereszczak, Andrew A.; Chen, Branndon R.; Oistad, Brian A.

2018-01-04

Here, a method was developed to pressurelessly fabricate strong and consistent sinterable-silver joints or interconnects using reflow oven heating. Circular sinterable-silver interconnects, having nominal diameter of 5 mm and 0.1 mm thickness were stencil printed, contact-dried, and then pressurelessly sinter-bonded to Au-plated direct copper bonded ceramic substrates at 250 °C in ambient air. That sintering was done in either a reflow oven or a convective oven (latter being a conventional heating source for processing sinterable-silver). Consistently strong (>40 MPa) interconnects were produced with reflow oven heating and were as strong as those produced with convective oven heating. This is significantmore » because reflow oven technology affords better potential for continuous mass production and it was shown that strong sintered-silver bonds can indeed be achieved with its use.« less

Hybrid integration of VCSELs onto a silicon photonic platform for biosensing application

NASA Astrophysics Data System (ADS)

Lu, Huihui; Lee, Jun Su; Zhao, Yan; Cardile, Paolo; Daly, Aidan; Carroll, Lee; O'Brien, Peter

2017-02-01

This paper presents a technology of hybrid integration vertical cavity surface emitting lasers (VCSELs) directly on silicon photonics chip. By controlling the reflow of the solder balls used for electrical and mechanical bonding, the VCSELs were bonded at 10 degree to achieve the optimum angle-of-incidence to the planar grating coupler through vision based flip-chip techniques. The 1 dB discrepancy between optical loss values of flip-chip passive assembly and active alignment confirmed that the general purpose of the flip-chip design concept is achieved. This hybrid approach of integrating a miniaturized light source on chip opens the possibly of highly compact sensor system, which enable future portable and wearable diagnostics devices.

Lubricant reflow after laser heating in heat assisted magnetic recording

NASA Astrophysics Data System (ADS)

Wu, Haoyu; Mendez, Alejandro Rodriguez; Xiong, Shaomin; Bogy, David B.

2015-05-01

In heat assisted magnetic recording (HAMR) technology for hard disk drives, the media will be heated to about 500 °C during the writing process in order to reduce its magnetic coercivity and thus allow data writing with the magnetic head transducers. The traditional lubricants such as Z-dol and Z-tetraol may not be able to perform in such harsh heating conditions due to evaporation, decomposition and thermal depletion. However, some of the lubricant depletion can be recovered due to reflow after a period of time, which can help to reduce the chance of head disk interface failure. In this study, experiments of lubricant thermal depletion and reflow were performed using a HAMR test stage for a Z-tetraol type lubricant. Various lubricant depletion profiles were generated using different laser heating conditions. The lubricant reflow process after thermal depletion was monitored by use of an optical surface analyzer. In addition, a continuum based lubrication model was developed to simulate the lubricant reflow process. Reasonably good agreement between simulations and experiments was achieved.

Development and fabrication of a high current, fast recovery power diode

NASA Technical Reports Server (NTRS)

Berman, A. H.; Balodis, V.; Devance, D. C.; Gaugh, C. E.; Karlsson, E. A.

1983-01-01

A high voltage (VR = 1200 V), high current (IF = 150 A), fast recovery ( 700 ns) and low forward voltage drop ( 1.5 V) silicon rectifier was designed and the process developed for its fabrication. For maximum purity, uniformity and material characteristic stability, neutron transmutation n-type doped float zone silicon is used. The design features a hexagonal chip for maximum area utilization of space available in the DO-8 diode package, PIN diffused junction structure with deep diffused D(+) anode and a shallow high concentration n(+) cathode. With the high temperature glass passivated positive bevel mesa junction termination, the achieved blocking voltage is close to the theoretical limit of the starting material. Gold diffusion is used to control the lifetime and the resulting effect on switching speed and forward voltage tradeoff. For solder reflow assembly, trimetal (Al-Ti-Ni) contacts are used. The required major device electrical characteristics were achieved. Due to the tradeoff nature of forward voltage drop and reverse recovery time, a compromise was reached for these values.

Integrated Electrode Arrays for Neuro-Prosthetic Implants

NASA Technical Reports Server (NTRS)

Brandon, Erik; Mojarradi, Mohammede

2003-01-01

Arrays of electrodes integrated with chip-scale packages and silicon-based integrated circuits have been proposed for use as medical electronic implants, including neuro-prosthetic devices that might be implanted in brains of patients who suffer from strokes, spinal-cord injuries, or amyotrophic lateral sclerosis. The electrodes of such a device would pick up signals from neurons in the cerebral cortex, and the integrated circuit would perform acquisition and preprocessing of signal data. The output of the integrated circuit could be used to generate, for example, commands for a robotic arm. Electrode arrays capable of acquiring electrical signals from neurons already exist, but heretofore, there has been no convenient means to integrate these arrays with integrated-circuit chips. Such integration is needed in order to eliminate the need for the extensive cabling now used to pass neural signals to data-acquisition and -processing equipment outside the body. The proposed integration would enable progress toward neuro-prostheses that would be less restrictive of patients mobility. An array of electrodes would comprise a set of thin wires of suitable length and composition protruding from and supported by a fine-pitch micro-ball grid array or chip-scale package (see figure). The associated integrated circuit would be mounted on the package face opposite the probe face, using the solder bumps (the balls of the ball grid array) to make the electrical connections between the probes and the input terminals of the integrated circuit. The key innovation is the insertion of probe wires of the appropriate length and material into the solder bumps through a reflow process, thereby fixing the probes in place and electrically connecting them with the integrated circuit. The probes could be tailored to any distribution of lengths and made of any suitable metal that could be drawn into fine wires. Furthermore, the wires could be coated with an insulating layer using anodization or other processes, to achieve the correct electrical impedance. The probe wires and the packaging materials must be biocompatible using such materials as lead-free solders. For protection, the chip and package can be coated with parylene.

Relationship between morphologies and orientations of Cu{sub 6}Sn{sub 5} grains in Sn3.0Ag0.5Cu solder joints on different Cu pads

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tian, Yanhong, E-mail: tianyh@hit.edu.cn; Zhang, Rui; Hang, Chunjin

2014-02-15

The morphologies and orientations of Cu{sub 6}Sn{sub 5} intermetallic compounds in the Sn3.0Ag0.5Cu solder joints both on polycrystalline and single crystal Cu pads under different peak reflow temperatures and times above liquids were investigated. The relationship between Cu{sub 6}Sn{sub 5} grain orientations and morphologies was clarified. At the interface of Sn3.0Ag0.5Cu/polycrystalline Cu pad, scalloped Cu{sub 6}Sn{sub 5} intermetallic compounds formed at 250 °C and roof shape Cu{sub 6}Sn{sub 5} formed at 300 °C. Both scalloped Cu{sub 6}Sn{sub 5} and roof shape Cu{sub 6}Sn{sub 5} had a preferred orientation of (0001) plane being parallel to polycrystalline Cu pad surface. Besides, themore » percentage of large angle grain boundaries increased as the peak reflow temperature rose. At the interface of Sn3.0Ag0.5Cu/(111) single crystal Cu pad, the Cu{sub 6}Sn{sub 5} intermetallic compounds were mainly scallop-type at 250 °C and were prism type at 300 °C. The prismatic Cu{sub 6}Sn{sub 5} grains grew along the three preferred directions with the inter-angles of 60° on (111) single crystal Cu pad while along two perpendicular directions on (100) single crystal Cu pad. The orientation relationship between Cu{sub 6}Sn{sub 5} grains and the single crystal Cu pads was investigated by electron backscatter diffraction technology. In addition, two types of hollowed Cu{sub 6}Sn{sub 5} intermetallic compounds were found inside the joints of polycrystalline Cu pads. The long hexagonal Cu{sub 6}Sn{sub 5} strips were observed in the joints reflowing at 250 °C while the hollowed Cu{sub 6}Sn{sub 5} strips with the ‘▪’ shape cross-sections appeared at 300 °C, which was attributed to the different grain growth rates of different Cu{sub 6}Sn{sub 5} crystal faces. - Highlights: • The orientation of interfacial Cu{sub 6}Sn{sub 5} grains was obtained by EBSD technology. • Two types of hollowed Cu{sub 6}Sn{sub 5} strips were found at different temperatures. • The formation mechanism of hollowed Cu{sub 6}Sn{sub 5} was elaborated based on Bravais law. • The relationship between Cu{sub 6}Sn{sub 5} grain orientations and morphologies was clarified.« less

Low-profile fiber connector for co-packaged optics

NASA Astrophysics Data System (ADS)

Brusberg, Lars; DeJong, Michael; Butler, Douglas L.; Clark, Jeffrey S.; Sutton, Clifford G.

2018-02-01

We developed a small form factor connector that can be assembled on all four sides of a high-data switch package for fiber connectivity. This paper discusses a novel connector approach that has the potential to meet all co-packaging requirements including solder-reflow-compatibility, de-mateability, low insertion loss and state-of-the art FAU attach. The connector was attached to the PIC for performance evaluation. The average insertion loss across all eight fibers of the assembly was 1.77 dB, including the three optical interfaces: (1) MT-to-MT between connector and receptacle, (2) receptacle-to-PLC and (3) PIC-to-FAU. Also included is the propagation loss of the PIC waveguide. Optical return loss was measured to be -55 dB or lower.

Flexible fabrication of biomimetic compound eye array via two-step thermal reflow of simply pre-modeled hierarchic microstructures

NASA Astrophysics Data System (ADS)

Huang, Shengzhou; Li, Mujun; Shen, Lianguan; Qiu, Jinfeng; Zhou, Youquan

2017-06-01

A flexible fabrication method for the biomimetic compound eye (BCE) array is proposed. In this method, a triple-layer sandwich-like coating configuration was introduced, and the required hierarchic microstructures are formed with a simple single-scan exposure in maskless digital lithography. Taking advantage of the difference of glass transition point (Tg) between photoresists of each layer, the pre-formed hierarchic microstructures are in turn reflowed to the curved substrate and the BCE ommatidia in a two-step thermal reflow process. To avoid affecting the spherical substrate formed in the first thermal reflow, a non-contact strategy was proposed in the second reflow process. The measurement results were in good agreement with the designed BCE profiles. Results also showed that the fabricated BCE had good performances in optical test. The presented method is flexible, convenient, low-cost and can easily adapt to the fabrications of other optical elements with hierarchic microstructures.

Characterization and modeling of microstructural evolution of near-eutectic tin-silver-copper solder joints

NASA Astrophysics Data System (ADS)

Zbrzezny, Adam R.

Near-eutectic Sn-Ag-Cu (SAC) solders are currently considered as major lead-free replacement candidates for Sn-Pb eutectic alloys in microelectronics applications. In this thesis, the microstructural thermal stability including recrystallization, grain growth behavior, Pb and Au contamination effects and interaction of the SAC solder with Cu and Ni substrates were investigated. The true eutectic composition of the Sn-Ag-Cu alloy was verified to be Sn3.5Ag0.9Cu wt.%, and the eutectic melting temperature was determined to be 217.4 +/- 0.8°C. The system was classified as belonging to faceting (Cu6Sn5)-faceting (Ag3Sn)-nonfaceting (Sn matrix) ternary eutectic. The most significant consequence of Pb contamination was the formation of a quaternary eutectic phase (Sn-Ag-Cu-Pb) with a melting point at 176°C. Similarly, the presence of gold in the SAC alloy led to a development of a new quaternary phase (Sn-Ag-Cu-Au) melting at 204°C. Prolonged aging of SAC-4 wt.% Au on nickel resulted in the deposition of a new, previously unreported, intermetallic (IMC) layer, ((Au1-xCUx)6Sn 5, 15 wt.% of Au) on top of the existing (Cu1-yNi y)6Sn5 layer. The interfacial products that formed during soldering to copper were Cu6Sn5 and Cu3Sn. Soldering to nickel resulted in the formation of one layer, (Cu1-yNiy) 6Sn5, which was different from the expected Ni3Sn 4 layer. A small copper content in the SAC solder (0.7 wt.%) was sufficient to promote this thermodynamic shift. Intermetallic growth on Cu during solid state aging was established to be bulk diffusion controlled. The IMC layers in the SAC system grew at a slower rate than in the Sn-Pb system. It was found that the reliability of SAC solder joints on copper was considerably better than on nickel due to copper enrichment during reflow and subsequent Cu6Sn5 intermetallic precipitation. Enhanced copper and silver diffusion followed by tin recrystallization and grain growth, cavity nucleation and subsequent micro-crack linkage formed the framework of a proposed microstructural model of solder degradation mechanisms under cyclic creep conditions. A multilayer diffusion model of the SAC/Cu couple was proposed and employed for predicting intermetallic layer growth kinetics. In general, the calculated IMC thicknesses for short and intermediate aging times were in reasonable agreement with the experimental data.

Mechanical Properties and Microstructure Investigation of Lead Free Solder

NASA Technical Reports Server (NTRS)

Wang, Qing; Gail, William F.; Johnson, R. Wayne; Strickland, Mark; Blanche, Jim

2005-01-01

While the electronics industry appears to be focusing on Sn-Ag-Cu as the alloy of choice for lead free electronics assembly, ,the exact composition varies by geographic region, supplier and user. Add to that dissolved copper and silver from the printed circuit board traces and surface finish, and there can be significant variation in the final solder joint composition. A systematic study of the mechanical and microstructural properties of Sn-Ag-Cu alloys with Ag varying from 2wt% to 4wt% and Cu varying from 0.5wt% to lSwt%, was undertaken in this research study. Different sample preparation techniques (water quenched, oil quenched and water quenched followed by reflow) were explored and the resulting microstructure compared to that of a typical reflowed lead free chip scale package (CSP) solder joint. Tensile properties (modulus, 0.2% yield strength and the ultimate tensile strength) and creep behavior of selected alloy compositions (Sn-4Ag-1 X u , Sn-4Ag-OSCu, Sn- 2Ag-1 X u , Sn-2Ag-OSCu, Sn-3.5Ag-O.SCu) were determined for three conditions: as- cast; aged for 100 hours at 125OC; and aged for 250 hours at 125OC. There was no significant difference in Young's Modulus as a function of alloy composition. After an initial decrease in modulus after 100 hours at 125"C, there was an insignificant change with further aging. The distribution of 0.2% strain yield stress and ultimate tensile strength as a function of alloy composition was more significant and decreased with aging time and temperature. The microstructures of these alloys were examined using light and scanning electron microscopy (LM and SEM) respectively and SEM based energy dispersive x-ray spectroscopy (EDS). Fracture surface and cross-section analysis were performed on the specimens after creep testing. The creep testing results and the effect of high temperature aging on mechanical properties is presented for the oil quenched samples. In general the microstructure of oil quenched specimen exhibited a eutectic region of Sn with moderately dispersed Ag3Sn intermetallic, surrounded by a dendritic Sn-rich phase. The SEM images of the fracture surface indicated the presence of a tough shear surface at the initial cavity break area and a break line in the middle of specimen along the failure direction. A hyperbolic-sine creep model was adopted and used to fit the creep experiment data. The effect on the mechanical properties by adding the quaternary element bismuth to the Sn-3.5Ag-0.8Cu alloy was measured and compared with the mechanical properties of the ternary alloys. The results of this research study provide necessary data for the modeling of solder joint reliability for a range of Sn-Ag-Cu compositions and a baseline for evaluating the effects of subsequent quaternary additions.

Reflow dynamics of thin patterned viscous films

NASA Astrophysics Data System (ADS)

Leveder, T.; Landis, S.; Davoust, L.

2008-01-01

This letter presents a study of viscous smoothening dynamics of a nanopatterned thin film. Ultrathin film manufacturing processes appearing to be a key point of nanotechnology engineering and numerous studies have been recently led in order to exhibit driving parameters of this transient surface motion, focusing on time scale accuracy method. Based on nanomechanical analysis, this letter shows that controlled shape measurements provided much more detailed information about reflow mechanism. Control of reflow process of any complex surface shape, or measurement of material parameter as thin film viscosity, free surface energy, or even Hamaker constant are therefore possible.

Flip-chip integration of tilted VCSELs onto a silicon photonic integrated circuit.

PubMed

Lu, Huihui; Lee, Jun Su; Zhao, Yan; Scarcella, Carmelo; Cardile, Paolo; Daly, Aidan; Ortsiefer, Markus; Carroll, Lee; O'Brien, Peter

2016-07-25

In this article we describe a cost-effective approach for hybrid laser integration, in which vertical cavity surface emitting lasers (VCSELs) are passively-aligned and flip-chip bonded to a Si photonic integrated circuit (PIC), with a tilt-angle optimized for optical-insertion into standard grating-couplers. A tilt-angle of 10° is achieved by controlling the reflow of the solder ball deposition used for the electrical-contacting and mechanical-bonding of the VCSEL to the PIC. After flip-chip integration, the VCSEL-to-PIC insertion loss is -11.8 dB, indicating an excess coupling penalty of -5.9 dB, compared to Fibre-to-PIC coupling. Finite difference time domain simulations indicate that the penalty arises from the relatively poor match between the VCSEL mode and the grating-coupler.

Modified Process Reduces Porosity when Soldering in Reduced Gravity Environments

NASA Technical Reports Server (NTRS)

Watson, Kevin; Struk, Peter; Pettegrew, Richard; Downs, Robert; Haylett, Daniel

2012-01-01

A modified process yields lower levels of internal porosity for solder joints produced in reduced-gravity environments. The process incorporates both alternative materials and a modified procedure. The process provides the necessary cleaning action to enable effective bonding of the applied solder alloy with the materials to be joined. The modified process incorporates a commercially available liquid flux that is applied to the solder joint before heating with the soldering iron. It is subsequently heated with the soldering iron to activate the cleaning action of the flux and to evaporate most of the flux, followed by application of solder alloy in the form of commercially available solid solder wire (containing no flux). Continued heating ensures adequate flow of the solder alloy around and onto the materials to be joined. The final step is withdrawal of the soldering iron to allow alloy solidification and cooling of the solder joint.

Understanding the reliability of solder joints used in advanced structural and electronics applications: Part 1 - Filler metal properties and the soldering process

DOE PAGES

Vianco, Paul T.

2017-02-01

Soldering technology has made tremendous strides in the past half-century. Whether structural or electronic, all solder joints must provide a level of reliability that is required by the application. This Part 1 report examines the effects of filler metal properties and soldering process on joint reliability. Solder alloy composition must have the appropriate melting and mechanical properties that suit the product's assembly process(es) and use environment. The filler metal must also optimize solderability (wetting-and-spreading) to realize the proper joint geometry. Here, the soldering process also affects joint reliability. The choice of flux and thermal profile support the solderability performance ofmore » the molten filler metal to successfully fill the gap and complete the fillet.« less

Pb-free electronics: from nanotechnology to combinatorial materials science

NASA Astrophysics Data System (ADS)

Diaz Gonzalez, Alfredo J.

The elimination of lead (Pb) from the electronics industry due to a government directive caused problems on the manufacturing and use of electronic components. The current alloys used to attach components have a significant higher processing temperature (~30-40°C) that those containing Pb. The higher processing temperatures cause damage to the electronic components; printed circuit boards (PCB) and represents an increase in energetic costs for the manufacurer. Tin whiskers are out-of-plane structures that grow from tin (Sn) plated surfaces and cause short circuits and metal vapor arc. The electrical connection of components to the PCB relies on leads that are close to each other and are manufactured from tin-plated copper. Materials have shown a tendency to modify their bulk properties depending on powder particle size. Nanoparticle's coalescence temperature tends to decrease as particle size decreases. Exploiting this behavior, a nanoparticle based solder paste has been developed for attaching electronic components at a lower processing temperature to avoid thermally induced damage and reduce energy consumption. Tin nanoparticles were successfully synthesized via a wet chemistry route using tin (II) chloride dihydrated (metal precursor), 1,10-Phenanthroline (surfactant), and sodium borohydride (reducing agent). A flux system was developed based on Ethylene Glycol. Results showed acceptable coalescence of the non-capped nanoparticles at temperatures as low as 200°C with a processing time of 20 minutes. Synthesized nanoparticles with capping agent required higher flux content thus resulting in a poor metallic load paste. A reduction in processing temperature of approximately 40°C have been found when comparing the developed solder paste with typical SAC lead-free solders (~240°C). The electrical behavior was found to be an order of magnitude below that of bulk tin. Compositional libraries have been developed in an attempt to screen, via a high through-put method, alloys that are prone to tin whiskers growth. These libraries are samples containing a range of sub-samples with varying compositions within it than can be processed simultaneously. Using sputtering, a physical vapor deposition technique, a gradient composed of Ag-Cu was deposited over a Sn-plated Cu substrate. After reflow, the growth mechanism of the whiskers was accelerated using the IEC60068-82-2 standard. SEM and EDS analysis was used to charac-terize the growth of the tin whiskers at different elemental compositions. The gradients found across the samples are in accordance with the theoretical geometrical spacing. Tin whiskers were found on control samples, whereas almost all elemental compositions showed mitigation or elimination of the whiskers. This combinatorial material science methodology proved to be an efficient and fast screening method for the plating materials selection process in Pb-free electronics.

Nanowire surface fastener fabrication on flexible substrate.

PubMed

Toku, Yuhki; Uchida, Keita; Morita, Yasuyuki; Ju, Yang

2018-07-27

The market for wearable devices has increased considerably in recent years. In response to this demand, flexible electronic circuit technology has become more important. The conventional bonding technology in electronic assembly depends on high-temperature processes such as reflow soldering, which result in undesired thermal damages and residual stress at a bonding interface. In addition, it exhibits poor compatibility with bendable or stretchable device applications. Therefore, there is an urgent requirement to attach electronic parts on printed circuit boards with good mechanical and electrical properties at room temperature. Nanowire surface fasteners (NSFs) are candidates for resolving these problems. This paper describes the fabrication of an NSF on a flexible substrate, which can be used for room temperature conductive bonding. The template method is used for preparing high-density nanowire arrays. A Cu thin film is layered on the template as the flexible substrate. After etching the template, a Cu NSF is obtained on the Cu film substrate. In addition, the electrical and mechanical properties of the Cu NSF are studied under various fabrication conditions. The Cu NSF exhibits high shear adhesion strength (∼234 N cm -2 ) and low contact resistivity (2.2 × 10 -4 Ω cm 2 ).

Nanowire surface fastener fabrication on flexible substrate

NASA Astrophysics Data System (ADS)

Toku, Yuhki; Uchida, Keita; Morita, Yasuyuki; Ju, Yang

2018-07-01

The market for wearable devices has increased considerably in recent years. In response to this demand, flexible electronic circuit technology has become more important. The conventional bonding technology in electronic assembly depends on high-temperature processes such as reflow soldering, which result in undesired thermal damages and residual stress at a bonding interface. In addition, it exhibits poor compatibility with bendable or stretchable device applications. Therefore, there is an urgent requirement to attach electronic parts on printed circuit boards with good mechanical and electrical properties at room temperature. Nanowire surface fasteners (NSFs) are candidates for resolving these problems. This paper describes the fabrication of an NSF on a flexible substrate, which can be used for room temperature conductive bonding. The template method is used for preparing high-density nanowire arrays. A Cu thin film is layered on the template as the flexible substrate. After etching the template, a Cu NSF is obtained on the Cu film substrate. In addition, the electrical and mechanical properties of the Cu NSF are studied under various fabrication conditions. The Cu NSF exhibits high shear adhesion strength (∼234 N cm‑2) and low contact resistivity (2.2 × 10‑4 Ω cm2).

Design reflowable digital book template

NASA Astrophysics Data System (ADS)

Prasetya, Didik Dwi; Widiyaningtyas, Triyanna; Arifin, M. Zainal; Wahyu Sakti G., I.

2017-09-01

Electronic books (e-books or digital books) increasingly in demand and continue to grow in the form of future books. One of the standard format electronic books that potential is EPUB (electronic publication) published by the International Digital Publishing Forum (IDPF). This digital book has major advantages are able to provide interactive and reflowable content, which are not found in another book format, such as PDF. Reflowable content allows the book can be accessed through a variety of reader device, like desktop and mobile with a fit and comfort view. However, because the generating process of an EPUB digital book is not as easy a PDF, so this format is less popular. Therefore, in order to help overcome the existing problems, this paper develops digital reflowable text book templates to support electronic learning, especially in Indonesia. This template can be used by anyone to produce a standard digital book quickly and easily without requiring additional specialized knowledge.

The present triumphs and future problems with wave soldering

DOE Office of Scientific and Technical Information (OSTI.GOV)

Vianco, P.T.

1993-10-01

Nearly 40 years of experience with wave soldering have resulted in processes that routinely produce several thousand, defect-free solder joints per minute. However, the climate of electronics manufacturing has changed significantly over the past 10 to 15 years. Environmental restrictions as well as the high quality of products made offshore has placed new demands and challenges on the electronics industry, right down to the assembly process. The impact on wave soldering by environmental regulations and a need for more cost-competitive manufacturing processes has become a serious issue in terms of the economical well-being of the industry. In order to obtainmore » a clearer understanding of the situation, however, it is first most appropriate and necessary to examine the technology of wave soldering. Historically, wave soldering was developed as a refinement of the dip and drag soldering processes with the objective of reducing or eliminating many of the associated defects often present in these earlier processes. Wave soldering reduces the area of contact between the circuit board and the solder. This characteristic, coupled with the agitation generated in the solder, allows flux and its volatile by-products to readily escape from under the board, decreasing the number of skips, unfilled holes, and solder joint voids. The reduced contact area also lessens the potential for thermal damage to the circuit board laminate. Control of the wave profile at the exit point of the circuit board lessens the likelihood of icicles and bridges forming on the solder joints; this latitude is not available in the dip soldering process.« less

hsCRP and ET-1 expressions in patients with no-reflow phenomenon after Percutaneous Coronary Intervention.

PubMed

Liu, Min; Liang, Tian; Zhang, Peiying; Zhang, Qing; Lu, Lei; Wang, Zhongliang

2017-01-01

To explore hsCRP and ET-1 expressions in patients with no-reflow phenomenon after percutaneous coronary intervention (PCI). A total of 136 patients with single coronary artery disease receiving PCI were divided into a reflow group and a no-reflow group to compare the level use of ET-1 alone with combined level of ET-1 and hs-CRP in PCI regarding sensitivity, specificity, positive and negative predictive values and accuracy for postoperative no-reflow. The study was conducted between 2014-2016 at our hospital. Postoperative levels of ET-1 and hs-CRP in no-reflow group were significantly higher than those of reflow group (P<0.05). ET-1 level of reflow group peaked three hours after PCI and then declined. Serum level of hs-CRP decreased most obviously within three hours after PCI in reflow group and three hours - three days after PCI in no-reflow group. Left ventricular end-diastolic diameters of both groups after PCI were apparently lower than those before PCI, without significant inter-group difference (P>0.05). Left ventricular end-systolic diameters and left ventricular ejection fractions of both groups evidently increased after PCI, without significant inter-group differences either (P>0.05). Corrected TIMI frame count (CTFC) and wall motion score index of reflow group after PCI were significantly lower than those of no-reflow group (P<0.05). ET-1 level was positively correlated with CTFC (P<0.05). Multivariate linear regression showed hs-CRP was negatively correlated with the serum level (P<0.05) (r=-0.34). hsCRP and ET-1 levels significantly increased in patients with no-reflow phenomenon.

The automated system for technological process of spacecraft's waveguide paths soldering

NASA Astrophysics Data System (ADS)

Tynchenko, V. S.; Murygin, A. V.; Emilova, O. A.; Bocharov, A. N.; Laptenok, V. D.

2016-11-01

The paper solves the problem of automated process control of space vehicles waveguide paths soldering by means of induction heating. The peculiarities of the induction soldering process are analyzed and necessity of information-control system automation is identified. The developed automated system makes the control of the product heating process, by varying the power supplied to the inductor, on the basis of information about the soldering zone temperature, and stabilizing the temperature in a narrow range above the melting point of the solder but below the melting point of the waveguide. This allows the soldering process automating to improve the quality of the waveguides and eliminate burn-troughs. The article shows a block diagram of a software system consisting of five modules, and describes the main algorithm of its work. Also there is a description of the waveguide paths automated soldering system operation, for explaining the basic functions and limitations of the system. The developed software allows setting of the measurement equipment, setting and changing parameters of the soldering process, as well as view graphs of temperatures recorded by the system. There is shown the results of experimental studies that prove high quality of soldering process control and the system applicability to the tasks of automation.

Laser-based rework in electronics production

NASA Astrophysics Data System (ADS)

Albert, Florian; Mys, Ihor; Schmidt, Michael

2007-02-01

Despite the electronic manufacturing is well-established mass production process for a long time, the problem of reworking, i.a. reject and replace of defect components, still exists. The rework operations (soldering, replacement and desoldering) are performed in most cases manually. However, this practice is characterized by an inconsistent quality of the reworked solder joints and a high degree of physiological stress for the employees. In this paper, we propose a novel full-automated laser based soldering and rework process. Our developed soldering system is a pick-and-place unit with an integrated galvanometer scanner, a fiber coupled diode laser for quasi-simultaneous soldering and a pyrometer-based process control. The developed system provides soldering and reworking processes taking into account a kind of defect, a type of electronic component and quality requirements from the IPC- 610 norm. The paper spends a great deal of efforts to analyze quality of laser reworked solder joints. The quality depends mainly on the type and thickness of intermetallic phases between solder, pads and leads; the wetting angles between pad, solder and lead; and finally, the joint microstructure with its mechanical properties. The influence of the rework soldering on these three factors is discussed and compared to conventional laser soldering results. In order to optimize the quality of reworked joints, the different strategies of energy input are applied.

Processing of NiTi Reinforced Adaptive Solder for Electronic Packaging

DTIC Science & Technology

2004-03-01

NAVAL POSTGRADUATE SCHOOL MONTEREY, CALIFORNIA THESIS PROCESSING OF NITI REINFORCED ADAPTIVE SOLDER FOR ELECTRONIC PACKAGING...March 2004 3. REPORT TYPE AND DATES COVERED Master’s Thesis 4. TITLE AND SUBTITLE: Processing of NiTi Reinforced Adaptive Solder for Electronic...reports in the development a process to fabricate solder joints with a fine distribution of shape memory alloys (SMA) NiTi particulates. The

Diode laser soldering using a lead-free filler material for electronic packaging structures

NASA Astrophysics Data System (ADS)

Chaminade, C.; Fogarassy, E.; Boisselier, D.

2006-04-01

As of today, several lead-free soldering pastes have been qualified for currently used soldering process. Regarding the new potential of laser-assisted soldering processes, the behaviour of the SnAgCu soldering paste requires, however, new investigations. In the first part of this study, the specific temperature profile of a laser soldering process is investigated using a high power diode laser (HPDL). These experimental results are compared to a thermal simulation developed for this specific application. The second part of this work deals with the diffusion of the tin-based filler material through the nickel barrier using the information extracted from the temperature simulations.

A low feed-through 3D vacuum packaging technique with silicon vias for RF MEMS resonators

NASA Astrophysics Data System (ADS)

Zhao, Jicong; Yuan, Quan; Kan, Xiao; Yang, Jinling; Yang, Fuhua

2017-01-01

This paper presents a wafer-level three-dimensional (3D) vacuum packaging technique for radio frequency microelectromechanical systems (RF MEMS) resonators. A Sn-rich Au-Sn solder bonding is employed to provide a vacuum encapsulation as well as electrical conductions. Vertical silicon vias are micro-fabricated by glass reflow process. The optimized grounding, via pitch, and all-round shielding effectively reduce feed-through capacitance. Thus the signal-to-background ratios (SBRs) of the transmission signals increase from 17 dB to 20 dB, and the quality factor (Q) values of the packaged resonators go from around 8000 up to more than 9500. The measured average leak rate and shear strength are (2.55  ±  0.9)  ×  10-8 atm-cc s-1 and 42.53  ±  4.19 MPa, respectively. Furthermore, thermal cycling test between  -40 °C and 100 °C and high temperature storage test at 150 °C show that the resonant-frequency drifts are less than  ±7 ppm. In addition, the SBRs and the Q values have no obvious change after the tests. The experimental results demonstrated that the proposed encapsulation technique is well suited for the applications of RF MEMS devices.

Advanced Flip Chips in Extreme Temperature Environments

NASA Technical Reports Server (NTRS)

Ramesham, Rajeshuni

2010-01-01

The use of underfill materials is necessary with flip-chip interconnect technology to redistribute stresses due to mismatching coefficients of thermal expansion (CTEs) between dissimilar materials in the overall assembly. Underfills are formulated using organic polymers and possibly inorganic filler materials. There are a few ways to apply the underfills with flip-chip technology. Traditional capillary-flow underfill materials now possess high flow speed and reduced time to cure, but they still require additional processing steps beyond the typical surface-mount technology (SMT) assembly process. Studies were conducted using underfills in a temperature range of -190 to 85 C, which resulted in an increase of reliability by one to two orders of magnitude. Thermal shock of the flip-chip test articles was designed to induce failures at the interconnect sites (-40 to 100 C). The study on the reliability of flip chips using underfills in the extreme temperature region is of significant value for space applications. This technology is considered as an enabling technology for future space missions. Flip-chip interconnect technology is an advanced electrical interconnection approach where the silicon die or chip is electrically connected, face down, to the substrate by reflowing solder bumps on area-array metallized terminals on the die to matching footprints of solder-wettable pads on the chosen substrate. This advanced flip-chip interconnect technology will significantly improve the performance of high-speed systems, productivity enhancement over manual wire bonding, self-alignment during die joining, low lead inductances, and reduced need for attachment of precious metals. The use of commercially developed no-flow fluxing underfills provides a means of reducing the processing steps employed in the traditional capillary flow methods to enhance SMT compatibility. Reliability of flip chips may be significantly increased by matching/tailoring the CTEs of the substrate material and the silicon die or chip, and also the underfill materials. Advanced packaging interconnects technology such as flip-chip interconnect test boards have been subjected to various extreme temperature ranges that cover military specifications and extreme Mars and asteroid environments. The eventual goal of each process step and the entire process is to produce components with 100 percent interconnect and satisfy the reliability requirements. Underfill materials, in general, may possibly meet demanding end use requirements such as low warpage, low stress, fine pitch, high reliability, and high adhesion.

A Practical Method for No-Reflow Treatment

PubMed Central

Cetin, Mustafa; Kiziltunc, Emrullah; Güven Cetin, Zehra; Kundi, Harun; Gulkan, Birsen; Cicekcioglu, Hülya

2016-01-01

No-reflow is an undesirable result of percutaneous coronary interventions. Vasoactive drug administration at the distal part of the coronary artery is suggested as a therapeutic option for no-reflow treatment. Here, we represent two cases of successful no-reflow management with previously used monorail balloon at the same procedure as a hand-made distal infusion catheter. PMID:26981291

A Practical Method for No-Reflow Treatment.

PubMed

Cetin, Mustafa; Kiziltunc, Emrullah; Güven Cetin, Zehra; Kundi, Harun; Gulkan, Birsen; Cicekcioglu, Hülya

2016-01-01

No-reflow is an undesirable result of percutaneous coronary interventions. Vasoactive drug administration at the distal part of the coronary artery is suggested as a therapeutic option for no-reflow treatment. Here, we represent two cases of successful no-reflow management with previously used monorail balloon at the same procedure as a hand-made distal infusion catheter.

A family of neuromuscular stimulators with optical transcutaneous control.

PubMed

Jarvis, J C; Salmons, S

1991-01-01

A family of miniature implantable neuromuscular stimulators has been developed using surface-mounted Philips 4000-series integrated circuits. The electronic components are mounted by hand on printed circuits (platinum/gold on alumina) and the electrical connections are made by reflow soldering. The plastic integrated-circuit packages, ceramic resistors and metal interconnections are protected from the body fluids by a coating of biocompatible silicone rubber. This simple technology provides reliable function for at least 4 months under implanted conditions. The circuits have in common a single lithium cell power-supply (3.2 V) and an optical sensor which can be used to detect light flashes through the skin after the device has been implanted. This information channel may be used to switch the output of a device on or off, or to cycle through a series of pre-set programs. The devices are currently finding application in studies which provide an experimental basis for the clinical exploitation of electrically stimulated skeletal muscle in cardiac assistance, sphincter reconstruction or functional electrical stimulation of paralysed limbs.

ECM soldering technologies for small businesses. Final report/project accomplishments summary, project number 93-KCPP-015-E1

DOE Office of Scientific and Technical Information (OSTI.GOV)

Becka, G.A.

1997-03-01

The purpose of this outreach project was to demonstrate, transfer, and educate multiple small and medium-sized US firms in the methodology and technology of environmentally conscious manufacturing soldering techniques. Consultation on replacement solvents for ozone-depleting chemicals, low residue/no clean soldering, and lead-free solder alloys were examples of available FM and T expertise. Depending upon the needs, materials engineering or process engineering help was made available under the program. Requesting businesses could obtain up to 250 hours of assistance from AlliedSignal FM and T on these efforts. The participating companies mainly requested assistance with their immediate needs. Examples of assistance providedmore » included specialized training for their particular product line. FM and T Solder Certification School has an excellent reputation and responded with solder training and help with course outlines for the requesters. One company reported problems soldering certain components. FM and T evaluations determined that the company was received components with solderability levels that did not meet specification rather than experiencing a soldering process problem. Other companies received assistance in incorporating lead-free soldering materials into their production lines and development assistance with fluxless soldering processes. The project was terminated when it was determined that this need could be served by FM and T`s current Technical Assistance Program.« less

[The effect of admission hyperglycemia on coronary reflow in primary percutaneous coronary intervention].

PubMed

Wang, Chang-Hua; Chen, Yun-Dai; Yang, Xin-Chun; Wang, Le-Feng; Wang, Hong-Shi; Sun, Zhi-Jun; Liu, Hong-Bin; Chen, Lian

2011-04-01

To assess the association between admission plasma glucose (APG) and no-reflow during primary percutaneous coronary intervention (PCI) in patients with ST-elevation acute myocardial infarction (STEMI). A total of 1413 patients with STEMI successfully treated with PCI were divided into no-reflow group and normal reflow group. The no-reflow was found in 297 patients (21.0%) of 1413 patients; their APG level was significantly higher than that of the normal reflow group [(13.80 ± 7.47) vs (9.67 ± 5.79) mmol/L, P < 0.0001]. Multivariate logistic regression analysis revealed that current smoking (OR 1.146, 95%CI 1.026 - 1.839, P = 0.031), hyperlipidemia (OR 1.082, 95%CI 1.007 - 1.162, P = 0.032), long reperfusion (> 6 h, OR 1.271, 95%CI 1.158 - 1.403, P = 0.001), admission creatinine clearance (< 90 ml/min, OR 1.046, 95%CI 1.007 - 1.086, P = 0.020), IABP use before PCI (OR 9.346, 95%CI 1.314 - 67.199, P = 0.026), and APG (> 13.0 mmol/L, OR 1.269, 95%CI 1.156 - 1.402, P = 0.027) were the independent no-reflow predictors. The no-reflow incidence was increased as APG increased (14.6% in patients with APG < 7.8 mmol/L and 36.7% in patients with APG > 13.0 mmol/L, P = 0.009). APG > 13.0 mmol/L is an independent no-reflow predictor in patients with STEMI and PPCI.

Multi-objective optimization on laser solder jet bonding process in head gimbal assembly using the response surface methodology

NASA Astrophysics Data System (ADS)

Deeying, J.; Asawarungsaengkul, K.; Chutima, P.

2018-01-01

This paper aims to investigate the effect of laser solder jet bonding parameters to the solder joints in Head Gimbal Assembly. Laser solder jet bonding utilizes the fiber laser to melt solder ball in capillary. The molten solder is transferred to two bonding pads by nitrogen gas. The response surface methodology have been used to investigate the effects of laser energy, wait time, nitrogen gas pressure, and focal position on the shear strength of solder joints and the change of pitch static attitude (PSA). The response surface methodology is employed to establish the reliable mathematical relationships between the laser soldering parameters and desired responses. Then, multi-objective optimization is conducted to determine the optimal process parameters that can enhance the joint shear strength and minimize the change of PSA. The validation test confirms that the predicted value has good agreement with the actual value.

An exploration of the reflow technique for the fabrication of an in vitro microvascular system to study occlusive clots.

PubMed

Li, Yang; Pan, Chuer; Li, Yunfeng; Kumacheva, Eugenia; Ramachandran, Arun

2017-09-08

Embolic ischemia and pulmonary embolism are health emergencies that arise when a particle such as a blood clot occludes a smaller blood vessel in the brain or the lungs, and restricts flow of blood downstream of the vessel. In this work, the reflow technique (Wang et al. Biomed. Microdevices 2007, 9, 657) was adapted to produce a microchannel network that mimics the occlusion process. The technique was first revisited and a simple geometrical model was developed to quantitatively explain the shapes of the resulting microchannels for different reflow parameters. A critical modification was introduced to the reflow protocol to fabricate nearly circular microchannels of different diameters from the same master, which is not possible with the traditional reflow technique. To simulate the phenomenon of occlusion by clots, a microchannel network with three generations of branches with different diameters and branching angles was fabricated, into which fibrin clots were introduced. At low constant pressure drop (ΔP), a clot blocked a branch entrance only partially, while at higher ΔP, the branch was completely blocked. Instances of simultaneous blocking of multiple channels by clots, and the consequent changes in the flow rates in the unblocked branches of the network, were also monitored. This work provides the framework for a systematic study of the distribution of clots in a network, and the rate of dissolution of embolic clots upon the introduction of a thrombolytic drug into the network.

Understanding the Reliability of Solder Joints Used in Advanced Structural and Electronics Applications: Part 2 - Reliability Performance.

DOE PAGES

Vianco, Paul T.

2017-03-01

Whether structural or electronic, all solder joints must provide the necessary level of reliability for the application. The Part 1 report examined the effects of filler metal properties and the soldering process on joint reliability. Filler metal solderability and mechanical properties, as well as the extents of base material dissolution and interface reaction that occur during the soldering process, were shown to affect reliability performance. The continuation of this discussion is presented in this Part 2 report, which highlights those factors that directly affect solder joint reliability. There is the growth of an intermetallic compound (IMC) reaction layer at themore » solder/base material interface by means of solid-state diffusion processes. In terms of mechanical response by the solder joint, fatigue remains as the foremost concern for long-term performance. Thermal mechanical fatigue (TMF), a form of low-cycle fatigue (LCF), occurs when temperature cycling is combined with mismatched values of the coefficient of thermal expansion (CTE) between materials comprising the solder joint “system.” Vibration environments give rise to high-cycle fatigue (HCF) degradation. Although accelerated aging studies provide valuable empirical data, too many variants of filler metals, base materials, joint geometries, and service environments are forcing design engineers to embrace computational modeling to predict the long-term reliability of solder joints.« less

Effect of Elevated Reperfusion Pressure on "No Reflow" Area and Infarct Size in a Porcine Model of Ischemia-Reperfusion.

PubMed

Pantsios, Chris; Kapelios, Chris; Vakrou, Styliani; Diakos, Nikolaos; Pozios, Iraklis; Kontogiannis, Chris; Nanas, John; Malliaras, Konstantinos

2016-07-01

The "no reflow" phenomenon (microvascular obstruction despite restoration of epicardial blood flow) develops postreperfusion in acute myocardial infarction and is associated with poor prognosis. We hypothesized that increased reperfusion pressure may attenuate the no reflow phenomenon, as it could provide adequate flow to overcome the high resistance of the microvasculature within the no reflow zone. Thus, we investigated the effect of modestly elevated blood pressure during reperfusion on the extent of no reflow area and infarct size in a porcine model of ischemia-reperfusion. Eighteen farm pigs underwent acute myocardial infarction by occlusion of the anterior descending coronary artery for 1 hour, followed by 2 hours of reperfusion. Just prior to reperfusion, animals were randomized into 2 groups: in group 1 (control group, n = 9), no intervention was performed. In group 2 (n = 9), aortic pressure was increased by ∼20% (compared to ischemia) by partial clamping of the ascending aorta during reperfusion. Following 2 hours of reperfusion, animals were euthanized to measure area at risk, infarct size, and area of no reflow. Partial clamping of the ascending aorta resulted in modest elevation of blood pressure during reperfusion. The area at risk did not differ between the 2 groups. The no reflow area was significantly increased in group 2 compared to control animals (50% ± 13% vs 37% ± 9% of the area at risk; P = .04). The infarcted area was significantly increased in group 2 compared to control animals (75% ± 17% vs 52% ± 23% of the area at risk; P = .03). Significant positive correlations were observed between systolic aortic pressure and no reflow area, between systolic aortic pressure and infarcted area and between infarcted area and no reflow area during reperfusion. Modestly elevated blood pressure during reperfusion is associated with an increase in no reflow area and in infarct size in a clinically relevant porcine model of ischemia-reperfusion. © The Author(s) 2015.

A wafer-level vacuum package using glass-reflowed silicon through-wafer interconnection for nano/micro devices.

PubMed

Jin, Joo-Young; Yoo, Seung-Hyun; Yoo, Byung-Wook; Kim, Yong-Kweon

2012-07-01

We propose a vacuum wafer-level packaging (WLP) process using glass-reflowed silicon via for nano/micro devices (NMDs). A through-wafer interconnection (TWIn) substrate with silicon vias and reflowed glass is introduced to accomplish a vertical feed-through of device. NMDs are fabricated in the single crystal silicon (SCS) layer which is formed on the TWIn substrate by Au eutectic bonding including Cr adhesion layer. The WLPof the devices is achieved with the capping glass wafer anodically bonded to the SCS layer. In order to demonstrate the successful hermetic packaging, we fabricated the micro-Pirani gauge in the SCS layer, and packaged it in the wafer-level. The vacuum level inside the packaging was measured to be 3.1 Torr with +/- 0.12 Torr uncertainty, and the packaging leakage was not detected during 24 hour after the packaging.

Decapsulation Method for Flip Chips with Ceramics in Microelectronic Packaging

NASA Astrophysics Data System (ADS)

Shih, T. I.; Duh, J. G.

2008-06-01

The decapsulation of flip chips bonded to ceramic substrates is a challenging task in the packaging industry owing to the vulnerability of the chip surface during the process. In conventional methods, such as manual grinding and polishing, the solder bumps are easily damaged during the removal of underfill, and the thin chip may even be crushed due to mechanical stress. An efficient and reliable decapsulation method consisting of thermal and chemical processes was developed in this study. The surface quality of chips after solder removal is satisfactory for the existing solder rework procedure as well as for die-level failure analysis. The innovative processes included heat-sink and ceramic substrate removal, solder bump separation, and solder residue cleaning from the chip surface. In the last stage, particular temperatures were selected for the removal of eutectic Pb-Sn, high-lead, and lead-free solders considering their respective melting points.

Inspection criteria ensure quality control of parallel gap soldering

NASA Technical Reports Server (NTRS)

Burka, J. A.

1968-01-01

Investigation of parallel gap soldering of electrical leads resulted in recommendation on material preparation, equipment, process control, and visual inspection criteria to ensure reliable solder joints. The recommendations will minimize problems in heat-dwell time, amount of solder, bridging conductors, and damage of circuitry.

Influence of solder joint length to the mechanical aspect during the thermal stress analysis

NASA Astrophysics Data System (ADS)

Tan, J. S.; Khor, C. Y.; Rahim, Wan Mohd Faizal Wan Abd; Ishak, Muhammad Ikman; Rosli, M. U.; Jamalludin, Mohd Riduan; Zakaria, M. S.; Nawi, M. A. M.; Aziz, M. S. Abdul; Ani, F. Che

2017-09-01

Solder joint is an important interconnector in surface mount technology (SMT) assembly process. The real time stress, strain and displacement of the solder joint is difficult to observe and assess the experiment. To tackle these problems, simulation analysis was employed to study the von Mises stress, strain and displacement in the thermal stress analysis by using Finite element based software. In this study, a model of leadless electronic package was considered. The thermal stress analysis was performed to investigate the effect of the solder length to those mechanical aspects. The simulation results revealed that solder length gives significant effect to the maximum von Mises stress to the solder joint. Besides, changes in solder length also influence the displacement of the solder joint in the thermal environment. The increment of the solder length significantly reduces the von Mises stress and strain on the solder joint. Thus, the understanding of the physical parameter for solder joint is important for engineer prior to designing the solder joint of the electronic component.

Effect of Embedding Cu-Graphene Hybrid Powder into 2-Phase In-Cu Solders on Its Suitability as Metallic Thermal Interface Material

NASA Astrophysics Data System (ADS)

Sharma, Deepak; Jain, Aman; Somaiah, Nalla; Narayanan, P. Ramesh; Kumar, Praveen

2018-05-01

The effect of embedding Cu-graphene hybrid powder, namely "graphene nano-sheet Cu" (GNS-Cu) powder, into In-40 vol.% Cu solder alloy on the electrical and mechanical properties of In-Cu solder is investigated. GNS-Cu hybrid powders were prepared by mixing reduced graphene oxide powders and CuSO4·5H2O, followed by reduction of the mixture with hydrazine. Subsequently, In-Cu solders with GNS-Cu powders were prepared using a 2-step process, comprising liquid phase sintering (LPS) of In and Cu powders followed by accumulative roll bonding (ARB). During ARB, the GNS-Cu powders were embedded as distinct layers into In-Cu composite solders. Electrical conductivity of the GNS-Cu embedded solders increased by > 20% as compared to pure In-Cu solders processed through the same combination of LPS-ARB steps. The yield strength of In-Cu solder increased by only 10% with the addition of GNS-Cu powders and thus retained the moderate strength often associated with pure In-Cu composite solders. Moreover, the thermal conductivity of GNS-Cu-embedded solders was estimated theoretically to increase by > 60%. These promising findings suggest that GNS-Cu-embedded In-Cu solders can be suitable for next-generation metallic thermal interface material and package-level interconnect applications.

An evaluation of the spring finger solder joints on SA1358-10 and SA2052-4 connector assemblies (MC3617,W87).

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kilgo, Alice C.; Vianco, Paul Thomas; Hlava, Paul Frank

2006-08-01

The SA1358-10 and SA2052-4 circular JT Type plug connectors are used on a number of nuclear weapons and Joint Test Assembly (JTA) systems. Prototype units were evaluated for the following specific defects associated with the 95Sn-5Sb (Sn-Sb, wt.%) solder joint used to attach the beryllium-copper (BeCu) spring fingers to the aluminum (Al) connector shell: (1) extended cracking within the fillet; (2) remelting of the solder joint during the follow-on, soldering step that attached the EMR adapter ring to the connector shell (and/or soldering the EMR shell to the adapter ring) that used the lower melting temperature 63Sn-37Pb (Sn-Pb) alloy; andmore » (3) spalling of the Cd (Cr) layer overplating layer from the fillet surface. Several pedigrees of connectors were evaluated, which represented older fielded units as well as those assemblies that were recently constructed at Kansas City Plant. The solder joints were evaluated that were in place on connectors made with the current soldering process as well as an alternative induction soldering process for attaching the EMR adapter ring to the shell. Very similar observations were made, which crossed the different pedigrees of parts and processes. The extent of cracking in the top side fillets varied between the different connector samples and likely the EMR adapter ring to the shell. Very similar observations were made, which crossed the different pedigrees of parts and processes. The extent of cracking in the top side fillets varied between the different connector samples and likely reflected the different extents to which the connector was mated to its counterpart assembly. In all cases, the spring finger solder joints on the SA1358-10 connectors were remelted as a result of the subsequent EMR adapter ring attachment process. Spalling of the Cd (Cr) overplating layer was also observed for these connectors, which was a consequence of the remelting activity. On the other hand, the SA2052-4 connector did not exhibit evidence of remelting of the spring finger solder joint. The Cd (Cr) layer did not show signs of spalling. These results suggested that, due to the size of the SA1358-10 connector, any of the former or current soldering processes used to attach the EMR adapter ring and/or EMR shell to the connector shell, requires a level of heat energy that will always result in the remelting of the spring finger solder joint attached with either the Sn-Ag or the Sn-Sb alloy. Lastly, it was construed that the induction soldering process, which is used to attach the EMR adapter ring onto the shell, was more likely to have caused the remelting event rather than the more localized heat source of the hand soldering iron used to attach the EMR shell to the adapter ring.« less

Around Marshall

NASA Image and Video Library

1983-08-10

One of the main components of the Hubble Space Telescope (HST) is the Solar Array Drive Electronics (SADE) system. This system interfaces with the Support System Module (SSM) for exchange of operational commands and telemetry data. SADE operates and controls the Solar Array Drive Mechanisms (SADM) for the orientation of the Solar Array Drive (SAD). It also monitors the position of the arrays and the temperature of the SADM. During the first HST servicing mission, the astronauts replaced the SADE component because of some malfunctions. This turned out to be a very challenging extravehicular activity (EVA). Two transistors and two diodes had been thermally stressed with the conformal coating discolored and charred. Soldered cornections became molten and reflowed between the two diodes. The failed transistors gave no indication of defective construction. All repairs were made and the HST was redeposited into orbit. Prior to undertaking this challenging mission, the orbiter's crew trained at Marshall Space Flight Center's (MSFC) Neutral Buoyancy Simulator (NBS) to prepare themselves for working in a low gravity environment. They also practiced replacing HST parts and exercised maneuverability and equipment handling. Pictured are crew members practicing on a space platform.

The Influence of Processing on Strengthening Mechanisms in Pb-Free Solder Joints

NASA Astrophysics Data System (ADS)

Mutuku, Francis; Arfaei, Babak; Cotts, Eric J.

2017-04-01

The number, and the spacing, of Ag3Sn precipitates in Sn-Ag-Cu/Cu solder joints were related to separate processing parameters. The mechanical properties of an individual solder joint were directly related to the resulting distribution of different dispersoids in the joint. As the number of Ag3Sn precipitates increased, so did solder joint strength and shear fatigue lifetime. The room-temperature shear fatigue lifetime was inversely correlated with the separation between Ag3Sn precipitates. Bi and Sb solid solution strengthening was found to result in significantly larger values of shear strength and shear fatigue lifetime for one Pb-free solder. Room-temperature shear fatigue lifetime tests were identified as a relatively straightforward, yet sensitive means to gain insight into the reliability of Sn-Ag-Cu (SAC) solder joints.

Effect of a transient period of ischemia on myocardial cells. II. Fine structure during the first few minutes of reflow.

PubMed

Kloner, R A; Ganote, C E; Whalen, D A; Jennings, R B

1974-03-01

Changes produced in the posterior papillary muscle of the dog following 40 minutes of circumflex artery occlusion and 0 to 20 minutes of blood reflow were studied by electron miroscopy. With no reflow of blood, myocardial cells were modestly swollen, contained amorphous matrix densities in the mitochondria, had aggregation and margination of nuclear chromatin and relaxation of myofibrils. With as little as 2 minutes of blood reflow, cells developed contraction bands and were greatly swollen due to a generalized increase in sarcoplasmic space, formation of vacuoles and swelling of mitochondria. Frequently, cell membranes were lifted away from the myofibers, forming large subsarcolemmal blebs which appeared capable of compressing adjacent capillaries. The extracellular space did not appear to be enlarged, and the marked tissue edema found after reflow was due primarily to accumulation of intracellular fluid. In addition to explosive cell swelling, there was, over the 2- to 20-minute period of reflow, a progressive increase in size and number of granular mitochondrial dense bodies of the calcium accumulation type. No significant changes in lysosomes were observed. The speed with which the morphologic changes developed during very early reflow periods suggests that irreversible ischemic injury produces a defect in cell volume regulation during the phase of ischemia and that this defect becomes manifest if arterial flow is restored to the affected cells.

Phase diagrams for lead-free solder alloys

NASA Astrophysics Data System (ADS)

Kattner, Ursula R.

2002-12-01

The need for new, improved solder alloys and a better understanding of reactions during the soldering process grows steadily as the need for smaller and more reliable electronic products increases. Information obtained from phase equilibria data and thermodynamic calculations has proven to be an important tool in the design and understanding of new lead-free solder alloys. A wide range of candidate alloys can be rapidly evaluated for proper freezing ranges, susceptibility to contamination effects, and reactions with substrate materials before the expensive process of preparing and testing candidate alloys is initiated.

Coronary artery ectasia, an independent predictor of no-reflow after primary PCI for ST-elevation myocardial infarction.

PubMed

Schram, H C F; Hemradj, V V; Hermanides, R S; Kedhi, E; Ottervanger, J P

2018-04-25

The no-reflow phenomenon is a serious complication after primary percutaneous coronary intervention (PCI) for ST-elevation Myocardial Infarction (STEMI). Coronary artery ectasia (CAE) may increase the risk of no-reflow, however, only limited data is available on the potential impact of CAE. The aim of this study was to determine the potential association between CAE and no-reflow after primary PCI. A case control study was performed based on a prospective cohort of STEMI patients from January 2000 to December 2011. All patients with TIMI 0-1 flow post primary PCI, in the absence of dissection, thrombus, spasm or high-grade residual stenosis, were considered as no-reflow case. Control subjects were two consecutive STEMI patients after each case, with TIMI flow ≥2 after primary PCI. CAE was defined as dilatation of an arterial segment to a diameter at least 1.5 times that of the adjacent normal coronary artery. In the no-reflow group, frequency of CAE was significantly higher (33.8% vs 3.9%, p < 0.001) compared to the control group. Baseline variables were comparable between patients with and without CAE. Patients with CAE had more often TIMI 0-1 flow pre-PCI (91% vs 71% p = 0.03), less often anterior STEMI (3% vs 37%, p < 0.001) and underwent significantly less often a PCI with stenting (47% vs 74%, p = 0.003). After multivariate analysis, CAE remained a strong and independent predictor of no-reflow (OR 13.9, CI 4.7-41.2, p < 0.001). CAE is a strong and independent predictor of no-reflow after primary PCI for STEMI. Future studies should assess optimal treatment. Copyright © 2017 Elsevier B.V. All rights reserved.

Automation of experimental research of waveguide paths induction soldering

NASA Astrophysics Data System (ADS)

Tynchenko, V. S.; Petrenko, V. E.; Kukartsev, V. V.; Tynchenko, V. V.; Antamoshkin, O. A.

2018-05-01

The article presents an automated system of experimental studies of the waveguide paths induction soldering process. The system is a part of additional software for a complex of automated control of the technological process of induction soldering of thin-walled waveguide paths from aluminum alloys, expanding its capabilities. The structure of the software product, the general appearance of the controls and the potential application possibilities are presented. The utility of the developed application by approbation in a series of field experiments was considered and justified. The application of the experimental research system makes it possible to improve the process under consideration, providing the possibility of fine-tuning the control regulators, as well as keeping the statistics of the soldering process in a convenient form for analysis.

Reliability analysis of different structure parameters of PCBA under drop impact

NASA Astrophysics Data System (ADS)

Liu, P. S.; Fan, G. M.; Liu, Y. H.

2018-03-01

The establishing process of PCBA is modelled by finite element analysis software ABAQUS. Firstly, introduce the Input-G method and the fatigue life under drop impact are introduced and the mechanism of the solder joint failure in the process of drop is analysed. The main reason of solder joint failure is that the PCB component is suffering repeated tension and compression stress during the drop impact. Finally, the equivalent stress and peel stress of different solder joint and plate-level components under different impact acceleration are also analysed. The results show that the reliability of tin-silver copper joint is better than that of tin- lead solder joint, and the fatigue life of solder joint expectancy decrease as the impact pulse amplitude increases.

The Effect of Copper Addition on the Properties of Sn-0.7Cu Solder Paste

NASA Astrophysics Data System (ADS)

Said, R. M.; Mohamad Johari, F. H.; Salleh, M. A. A. Mohd; Sandu, A. V.

2018-03-01

The effect of copper addition on the properties of Sn-Cu based solder paste were investigate through this study. The Sn-0.7Cu solder paste doped with different concentration of Cu were prepared using solder paste mixture. The bulk solder microstructure of assolidified solder paste was studied. Besides that, intermetallic compound (IMC) formation on Cu substrate and hardness of all solder paste also being investigated. Results shows that increasing Cu concentration cause formation of large Cu6Sn5 IMC at bulk solder and the size of the IMC grew larger at high temperature. In addition, β-Sn area reduce when Cu concentration was high. The IMC morphology for all solder paste almost remain unchanged. However, there are large Cu6Sn5 IMC form near the interfacial IMC in Sn-Cu solder paste with high amount of Cu (Sn-10Cu). The hardness value was decrease when processing temperature at 250 °C due to present of small void in the microstructure while hardness of solder material increased at high temperature.

Evaluation of low-residue soldering for military and commercial applications: A report from the Low-Residue Soldering Task Force

DOE Office of Scientific and Technical Information (OSTI.GOV)

Iman, R.L.; Anderson, D.J.; Burress, R.V.

1995-06-01

The LRSTF combined the efforts of industry, military, and government to evaluate low-residue soldering processes for military and commercial applications. These processes were selected for evaluation because they provide a means for the military to support the presidential mandate while producing reliable hardware at a lower cost. This report presents the complete details and results of a testing program conducted by the LRSTF to evaluate low-residue soldering for printed wiring assemblies. A previous informal document provided details of the test plan used in this evaluation. Many of the details of that test plan are contained in this report. The testmore » data are too massive to include in this report, however, these data are available on disk as Excel spreadsheets upon request. The main purpose of low-residue soldering is to eliminate waste streams during the manufacturing process.« less

Solderability study of RABiTS-based YBCO coated conductors

NASA Astrophysics Data System (ADS)

Zhang, Yifei; Duckworth, Robert C.; Ha, Tam T.; Gouge, Michael J.

2011-08-01

The solderability of commercially available YBa2Cu3O7-x (YBCO) coated conductors that were made from Rolling Assisted Biaxially Textured Substrates (RABiTS)-based templates was studied. The coated conductors, also known as second-generation (2G) high temperature superconductor (HTS) wires (in the geometry of flat tapes about 4 mm wide), were laminated with copper, brass, or stainless steel strips as stabilizers. To understand the factors that influence their solderability, surface profilometry and scanning electron microscopy were used to characterize the wire surfaces. The solderability of three solders, 52In48Sn, 67Bi33In, and 100In (wt.%), was evaluated using a standard test (IPC/ECA J-STD-002) and with two different commercial fluxes. It was found that the solderability varied with the solder and flux but the three different wires showed similar solderability for a fixed combination of solder and flux. Solder joints of the 2G wires were fabricated using the tools and the procedures recommended by the HTS wire manufacturer. The solder joints were made in a lap-joint geometry and with the superconducting sides of the two wires face-to-face. The electrical resistances of the solder joints were measured at 77 K, and the results were analyzed to qualify the soldering materials and evaluate the soldering process. It was concluded that although the selection of soldering materials affected the resistance of a solder joint, the resistivity of the stabilizer was the dominant factor.

Solderability Study of RABiTS-Based YBCO Coated Conductors

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhang, Yifei; Duckworth, Robert C; Ha, Tam T

2011-01-01

The solderability of commercially available YBa{sub 2}Cu{sub 3}O{sub 7-x} (YBCO) coated conductors that were made from Rolling Assisted Biaxially Textured Substrates (RABiTS)-based templates was studied. The coated conductors, also known as second-generation (2G) high temperature superconductor (HTS) wires (in the geometry of flat tapes about 4 mm wide), were laminated with copper, brass, or stainless steel strips as stabilizers. To understand the factors that influence their solderability, surface profilometry and scanning electron microscopy were used to characterize the wire surfaces. The solderability of three solders, 52In48Sn, 67Bi33In, and 100In (wt.%), was evaluated using a standard test (IPC/ECA J-STD-002) and withmore » two different commercial fluxes. It was found that the solderability varied with the solder and flux but the three different wires showed similar solderability for a fixed combination of solder and flux. Solder joints of the 2G wires were fabricated using the tools and the procedures recommended by the HTS wire manufacturer. The solder joints were made in a lap-joint geometry and with the superconducting sides of the two wires face-to-face. The electrical resistances of the solder joints were measured at 77 K, and the results were analyzed to qualify the soldering materials and evaluate the soldering process. It was concluded that although the selection of soldering materials affected the resistance of a solder joint, the resistivity of the stabilizer was the dominant factor.« less

A comparison of two soldering techniques on the misfit of bar-retained implant-supported overdentures.

PubMed

Alvarez, Angel; Lafita, Pedro; de Llanos, Hector; Gago, Angel; Brizuela, Aritza; Ellacuria, Joseba J

2014-02-01

This study was conducted to measure and compare the effect of the soldering method (torch soldering or ceramic furnace soldering) used for soldering bars to bar-retained, implant-supported overdentures on the fit between the bar gold cylinder and implant transgingival abutment. Thirty-two overdenture implant bars were manufactured and screw retained into two Bränemark implants, which were attached to a cow rib. The bars were randomly distributed in two groups: a torch-soldering group and a porcelain-furnace soldering group. Then all bars were cut and soldered using a torch and a ceramic furnace. The fit between the bar gold cylinders and implant transgingival abutments was measured with a light microscope on the opposite side to the screw tightening side before and after the bar soldering procedure. The data obtained were statistically processed for paired and independent data. The average misfit for all bars before soldering was 33.83 to 54.04 μm. After cutting and soldering the bars, the misfit increased up to a range of 71.74 to 78.79 μm. Both before and after the soldering procedure, the bars soldered using a torch showed a higher misfit when compared to the bars soldered using a porcelain furnace. After the soldering procedure, the misfit was slightly lower on the left side of the bars, which had been soldered using a ceramic furnace. According to our data, the soldering of bars using the torch or furnace oven soldering techniques does not improve the misfit of one-piece cast bars on two implants. The lower misfit was obtained using the porcelain furnace soldering technique. © 2013 by the American College of Prosthodontists.

Solder extrusion pressure bonding process and bonded products produced thereby

DOEpatents

Beavis, L.C.; Karnowsky, M.M.; Yost, F.G.

1992-06-16

Disclosed is a process for production of soldered joints which are highly reliable and capable of surviving 10,000 thermal cycles between about [minus]40 C and 110 C. Process involves interposing a thin layer of a metal solder composition between the metal surfaces of members to be bonded and applying heat and up to about 1000 psi compression pressure to the superposed members, in the presence of a reducing atmosphere, to extrude the major amount of the solder composition, contaminants including fluxing gases and air, from between the members being bonded, to form a very thin, strong intermetallic bonding layer having a thermal expansion tolerant with that of the bonded members.

Study on Joint Interface and Mechanical Properties of Cu/Pb-Sn/Cu Lap Joint Produced by Friction Stir Soldering Process

NASA Astrophysics Data System (ADS)

Sarkari Khorrami, Mahmoud; Kokabi, Amir Hossein; Movahedi, Mojtaba

2015-05-01

In this work, friction stir soldering (FSS) as a new approach for fabrication of copper/copper lap joints was introduced. This process is principally based on the friction stir processing (FSP) that can be performed using FSP tools with and without pin on the top sheet. In the present study, Pb-Sn foil was used as a solder which would be melted and then extruded in the area between the copper sheets during FSS process. This process was carried out using tools with and without pin at various rotation speeds of 1200, 1400, and 1600 rpm and traverse speed of 32 mm/min. Also, the same joint was fabricated using furnace soldering to compare the mechanical properties obtained with FSS and furnace soldering processes. It was observed that FSS possesses some advantages over the conventional furnace soldering process including the formation of more bond area at the interface corresponding to the higher fracture load of FSS joints compared with furnace soldering one. Moreover, it was concluded that the thickness of intermetallic compounds (IMCs) and the formation of voids at the joint interface were the predominant factor determining the mechanical properties of the FSS joints produced by FSS tool with and without pin, respectively. The microstructural examinations revealed that Cu-Sn IMCs of Cu3Sn and Cu6Sn5 were formed at the joint interface. It was observed that the FSS joint produced by tool with pin experienced the more peak temperature in comparison with that produced by pin-free tool. This may lead to the formation of thicker IMCs at the interface. Of course, the thickness of IMCs can be controlled by choosing proper FSS parameters, especially the rotation speed of the tool.

High-performance 193-nm photoresist materials based on ROMA polymers: sub-90-nm contact hole application with resist reflow

NASA Astrophysics Data System (ADS)

Joo, Hyun S.; Seo, Dong C.; Kim, Chang M.; Lim, Young T.; Cho, Seong D.; Lee, Jong B.; Song, Ji Y.; Kim, Kyoung M.; Park, Joo H.; Jung, Jae Chang; Shin, Ki S.; Bok, Cheol Kyu; Moon, Seung C.

2004-05-01

There are numerous methods being explored by lithographers to achieve the patterning of sub-90nm contact hole features. Regarding optical impact on contact imaging, various optical extension techniques such as assist features, focus drilling, phase shift masks, and off-axis illumination are being employed to improve the aerial image. One possible option for improving of the process window in contact hole patterning is resist reflow. We have already reported the resist using a ring opened polymer of maleic anhydride unit(ROMA) during the past two years in this conference. It has several good properties such as UV transmittance, PED stability, solubility and storage stability. The resist using ROMA polymer as a matrix resin showed a good lithographic performance at C/H pattern and one of the best characteristics in a ROMA polymer is the property of thermal shrinkage. It has a specific glass transition temperature(Tg) each polymers, so they made a applying of resist reflow technique to print sub-90nm C/H possible. Recently, we have researched about advanced ROMA polymer(ROMA II), which is composed of cycloolefine derivatives with existing ROMA type polymer(ROMA I), for dry etch resistance increasing, high resolution, and good thermal shrinkage property. In this paper, we will present the structure, thermal shrinkage properties, Tg control, material properties for ROMA II polymer and will show characteristics, the lithographic performance for iso and dense C/H applications of the resist using ROMA II polymer. In addition, we will discuss resist reflow data gained at C/H profile of sub-90nm sizes, which has good process window.

Intracoronary bivalirudin for no reflow reversal: a second chance to treat this disorder?

PubMed

Cortese, Bernardo; Picchi, Andrea; Micheli, Andrea; Limbruno, Ugo

2009-07-01

No reflow, defined as failure to restore normal myocardial blood flow despite removal of coronary obstruction, is a not rare complication of ST-elevation acute myocardial infarction. We here describe the case of an old patient experiencing inferior and right ventricle myocardial infarction complicated by cardiogenic shock, anaemia and thrombocytopenia. We managed it with urgent PCI using thrombus aspirator, that determined onset of no reflow, that we successfully managed with intracoronary bivalirudin. We showed how bivalirudin, a drug whose use is increasing in the catheterization laboratories, could be safely used via the intracoronary route to treat no reflow phenomenon due to distal microembolization in a complex patient.

Welding, brazing, and soldering handbook

NASA Technical Reports Server (NTRS)

Kilgore, A. B.; Koehler, M. L.; Metzler, J. W.; Sturges, S. R.

1969-01-01

Handbook gives information on the selection and application of welding, brazing, and soldering techniques for joining various metals. Summary descriptions of processes, criteria for process selection, and advantages of different methods are given.

Ab initio-aided CALPHAD thermodynamic modeling of the Sn-Pb binary system under current stressing

PubMed Central

Lin, Shih-kang; Yeh, Chao-kuei; Xie, Wei; Liu, Yu-chen; Yoshimura, Masahiro

2013-01-01

Soldering is an ancient process, having been developed 5000 years ago. It remains a crucial process with many modern applications. In electronic devices, electric currents pass through solder joints. A new physical phenomenon – the supersaturation of solders under high electric currents – has recently been observed. It involves (1) un-expected supersaturation of the solder matrix phase, and (2) the formation of unusual “ring-shaped” grains. However, the origin of these phenomena is not yet understood. Here we provide a plausible explanation of these phenomena based on the changes in the phase stability of Pb-Sn solders. Ab initio-aided CALPHAD modeling is utilized to translate the electric current-induced effect into the excess Gibbs free energies of the phases. Hence, the phase equilibrium can be shifted by current stressing. The Pb-Sn phase diagrams with and without current stressing clearly demonstrate the change in the phase stabilities of Pb-Sn solders under current stressing. PMID:24060995

Independent no-reflow predictors in female patients with ST-elevation acute myocardial infarction treated with primary percutaneous coronary intervention.

PubMed

Chen, Yundai; Wang, Changhua; Yang, Xinchun; Wang, Lefeng; Sun, Zhijun; Liu, Hongbin; Chen, Lian

2012-05-01

Independent no-reflow predictors should be evaluated in female patients with ST-segment elevation acute myocardial infarction (STEMI) and successfully treated with primary percutaneous coronary intervention (PPCI) in the current interventional equipment and techniques, thus to be constructed a no-reflow predicting model. In this study, 320 female patients with STEMI were successfully treated with PPCI within 12 h after the onset of AMI from 2007 to 2010. All clinical, angiographic, and procedural data were collected. Multiple logistic regression analysis was used to identify independent no-reflow predictors. The no-reflow was found in 81 (25.3%) of 320 female patients. Univariate and multivariate stepwise logistic regression analysis identified that low SBP on admission <100 mmHg (OR 1.991, 95% CI 1.018-3.896; p = 0.004), target lesion length >20 mm (OR 1.948, 95% CI 1.908-1.990; p = 0.016), collateral circulation 0-1 (OR 1.952, 95% CI 1.914-1.992; p = 0.019), pre-PCI thrombus score ≥ 4 (OR 4.184, 95% CI 1.482-11.813; p = 0.007), and IABP use before PCI (OR 1.949, 95% CI 1.168-3.253; p = 0.011) were independent no-reflow predictors. The no-reflow incidence significantly increased as the numbers of independent predictors increased [0% (0/2), 10.8% (9/84), 14.5% (17/117), 37.7% (29/77), 56.7% (17/30), and 81.8% (9/11) in female patients with 0, 1, 2, 3, 4, and 5 independent predictors, respectively; p < 0.0001]. The five no-reflow predicting variables were admission SBP <100 mmHg, target lesion length >20 mm, collateral circulation 0-1, pre-PCI thrombus score ≥ 4, and IABP use before PCI in female patients with STEMI treated with PPCI.

Solder extrusion pressure bonding process and bonded products produced thereby

DOEpatents

Beavis, Leonard C.; Karnowsky, Maurice M.; Yost, Frederick G.

1992-01-01

Production of soldered joints which are highly reliable and capable of surviving 10,000 thermal cycles between about -40.degree. C. and 110.degree. C. Process involves interposing a thin layer of a metal solder composition between the metal surfaces of members to be bonded and applying heat and up to about 1000 psi compression pressure to the superposed members, in the presence of a reducing atmosphere, to extrude the major amount of the solder composition, contaminants including fluxing gases and air, from between the members being bonded, to form a very thin, strong intermetallic bonding layer having a thermal expansion tolerant with that of the bonded members.

Solder extrusion pressure bonding process and bonded products produced thereby

NASA Astrophysics Data System (ADS)

Beavis, L. C.; Karnowsky, M. M.; Yost, F. G.

1990-04-01

The production of soldered joints are highly reliable and capable of surviving 10,000 thermal cycles between about -40 and 110 C. The process involves interposing a thin layer of a metal solder composition between the metal surfaces of members to be bonded and applying heat up to about 1000 psi compression pressure to the superposed members, in the presence of a reducing atmosphere, to extrude the major amount of the solder composition, contaminants including fluxing gases and air, from between the members being bonded, to form a very thin, strong intermetallic bonding layer having a thermal expansion tolerant with that of the bonded members.

Comparative shear tests of some low temperature lead-free solder pastes

NASA Astrophysics Data System (ADS)

Branzei, Mihai; Plotog, Ioan; Varzaru, Gaudentiu; Cucu, Traian C.

2016-12-01

The range of electronic components and as a consequence, all parts of automotive electronic equipment operating temperatures in a vehicle is given by the location of that equipment, so the maximum temperature can vary between 358K and 478K1. The solder joints could be defined as passive parts of the interconnection structure of automotive electronic equipment, at a different level, from boards of electronic modules to systems. The manufacturing costs reduction necessity and the RoHS EU Directive3, 7 consequences generate the trend to create new Low-Temperature Lead-Free (LTLF) solder pastes family9. In the paper, the mechanical strength of solder joints and samples having the same transversal section as resistor 1206 case type made using the same LTLF alloys into Vapour Phase Soldering (VPS) process characterized by different cooling rates (slow and rapid) and two types of test PCBs pads finish, were benchmarked at room temperature. The presented work extends the theoretical studies and experiments upon heat transfer in VPSP in order to optimize the technology for soldering process (SP) of automotive electronic modules and could be extended for home and modern agriculture appliances industry. The shear forces (SF) values of the LTLF alloy samples having the same transversal section as resistor 1206 case type will be considered as references values of a database useful in the new solder alloy creation processes and their qualification for automotive electronics domain.

Safer Soldering Guidelines and Instructional Resources

ERIC Educational Resources Information Center

Love, Tyler S.; Tomlinson, Joel

2018-01-01

Soldering is a useful and necessary process for many classroom, makerspace, Fab Lab, technology and engineering lab, and science lab activities. As described in this article, soldering can pose many safety risks without proper engineering controls, standard operating procedures, and direct instructor supervision. There are many safety hazards…

Interfacial Reaction and Mechanical Properties of Sn-Bi Solder joints

PubMed Central

Huang, Ying; Zhang, Zhijie

2017-01-01

Sn-Bi solder with different Bi content can realize a low-to-medium-to-high soldering process. To obtain the effect of Bi content in Sn-Bi solder on the microstructure of solder, interfacial behaviors in solder joints with Cu and the joints strength, five Sn-Bi solders including Sn-5Bi and Sn-15Bi solid solution, Sn-30Bi and Sn-45Bi hypoeutectic and Sn-58Bi eutectic were selected in this work. The microstructure, interfacial reaction under soldering and subsequent aging and the shear properties of Sn-Bi solder joints were studied. Bi content in Sn-Bi solder had an obvious effect on the microstructure and the distribution of Bi phases. Solid solution Sn-Bi solder was composed of the β-Sn phases embedded with fine Bi particles, while hypoeutectic Sn-Bi solder was composed of the primary β-Sn phases and Sn-Bi eutectic structure from networked Sn and Bi phases, and eutectic Sn-Bi solder was mainly composed of a eutectic structure from short striped Sn and Bi phases. During soldering with Cu, the increase on Bi content in Sn-Bi solder slightly increased the interfacial Cu6Sn5 intermetallic compound (IMC)thickness, gradually flattened the IMC morphology, and promoted the accumulation of more Bi atoms to interfacial Cu6Sn5 IMC. During the subsequent aging, the growth rate of the IMC layer at the interface of Sn-Bi solder/Cu rapidly increased from solid solution Sn-Bi solder to hypoeutectic Sn-Bi solder, and then slightly decreased for Sn-58Bi solder joints. The accumulation of Bi atoms at the interface promoted the rapid growth of interfacial Cu6Sn5 IMC layer in hypoeutectic or eutectic Sn-Bi solder through blocking the formation of Cu6Sn5 in solder matrix and the transition from Cu6Sn5 to Cu3Sn. Ball shear tests on Sn-Bi as-soldered joints showed that the increase of Bi content in Sn-Bi deteriorated the shear strength of solder joints. The addition of Bi into Sn solder was also inclined to produce brittle morphology with interfacial fracture, which suggests that the addition of Bi increased the shear resistance strength of Sn-Bi solder. PMID:28792440

Controlling intermetallic compound growth in SnAgCu/Ni-P solder joints by nanosized Cu6Sn5 addition

NASA Astrophysics Data System (ADS)

Kao, Szu-Tsung; Lin, Yung-Chi; Duh, Jenq-Gong

2006-03-01

Nanosized Cu6Sn5 dispersoids were incorporated into Sn and Ag powders and milled together to form Sn-3Ag-0.5Cu composite solders by a mechanical alloying process. The aim of this study was to investigate the interfacial reaction between SnAgCu composite solder and electroless Ni-P/Cu UBM after heating for 15 min. at 240°C. The growth of the IMCs formed at the composite solder/EN interface was retarded as compared to the commercial Sn3Ag0.5Cu solder joints. With the aid of the elemental distribution by x-ray color mapping in electron probe microanalysis (EPMA), it was revealed that the SnAgCu composite solder exhibited a refined structure. It is proposed that the Cu6Sn5 additives were pinned on the grain boundary of Sn after heat treatment, which thus retarded the movement of Cu toward the solder/EN interface to form interfacial compounds. In addition, wetting is an essential prerequisite for soldering to ensure good bonding between solder and substrate. It was demonstrated that the contact angles of composite solder paste was <25°, and good wettability was thus assured.

Reliability Study of Solder Paste Alloy for the Improvement of Solder Joint at Surface Mount Fine-Pitch Components.

PubMed

Rahman, Mohd Nizam Ab; Zubir, Noor Suhana Mohd; Leuveano, Raden Achmad Chairdino; Ghani, Jaharah A; Mahmood, Wan Mohd Faizal Wan

2014-12-02

The significant increase in metal costs has forced the electronics industry to provide new materials and methods to reduce costs, while maintaining customers' high-quality expectations. This paper considers the problem of most electronic industries in reducing costly materials, by introducing a solder paste with alloy composition tin 98.3%, silver 0.3%, and copper 0.7%, used for the construction of the surface mount fine-pitch component on a Printing Wiring Board (PWB). The reliability of the solder joint between electronic components and PWB is evaluated through the dynamic characteristic test, thermal shock test, and Taguchi method after the printing process. After experimenting with the dynamic characteristic test and thermal shock test with 20 boards, the solder paste was still able to provide a high-quality solder joint. In particular, the Taguchi method is used to determine the optimal control parameters and noise factors of the Solder Printer (SP) machine, that affects solder volume and solder height. The control parameters include table separation distance, squeegee speed, squeegee pressure, and table speed of the SP machine. The result shows that the most significant parameter for the solder volume is squeegee pressure (2.0 mm), and the solder height is the table speed of the SP machine (2.5 mm/s).

Reliability Study of Solder Paste Alloy for the Improvement of Solder Joint at Surface Mount Fine-Pitch Components

PubMed Central

Rahman, Mohd Nizam Ab.; Zubir, Noor Suhana Mohd; Leuveano, Raden Achmad Chairdino; Ghani, Jaharah A.; Mahmood, Wan Mohd Faizal Wan

2014-01-01

The significant increase in metal costs has forced the electronics industry to provide new materials and methods to reduce costs, while maintaining customers’ high-quality expectations. This paper considers the problem of most electronic industries in reducing costly materials, by introducing a solder paste with alloy composition tin 98.3%, silver 0.3%, and copper 0.7%, used for the construction of the surface mount fine-pitch component on a Printing Wiring Board (PWB). The reliability of the solder joint between electronic components and PWB is evaluated through the dynamic characteristic test, thermal shock test, and Taguchi method after the printing process. After experimenting with the dynamic characteristic test and thermal shock test with 20 boards, the solder paste was still able to provide a high-quality solder joint. In particular, the Taguchi method is used to determine the optimal control parameters and noise factors of the Solder Printer (SP) machine, that affects solder volume and solder height. The control parameters include table separation distance, squeegee speed, squeegee pressure, and table speed of the SP machine. The result shows that the most significant parameter for the solder volume is squeegee pressure (2.0 mm), and the solder height is the table speed of the SP machine (2.5 mm/s). PMID:28788270

Growth differentiation factor 15 may protect the myocardium from no-reflow by inhibiting the inflammatory-like response that predominantly involves neutrophil infiltration

PubMed Central

ZHANG, MEI; PAN, KUNYING; LIU, QIANPING; ZHOU, XIN; JIANG, TIEMIN; LI, YUMING

2016-01-01

The aim of the current study was to investigate the time course of the expression of growth differentiation factor-15 (GDF-15) in rat ischemic myocardium with increasing durations of reperfusion, and to elucidate its physiopathological role in the no-reflow phenomenon. Wistar rats were randomly divided into ischemia reperfusion (I/R) and sham groups, and myocardial I/R was established by ligation of the left anterior descending coronary artery for 1 h followed by reperfusion for 2, 4, 6, 12, 24 h and 7 days whilst rats in the sham group were subjected to a sham operation. The expression levels of GDF-15 and ICAM-1 were measured, in addition to myeloperoxidase (MPO) activity. The myocardial anatomical no-reflow and infarction areas were assessed. The area at risk was not significantly different following various periods of reperfusion, while the infarct area and no-reflow area were significantly greater following 6 h of reperfusion (P<0.05). The mRNA and protein expression levels of GDF-15 were increased during the onset and development of no-reflow, and peaked following 24 h of reperfusion. MPO activity was reduced with increasing reperfusion duration, while ICAM-1 levels were increased. Hematoxylin and eosin staining demonstrated that myocardial neutrophil infiltration was significantly increased by I/R injury, in particular following 2, 4 and 6 h of reperfusion. GDF-15 expression levels were negatively correlated with MPO activity (r=−0.55, P<0.001), and the MPO activity was negatively correlated with the area of no-reflow (r=−0.46, P<0.01). By contrast, GDF-15 was significantly positively correlated with ICAM-1 levels (r=0.52, P<0.01), which additionally were demonstrated to be significantly positively associated with the size of the no-reflow area (r= 0.39, P<0.05). The current study demonstrated the time course effect of reperfusion on the expression of GDF-15 in the myocardial I/R rat model, with the shorter reperfusion times (6 h) resulting in significant no-reflow in ischemic myocardium. GDF-15 may protect the I/R myocardium from no-reflow by inhibiting the inflammatory-like response, which involves neutrophil infiltration and transendothelial migration. PMID:26647773

A no-reflow prediction model in patients with ST-elevation acute myocardial infarction and primary drug-eluting stenting.

PubMed

Wang, Chang-Hua; Chen, Yun-Dai; Yang, Xin-Chun; Wang, Le-Feng; Wang, Hong-Shi; Sun, Zhi-Jun; Liu, Hong-Bin

2011-04-01

This study was undertaken to assess independent no-reflow predictors in patients with ST-elevation acute myocardial infarction (STEMI) and primary drug-eluting stenting in the current interventional strategies. One thousand four hundred and thirteen patients with STEMI were successfully treated with primary drug-eluting stenting within 12 h after AMI. All clinical, angiographic and procedural data were collected. Univariate and multivariate logistic regression was used to identify independent no-reflow predictors. The no-reflow was found in 297 (21%) of 1413 patients. Univariate and multivariate logistic regression identified that age (>65 years, OR 1.47, 95% CI 1.46-1.49; p = 0.007), long time-to-reperfusion (>6 h, OR 1.27, 95% CI 1.16-1.40; p = 0.001), admission plasma glucose (>13.0 mmol/L, OR 1.27, 95% CI 1.16-1.40; p = 0.027), collateral circulation (0-1, OR 1.69, 95% CI 1.25-2.29; p = 0.001), pre-PCI thrombus score (≥4, OR 1.36, 95% CI 1.16-1.79; p = 0.011), and IABP use before PCI (OR 2.89, 95% CI 1.65-5.05; p < 0.0001) were independent no-reflow predictors. The no-reflow rate significantly increased as the number of independent predictors increased (0%, 6%, 15%, 25%, 40%, 50% and 100% in patients with 0, 1, 2, 3, 4, 5, and 6 independent predictors, respectively; p < 0.0001). The prediction model consisted of six no-reflow predictors in patients with STEMI and primary drug-eluting stenting and should be confirmed in large-scale prospective studies.

Comparison of no-reflow phenomenon after percutaneous coronary intervention for acute myocardial infarction between smokers and nonsmokers.

PubMed

Shemirani, Hassan; Tafti, Faezeh Dehghani; Amirpour, Afshin

2014-11-01

No-reflow phenomenon after percutaneous coronary intervention (PCI) in patients with acute ST-segment-elevation myocardial infarction (STEMI) is relatively common and has therapeutic and prognostic implications. Cigarette smoking is known as deleterious in patients with coronary artery disease (CAD), but the effect of smoking on no-reflow phenomenon is less investigated. The aim of this study was to compare no-reflow phenomenon after percutneous coronary intervention for acute myocardial infarction, between smokers and non smokers. A total of 141 patients who were admitted to Chamran Hospital (Isfahan, Iran) between March and September, 2012 with a diagnosis of STEMI, enrolled into our Cohort study. Patients were divided into current smoker and nonsmoker groups (based on patient's information). All patients underwent primary PCI or rescue PCI within the first 12-h of chest pain. No-reflow phenomenon, thrombolysis in myocardial infarction (MI) flow, and 24-h complications were assessed in both groups. A total of 47 current smoker cases (32.9%) and 94 (65.7%) nonsmoker cases were evaluated. Smokers in comparison to nonsmokers were younger (53.47 ± 10.59 vs. 61.46 ± 10.55, P < 0.001) and they were less likely to be hypertensive (15.2% vs. 44.7%, P < 0.001), diabetic (17% vs. 36.2%, P < 0.05), and female gender (4.3% vs. 25.5%, P < 0.01). Angiographic and procedural characteristics of both groups were similar. 9 patients died during the first 24-h after PCI (4.3% of smokers and 6.4% of nonsmokers, P: 0.72). No-reflow phenomenon was observed in 29.8% of current smokers and 31.5% of nonsmokers (P = 0.77). No-reflow phenomenon or short-term complications were not significantly different between current smokers and non smokers.

Solution-Processed Transistors Using Colloidal Nanocrystals with Composition-Matched Molecular "Solders": Approaching Single Crystal Mobility.

PubMed

Jang, Jaeyoung; Dolzhnikov, Dmitriy S; Liu, Wenyong; Nam, Sooji; Shim, Moonsub; Talapin, Dmitri V

2015-10-14

Crystalline silicon-based complementary metal-oxide-semiconductor transistors have become a dominant platform for today's electronics. For such devices, expensive and complicated vacuum processes are used in the preparation of active layers. This increases cost and restricts the scope of applications. Here, we demonstrate high-performance solution-processed CdSe nanocrystal (NC) field-effect transistors (FETs) that exhibit very high carrier mobilities (over 400 cm(2)/(V s)). This is comparable to the carrier mobilities of crystalline silicon-based transistors. Furthermore, our NC FETs exhibit high operational stability and MHz switching speeds. These NC FETs are prepared by spin coating colloidal solutions of CdSe NCs capped with molecular solders [Cd2Se3](2-) onto various oxide gate dielectrics followed by thermal annealing. We show that the nature of gate dielectrics plays an important role in soldered CdSe NC FETs. The capacitance of dielectrics and the NC electronic structure near gate dielectric affect the distribution of localized traps and trap filling, determining carrier mobility and operational stability of the NC FETs. We expand the application of the NC soldering process to core-shell NCs consisting of a III-V InAs core and a CdSe shell with composition-matched [Cd2Se3](2-) molecular solders. Soldering CdSe shells forms nanoheterostructured material that combines high electron mobility and near-IR photoresponse.

Wetting properties of Au/Sn solders for microelectronics

NASA Astrophysics Data System (ADS)

Peterson, K. A.; Williams, C. B.

Hermetic sealing of microelectronic packages with Au/Sn solder is critically dependent upon good wetting. In studying specific problems in hermetic sealing, a solderability test based on ASTM standard F-357-78 has proven useful. The test has helped isolate and quantify the effects of contamination due to epoxy die attach and related handling, thermal preconditioning of packages, gold plating thickness, time and temperature during sealing, and solder alloy composition as they affect wetting. Some differences in hardware have been documented between manufacturing lots, but the overriding factors have been contamination which occurs during packaging process flows and thermal preconditioning during processing. The paper includes a review of metallurgical aspects of soldering to a non-inert surface and an examination of microstructural differences in seal joints. The results also quantify the conventional wisdom that alloys which are on the tin-rich side of the eutectic composition offer superior wetting properties.

Soldering and brazing safety guide: A handbook on space practice for those involved in soldering and brazing

NASA Astrophysics Data System (ADS)

This manual provides those involved in welding and brazing with effective safety procedures for use in performance of their jobs. Hazards exist in four types of general soldering and brazing processes: (1) cleaning; (2) application of flux; (3) application of heat and filler metal; and (4) residue cleaning. Most hazards during those operations can be avoided by using care, proper ventilation, protective clothing and equipment. Specific process hazards for various methods of brazing and soldering are treated. Methods to check ventilation are presented as well as a check of personal hygiene and good maintenance practices are stressed. Several emergency first aid treatments are described.

Experimental Methods in Reduced-gravity Soldering Research

NASA Technical Reports Server (NTRS)

Pettegrew, Richard D.; Struk, Peter M.; Watson, John K.; Haylett, Daniel R.

2002-01-01

The National Center for Microgravity Research, NASA Glenn Research Center, and NASA Johnson Space Center are conducting an experimental program to explore the influence of reduced gravity environments on the soldering process. An improved understanding of the effects of the acceleration environment is important to application of soldering during current and future human space missions. Solder joint characteristics that are being considered include solder fillet geometry, porosity, and microstructural features. Both through-hole and surface mounted devices are being investigated. This paper focuses on the experimental methodology employed in this project and the results of macroscopic sample examination. The specific soldering process, sample configurations, materials, and equipment were selected to be consistent with those currently on-orbit. Other apparatus was incorporated to meet requirements imposed by operation onboard NASA's KC-135 research aircraft and instrumentation was provided to monitor both the atmospheric and acceleration environments. The contingent of test operators was selected to include both highly skilled technicians and less skilled individuals to provide a population cross-section that would be representative of the skill mix that might be encountered in space mission crews.

Around Marshall

NASA Image and Video Library

1983-08-10

One of the main components of the Hubble Space Telescope (HST) is the Solar Array Drive Electronics (SADE) system. This system interfaces with the Support System Module (SSM) for exchange of operational commands and telemetry data. SADE operates and controls the Solar Array Drive Mechanisms (SADM) for the orientation of the Solar Array Drive (SAD). It also monitors the position of the arrays and the temperature of the SADM. During the first HST servicing mission, the astronauts replaced the SADE component because of some malfunctions. This turned out to be a very challenging extravehicular activity (EVA). Two transistors and two diodes had been thermally stressed with the conformal coating discolored and charred. Soldered cornections became molten and reflowed between the two diodes. The failed transistors gave no indication of defective construction. All repairs were made and the HST was redeposited into orbit. Prior to undertaking this challenging mission, the orbiter's crew trained at Marshall Space Flight Center's (MSFC) Neutral Buoyancy Simulator (NBS) to prepare themselves for working in a low gravity environment. They also practiced replacing HST parts and exercised maneuverability and equipment handling. Pictured is an astronaut practicing climbing a space platform that was necessary in making repairs on the HST.

Neutral Buoyancy Simulator - SADE NBS Test

NASA Technical Reports Server (NTRS)

1983-01-01

One of the main components of the Hubble Space Telescope (HST) is the Solar Array Drive Electronics (SADE) system. This system interfaces with the Support System Module (SSM) for exchange of operational commands and telemetry data. SADE operates and controls the Solar Array Drive Mechanisms (SADM) for the orientation of the Solar Array Drive (SAD). It also monitors the position of the arrays and the temperature of the SADM. During the first HST servicing mission, the astronauts replaced the SADE component because of some malfunctions. This turned out to be a very challenging extravehicular activity (EVA). Two transistors and two diodes had been thermally stressed with the conformal coating discolored and charred. Soldered cornections became molten and reflowed between the two diodes. The failed transistors gave no indication of defective construction. All repairs were made and the HST was redeposited into orbit. Prior to undertaking this challenging mission, the orbiter's crew trained at Marshall Space Flight Center's (MSFC) Neutral Buoyancy Simulator (NBS) to prepare themselves for working in a low gravity environment. They also practiced replacing HST parts and exercised maneuverability and equipment handling. Pictured is an astronaut practicing climbing a space platform that was necessary in making repairs on the HST.

Neutral Buoyancy Simulator-NB50B-SADE Training Exercises

NASA Technical Reports Server (NTRS)

1983-01-01

One of the main components of the Hubble Space Telescope (HST) is the Solar Array Drive Electronics (SADE) system. This system interfaces with the Support System Module (SSM) for exchange of operational commands and telemetry data. SADE operates and controls the Solar Array Drive Mechanisms (SADM) for the orientation of the Solar Array Drive (SAD). It also monitors the position of the arrays and the temperature of the SADM. During the first HST servicing mission, the astronauts replaced the SADE component because of some malfunctions. This turned out to be a very challenging extravehicular activity (EVA). Two transistors and two diodes had been thermally stressed with the conformal coating discolored and charred. Soldered cornections became molten and reflowed between the two diodes. The failed transistors gave no indication of defective construction. All repairs were made and the HST was redeposited into orbit. Prior to undertaking this challenging mission, the orbiter's crew trained at Marshall Space Flight Center's (MSFC) Neutral Buoyancy Simulator (NBS) to prepare themselves for working in a low gravity environment. They also practiced replacing HST parts and exercised maneuverability and equipment handling. Pictured are crew members practicing on a space platform.

Robust solder joint attachment of coaxial cable leads to piezoelectric ceramic electrodes.

PubMed

Vianco, P T

1993-01-01

A technique was developed for the solder attachment of coaxial cable leads to silver-bearing thick-film electrodes on piezoelectric ceramics. Soldering the cable leads directly to the thick film caused bonds with low mechanical strength due to poor solder joint geometry. A barrier coating of 1.5 mum Cu/1.5 mum Ni/1.0 mum Sn deposited on the thick-film layer improved the strength of the solder joints by eliminating the adsorption of Ag from the thick film, which was responsible for the improper solder joint geometry. The procedure does not require special preparation of the electrode surface and is cost effective due to the use of nonprecious metal films and the batch processing capabilities of the electron beam deposition technique.

Thermal Cycling Fatigue in DIPs Mounted with Eutectic Tin-Lead Solder Joints in Stub and Gullwing Geometries

NASA Technical Reports Server (NTRS)

Winslow, J. W.; Silveira, C. de

1993-01-01

It has long been known that solder joints under mechanical stress are subject to failure. In early electronic systems, such failures were avoided primarily by avoiding the use of solder as a mechanical structural component. The rule was first to make sound wire connections that did not depend mechanically on solder, and only then to solder them. Careful design and miniaturization in modern electronic systems limits the mechanical stresses exerted on solder joints to values less than their yield points, and these joints have become integral parts of the mechanical structures. Unfortunately, while these joints are strong enough when new, they have proven vulnerable to fatigue failures as they age. Details of the fatigue process are poorly understood, making predictions of expected lifetimes difficult.

Soldering of Carbon Materials Using Transition Metal Rich Alloys.

PubMed

Burda, Marek; Lekawa-Raus, Agnieszka; Gruszczyk, Andrzej; Koziol, Krzysztof K K

2015-08-25

Joining of carbon materials via soldering has not been possible up to now due to lack of wetting of carbons by metals at standard soldering temperatures. This issue has been a severely restricting factor for many potential electrical/electronic and mechanical applications of nanostructured and conventional carbon materials. Here we demonstrate the formation of alloys that enable soldering of these structures. By addition of several percent (2.5-5%) of transition metal such as chromium or nickel to a standard lead-free soldering tin based alloy we obtained a solder that can be applied using a commercial soldering iron at typical soldering temperatures of approximately 350 °C and at ambient conditions. The use of this solder enables the formation of mechanically strong and electrically conductive joints between carbon materials and, when supported by a simple two-step technique, can successfully bond carbon structures to any metal terminal. It has been shown using optical and scanning electron microscope images as well as X-ray diffraction patterns and energy dispersive X-ray mapping that the successful formation of carbon-solder bonds is possible, first, thanks to the uniform nonreactive dispersion of transition metals in the tin-based matrix. Further, during the soldering process, these free elements diffuse into the carbon-alloy border with no formation of brazing-like carbides, which would damage the surface of the carbon materials.

Soldering Tested in Reduced Gravity

NASA Technical Reports Server (NTRS)

Struk, Peter M.; Pettegrew, Richard D.; Watson, J. Kevin; Down, Robert S.; Haylett, Daniel R.

2005-01-01

Whether used occasionally for contingency repair or routinely in nominal repair operations, soldering will become increasingly important to the success of future long-duration human space missions. As a result, it will be critical to have a thorough understanding of the service characteristics of solder joints produced in reduced-gravity environments. The National Center for Space Exploration Research (via the Research for Design program), the NASA Glenn Research Center, and the NASA Johnson Space Center are conducting an experimental program to explore the influence of reduced gravity environments on the soldering process. Solder joint characteristics that are being considered include solder fillet geometry, porosity, and microstructural features. Both through-hole (see the drawing and image on the preceding figure) and surface-mounted devices are being investigated. This effort (the low-gravity portion being conducted on NASA s KC-135 research aircraft) uses the soldering hardware currently available on the International Space Station. The experiment involves manual soldering by a contingent of test operators, including both highly skilled technicians and less skilled individuals to provide a skill mix that might be encountered in space mission crews. The experiment uses both flux-cored solder and solid-core solder with an externally applied flux. Other experimental parameters include the type of flux, gravitational level (nominally zero,

Abrupt reflow enhances cytokine-induced proinflammatory activation of endothelial cells during simulated shock and resuscitation.

PubMed

Li, Ranran; Zijlstra, Jan G; Kamps, Jan A A M; van Meurs, Matijs; Molema, Grietje

2014-10-01

Circulatory shock and resuscitation are associated with systemic hemodynamic changes, which may contribute to the development of MODS (multiple organ dysfunction syndrome). In this study, we used an in vitro flow system to simulate the consecutive changes in blood flow as occurring during hemorrhagic shock and resuscitation in vivo. We examined the kinetic responses of different endothelial genes in human umbilical vein endothelial cells preconditioned to 20 dyne/cm unidirectional laminar shear stress for 48 h to flow cessation and abrupt reflow, respectively, as well as the effect of flow cessation and reflow on tumor necrosis factor-α (TNF-α)-induced endothelial proinflammatory activation. Endothelial CD31 and VE-cadherin were not affected by the changes in flow in the absence or presence of TNF-α. The messenger RNA levels of proinflammatory molecules E-selectin, VCAM-1 (vascular cell adhesion molecule 1), and IL-8 (interleukin 8) were significantly induced by flow cessation respectively acute reflow, whereas ICAM-1 (intercellular adhesion molecule 1) was downregulated on flow cessation and induced by subsequent acute reflow. Flow cessation also affected the Ang/Tie2 (Angiopoietin/Tie2 receptor tyrosine kinase) system by downregulating Tie2 and inducing its endothelial ligand Ang2, an effect that was further extended on acute reflow. Furthermore, the induction of proinflammatory adhesion molecules by TNF-α under flow cessation was significantly enhanced on subsequent acute reflow. This study demonstrated that flow alterations per se during shock and resuscitation contribute to endothelial activation and that these alterations interact with proinflammatory factors coexisting in vivo such as TNF-α. The abrupt reflow-related enhancement of cytokine-induced endothelial proinflammatory activation supports the concept that sudden regain of flow during resuscitation has an aggravating effect on endothelial activation, which may play a significant role in vascular dysfunction and consequent organ injury. This study implies that the improvement of resuscitation strategies and the pharmacological interference with proinflammatory signaling cascades at the right time of resuscitation of shock patients may be beneficial to regain and/or maintain organ function in patients after circulatory shock.

The failure analysis and lifetime prediction for the solder joint of the magnetic head

NASA Astrophysics Data System (ADS)

Xiao, Xianghui; Peng, Minfang; Cardoso, Jaime S.; Tang, Rongjun; Zhou, YingLiang

2015-02-01

Micro-solder joint (MSJ) lifetime prediction methodology and failure analysis (FA) are to assess reliability by fatigue model with a series of theoretical calculations, numerical simulation and experimental method. Due to shortened time of solder joints on high-temperature, high-frequency sampling error that is not allowed in productions may exist in various models, including round-off error. Combining intermetallic compound (IMC) growth theory and the FA technology for the magnetic head in actual production, this thesis puts forward a new growth model to predict life expectancy for solder joint of the magnetic head. And the impact of IMC, generating from interface reaction between slider (magnetic head, usually be called slider) and bonding pad, on mechanical performance during aging process is analyzed in it. By further researching on FA of solder ball bonding, thesis chooses AuSn4 growth model that affects least to solder joint mechanical property to indicate that the IMC methodology is suitable to forecast the solder lifetime. And the diffusion constant under work condition 60 °C is 0.015354; the solder lifetime t is 14.46 years.

Evaluating print performance of Sn-Ag-Cu lead-free solder pastes used in electronics assembly process

NASA Astrophysics Data System (ADS)

Mallik, S.; Bauer, R.; Hübner, F.; Ekere, N. N.

2011-01-01

Solder paste is the most widely used interconnection material in the electronic assembly process for attaching electronic components/devices directly onto the surface of printed circuit boards, using stencil printing process. This paper evaluates the performance of three different commercially available Sn-Ag-Cu solder pastes formulated with different particle size distributions (PSD), metal content and alloy composition. A series of stencil printing tests were carried out using a specially designed stencil of 75 μm thickness and apertures of 300×300 μm2 dimension and 500 μm pitch sizes. Solder paste printing behaviors were found related to attributes such as slumping and surface tension and printing performance was correlated with metal content and PSD. The results of the study should benefit paste manufacturers and SMT assemblers to improve their products and practices.

Thermodynamic Description of the Quaternary Ag-Bi-Cu-Sn System

NASA Astrophysics Data System (ADS)

Gierlotka, Wojciech

2018-01-01

Lead-free soldering is an important part of electronic devices production. New lead-free solders that replace classical Sn-37Pb solder are still under development. Thermodynamic modeling makes the development process faster, cheaper and more environmentally friendly due to predictions of phases stabilities and phases transformations. In this work, the thermodynamic description of quaternary Ag-Bi-Cu-Sn system is presented. The thermodynamic assessment of promising lead-free quaternary solder was prepared using the Calphad approach. A good agreement between available experimental data and calculation was found.

Subgrain Rotation Behavior in Sn3.0Ag0.5Cu-Sn37Pb Solder Joints During Thermal Shock

NASA Astrophysics Data System (ADS)

Han, Jing; Tan, Shihai; Guo, Fu

2018-01-01

Ball grid array (BGA) samples were soldered on a printed circuit board with Sn37Pb solder paste to investigate the recrystallization induced by subgrain rotation during thermal shock. The composition of the solder balls was Sn3.0Ag0.5Cu-Sn37Pb, which comprised mixed solder joints. The BGA component was cross-sectioned before thermal shock. The microstructure and grain orientations were obtained by a scanning electron microscope equipped with an electron back-scattered diffraction system. Two mixed solder joints at corners of the BGA component were selected as the subjects. The results showed that recrystallization occurred at the corner of the solder joints after 200 thermal shock cycles. The recrystallized subgrains had various new grain orientations. The newly generated grain orientations were closely related to the initial grain orientations, which indicated that different subgrain rotation behaviors could occur in one mixed solder joint with the same initial grain orientation. When the misorientation angles were very small, the rotation axes were about Sn [100], [010] and [001], as shown by analyzing the misorientation angles and subgrain rotation axes, while the subgrain rotation behavior with large misorientation angles in the solder joints was much more complicated. As Pb was contained in the solder joints and the stress was concentrated on the corner of the mixed solder joints, concaves and cracks were formed. When the adjacent recrystallized subgrains were separated, and the process of the continuous recrystallization was limited.

Microstructure characteristics of vacuum glazing brazing joints using laser sealing technique

NASA Astrophysics Data System (ADS)

Liu, Sixing; Yang, Zheng; Zhang, Jianfeng; Zhang, Shanwen; Miao, Hong; Zhang, Yanjun; Zhang, Qi

2018-05-01

Two pieces of plate glass were brazed into a composite of glazing with a vacuum chamber using PbO-TiO2-SiO2-RxOy powder filler alloys to develop a new type of vacuum glazing. The brazing process was carried out by laser technology. The interface characteristics of laser brazed joints formed between plate glass and solder were investigated using optical microscope, scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS) and X-ray diffraction (XRD) techniques. The results show that the inter-diffusion of Pb/Ti/Si/O elements from the sealing solder toward the glass and O/Al/Si elements from the glass toward the solder, resulting in a reaction layer in the brazed joints. The microstructure phases of PbTiO3, AlSiO, SiO2 and PbO in the glass/solder interface were confirmed by XRD analysis. The joining of the sealing solder to the glass was realized by the reaction products like fibrous structures on interface, where the wetting layer can help improve the bonding performance and strength between the sealing solder and the plate glass during the laser brazing process.

Derivation of mechanical characteristics for Ni/Au intermetallic surface with SAC305 solder

NASA Astrophysics Data System (ADS)

Kim, Jong-Min; Lee, Hyun-Boo; Chang, Yoon-Suk; Choi, Jae-Boong

2013-03-01

Many surface finish methods are used to connect a substrate with the electric components of IT products in the micro-packaging process, and various types of lead-free solder have been developed as alternative materials to lead-based solder to reduce environmental contamination. However, there has been little research on the mechanical properties of the inter-metallic surface which is generated in the bumping process between the lead-free solder and surface films such as Ni/Au. The present work is to derive the material properties of a Ni/Au inter-metallic surface with SAC305 solder. A series of indentation tests were carried out by changing four nano-scale indentation depths and two strain rates. Also, a reverse algorithm method was adopted to determine the elastic-plastic stress-strain curve based on the load-displacement curve from the indentation test data. As a result of the material characterization effort, the mean elastic modulus, yield strength and strain hardening exponent of IMC with Ni/Au finish were determined.

Fabrication of microlens array and bifocal microlens using the methods of laser ablation and solvent reflow

NASA Astrophysics Data System (ADS)

Yu, Cheng-Chian; Ho, Jeng-Rong

2015-12-01

Based on the techniques of laser microdrilling and solvent reflow, this study reports on a straightforward approach for fabricating plastic microlens arrays (MLAs). First, we use the ArF excimer laser to drill microholes on a polymethylmethacrylate plate for defining the lens number, initial depth, and diameter. The propylene glycol monomethyl ether acetate solvent is then employed to regulate the surface profile that leads to a resulting negative (concave) MLA. The corresponding positive (convex), polydimethyl-siloxane MLA is obtained by the soft-replica-molding technique. Through varying the pattern size and period on the mask and the light intensity for laser drilling and regulating the solvent in the reflow process, we exhibit the feasibility of making MLAs with various sizes and shapes. By modifying the laser ablation step to drill two microholes with different diameters and depths at two levels, we fabricate a bifocal microlens. The obtained microlenses have excellent surface and optical properties: surface roughness down to several nanometers and focal lengths varying from hundreds to thousands of micrometers. This approach is flexible for constructing microlenses with various sizes and shapes and can fabricate MLAs with a high fill factor.

Method and apparatus for jetting, manufacturing and attaching uniform solder balls

DOEpatents

Yost, F.G.; Frear, D.R.; Schmale, D.T.

1999-01-05

An apparatus and process are disclosed for jetting molten solder in the form of balls directly onto all the metallized interconnects lands for a ball grid array package in one step with no solder paste required. Molten solder is jetted out of a grid of holes using a piston attached to a piezoelectric crystal. When voltage is applied to the crystal it expands forcing the piston to extrude a desired volume of solder through holes in the aperture plate. When the voltage is decreased the piston reverses motion creating an instability in the molten solder at the aperture plate surface and thereby forming spherical solder balls that fall onto a metallized substrate. The molten solder balls land on the substrate and form a metallurgical bond with the metallized lands. The size of the solder balls is determined by a combination of the size of the holes in the aperture plate, the duration of the piston pulse, and the displacement of the piston. The layout of the balls is dictated by the location of the hooks in the grid. Changes in ball size and layout can be easily accomplished by changing the grid plate. This invention also allows simple preparation of uniform balls for subsequent supply to BGA users. 7 figs.

Method and apparatus for jetting, manufacturing and attaching uniform solder balls

DOEpatents

Yost, Frederick G.; Frear, Darrel R.; Schmale, David T.

1999-01-01

An apparatus and process for jetting molten solder in the form of balls directly onto all the metallized interconnects lands for a ball grid array package in one step with no solder paste required. Molten solder is jetted out of a grid of holes using a piston attached to a piezoelectric crystal. When voltage is applied to the crystal it expands forcing the piston to extrude a desired volume of solder through holes in the aperture plate. When the voltage is decreased the piston reverses motion creating an instability in the molten solder at the aperture plate surface and thereby forming spherical solder balls that fall onto a metallized substrate. The molten solder balls land on the substrate and form a metallurgical bond with the metallized lands. The size of the solder balls is determined by a combination of the size of the holes in the aperture plate, the duration of the piston pulse, and the displacement of the piston. The layout of the balls is dictated by the location of the hooks in the grid. Changes in ball size and layout can be easily accomplished by changing the grid plate. This invention also allows simple preparation of uniform balls for subsequent supply to BGA users.

Intelligent laser soldering inspection and process control

NASA Technical Reports Server (NTRS)

Vanzetti, Riccardo

1987-01-01

Component assembly on printed circuitry keeps making giant strides toward denser packaging and smaller dimensions. From a single layer to multilayer, from through holes to surface mounted components and tape applied bonds, unrelenting progress results in new, difficult problems in assembling, soldering, inspecting and controlling the manufacturing process of the new electronics. Among the major problems are the variables introduced by human operators. The small dimensions and the tight assembly tolerances are now successfully met by machines which are faster and more precise than the human hand. The same is true for soldering. But visual inspection of the solder joints is now so severely limited by the ever shrinking area accessible to the human eye that the inspector's diagnosis cannot be trusted any longer. Solutions to correcting these problems are discussed.

The 'MAP strategy' (Maximum aspiration of atherothrombus and adjunctive glycoprotein IIb/IIIa inhibitor utilization combined with prolonged inflation of balloon/stent) for preventing no-reflow in patients with ST-segment elevation myocardial infarction undergoing percutaneous coronary intervention: A retrospective analysis of seventy-one cases.

PubMed

Potdar, Anil; Sharma, Satyavan

2015-12-01

'No-reflow' phenomenon is a common occurrence in percutaneous coronary intervention (PCI). A three-component 'MAP strategy' was designed to prevent no-reflow by addressing both intralesional and intraluminal thrombus in patients with ST-segment elevation myocardial infarction (STEMI). In this analysis, we observed Thrombolysis In Myocardial Infarction (TIMI) flow grade 3 or 2 in all patients, with no incidence of no-reflow. Myocardial blush grade (MBG) 3 or 2 was observed in most (87.32%) patients. Left ventricular ejection fraction (LVEF) was improved, without any incidence of death up to 9-month follow-up. All patients safely tolerated the strategy-driven prolonged, 35-s inflation of the balloon/stent. Copyright © 2016. Published by Elsevier B.V.

Thermomechanical fatigue life prediction for several solders

NASA Astrophysics Data System (ADS)

Wen, Shengmin

Since solder connections operate at high homologous temperature, solders are high temperature materials. This feature makes their mechanical behavior and fatigue phenomena unique. Based on experimental findings, a physical damage mechanism is introduced for solders. The mechanism views the damage process as a series of independent local damage events characterized by the failure of individual grains, while the structural damage is the eventual percolation result of such local events. Fine's dislocation energy density concept and Mura's microcrack initiation theory are adopted to derive the fatigue formula for an individual grain. A physical damage metric is introduced to describe the material with damage. A unified creep and plasticity constitutive model is adopted to simulate the mechanical behavior of solders. The model is cast into a continuum damage mechanics framework to simulate material with damage. The model gives good agreement with the experimental results of 96.5Pb-3.5Sn and 96.5Sn-3.5Ag solders under uniaxial strain-controlled cyclic loading. The model is convenient for implementation into commercial computational packages. Also presented is a fatigue theory with its failure criterion for solders based on physical damage mechanism. By introducing grain orientation into the fatigue formula, an m-N curve (m is Schmid factor) at constant loading condition is suggested for fatigue of grains with different orientations. A solder structure is defined as fatigued when the damage metric reaches a critical threshold, since at this threshold the failed grains may form a cluster and percolate through the structure according to percolation theory. Fatigue data of 96.5Pb-3.5Sn solder bulk specimens under various uniaxial tension tests were analyzed. Results show that the theory gives consistent predictions under broad conditions, while inelastic strain theory does not. The theory is anisotropic with no size limitation to its application, which could be suitable for anisotropic small-scale (micron or nano scale) solder joints. More importantly, the theory is materials science based so that the parameters of the fatigue formula can be worked out by testing of bulk specimens while the formula can be applicable to small-scale structures. The theory suggests metallurgical control in the manufacturing process to optimize the fatigue life of solder structures.

Characteristics of solder joints under fatigue loads using piezomechanical actuation

NASA Astrophysics Data System (ADS)

Shim, Dong-Jin; Spearing, S. Mark

2003-07-01

Crack initiation and growth characteristics of solder joints under fatigue loads are investigated using piezomechanical actuation. Cracks in solder joints, which can cause failure in microelectronics components, are induced via piezoelectricity in piezo-ceramic bonded joints. Lead-zirconate-titanate ceramic plates and eutectic Sn-Pb solder bonded in a double-lap shear configuration are used in the investigation. Electric field across each piezo-ceramic plate is applied such that shear stresses/strains are induced in the solder joints. The experiments show that cracks initiate in the solder joints around defects such as voids and grow in length until they coalesce with other cracks from adjacent voids. These observations are compared with the similar thermal cycling tests from the literature to show feasibility and validity of the current method in investigating the fatigue characteristics of solder joints. In some specimens, cracks in the piezo-ceramic plates are observed, and failure in the specimens generally occurred due to piezo-ceramic plate fracture. The issues encountered in implementing this methodology such as low actuation and high processing temperatures are further discussed.

Copper/solder intermetallic growth studies.

PubMed

Kirchner, K W; Lucey, G K; Geis, J

1993-08-01

Copper samples, hot solder (eutectic) dipped and thermally aged, were cross-sectioned and placed in an environmental scanning electronic microscope (ESEM). While in the ESEM the samples were heated for approximately 2.5 h at 170 degrees C to stimulate the growth of additional Cu/Sn intermetallic compound. The intent of the study was to obtain a continuous real-time videotape record of the diffusion process and compare the observations to static SEM images reported to represent long-term, naturally aged intermetallic growth. The video obtained allows the observation of the diffusion process and relativistic growth phenomena at the Cu, Cu3Sn, Cu6Sn5, and solder interfaces as well as effects on the bulk Cu and solder. Effects contrary to earlier reports were observed; for example, growth rates of Cu3Sn were found to greatly exceed those of Cu6Sn5.

The In-Space Soldering Investigation: Research Conducted on the International Space Station in Support of NASA's Exploration Initiative

NASA Technical Reports Server (NTRS)

Grugel, R. N.; Fincke, M.; Sergre, P. N.; Ogle, J. A.; Funkhouser, G.; Parris, F.; Murphy, L.; Gillies, D.; Hua, F.

2004-01-01

Soldering is a well established joining and repair process that is of particular importance in the electronics industry. Still. internal solder joint defects such as porosity are prevalent and compromise desired properties such as electrical/thermal conductivity and fatigue strength. Soldering equipment resides aboard the International Space Station (ISS) and will likely accompany Exploration Missions during transit to, as well as on, the moon and Mars. Unfortunately, detrimental porosity appears to be enhanced in lower gravity environments. To this end, the In-Space Soldering Investigation (ISSI) is being conducted in the Microgravity Workbench Area (MWA) aboard the ISS as "Saturday Science" with the goal of promoting our understanding of joining techniques, shape equilibrium, wetting phenomena, and microstructural development in a microgravity environment. The work presented here will focus on direct observation of melting dynamics and shape determination in comparison to ground-based samples, with implications made to processing in other low-gravity environments. Unexpected convection effects, masked on Earth, will also be shown as well as the value of the ISS as a research platform in support of Exploration Missions.

The In-Space Soldering Investigation: To Date Analysis of Experiments Conducted on the International Space Station

NASA Technical Reports Server (NTRS)

Grugel, Richard N.; Gillies, D. C.; Hua, F.; Anilkumar, A.

2006-01-01

Soldering is a well established joining and repair process that is of particular importance in the electronics industry. Still, internal solder joint defects such as porosity are prevalent and compromise desired properties such as electrical/thermal conductivity and fatigue strength. Soldering equipment resides aboard the International Space Station (ISS) and will likely accompany Exploration Missions during transit to, as well as on, the moon and Mars. Unfortunately, detrimental porosity appears to be enhanced in lower gravity environments. To this end, the In-Space Soldering Investigation (ISSI) is being conducted in the Microgravity Workbench Area (MWA) aboard the ISS as "Saturday Science" with the goal of promoting our understanding of joining techniques, shape equilibrium, wetting phenomena, and microstructural development in a microgravity environment. The work presented here will focus on direct observation of melting dynamics and shape determination in comparison to ground-based samples, with implications made to processing in other low-gravity environments. Unexpected convection effects, masked on Earth, will also be shown as well as the value of the ISS as a research platform in support of Exploration Missions.

Delayed treatment with hypothermia protects against the no-reflow phenomenon despite failure to reduce infarct size.

PubMed

Hale, Sharon L; Herring, Michael J; Kloner, Robert A

2013-01-04

Many studies have shown that when hypothermia is started after coronary artery reperfusion (CAR), it is ineffective at reducing necrosis. However, some suggest that hypothermia may preferentially reduce no-reflow. Our aim was to test the effects of hypothermia on no-reflow when initiated close to reperfusion and 30 minutes after reperfusion, times not associated with a protective effect on myocardial infarct size. Rabbits received 30 minutes coronary artery occlusion/3 hours CAR. In protocol 1, hearts were treated for 1 hour with topical hypothermia (myocardial temperature ≈32°C) initiated at 5 minutes before or 5 minutes after CAR, and the results were compared with a normothermic group. In protocol 2, hypothermia was delayed until 30 minutes after CAR and control hearts remained normothermic. In protocol 1, risk zones were similar and infarct size was not significantly reduced by hypothermia initiated close to CAR. However, the no-reflow defect was significantly reduced by 43% (5 minutes before CAR) and 38% (5 minutes after CAR) in hypothermic compared with normothermic hearts (P=0.004, ANOVA, P=ns between the 2 treated groups). In protocol 2, risk zones and infarct sizes were similar, but delayed hypothermia significantly reduced no-reflow in hypothermic hearts by 30% (55±6% of the necrotic region in hypothermia group versus 79±6% with normothermia, P=0.008). These studies suggest that treatment with hypothermia reduces no-reflow even when initiated too late to reduce infarct size and that the microvasculature is especially receptive to the protective properties of hypothermia and confirm that microvascular damage is in large part a form of true reperfusion injury.

A novel method for direct solder bump pull testing using lead-free solders

NASA Astrophysics Data System (ADS)

Turner, Gregory Alan

This thesis focuses on the design, fabrication, and evaluation of a new method for testing the adhesion strength of lead-free solders, named the Isotraction Bump Pull method (IBP). In order to develop a direct solder joint-strength testing method that did not require customization for different solder types, bump sizes, specific equipment, or trial-and-error, a combination of two widely used and accepted standards was created. First, solder bumps were made from three types of lead free solder were generated on untreated copper PCB substrates using an in-house fabricated solder bump-on-demand generator, Following this, the newly developed method made use of a polymer epoxy to encapsulate the solder bumps that could then be tested under tension using a high precision universal vertical load machine. The tests produced repeatable and predictable results for each of the three alloys tested that were in agreement with the relative behavior of the same alloys using other testing methods in the literature. The median peak stress at failure for the three solders tested were 2020.52 psi, 940.57 psi, and 2781.0 psi, and were within one standard deviation of the of all data collected for each solder. The assumptions in this work that brittle fracture occurred through the Intermetallic Compound layer (IMC) were validated with the use of Energy-Dispersive X-Ray Spectrometry and high magnification of the fractured surface of both newly exposed sides of the test specimens. Following this, an examination of the process to apply the results from the tensile tests into standard material science equations for the fracture of the systems was performed..

Detection of micro solder balls using active thermography and probabilistic neural network

NASA Astrophysics Data System (ADS)

He, Zhenzhi; Wei, Li; Shao, Minghui; Lu, Xingning

2017-03-01

Micro solder ball/bump has been widely used in electronic packaging. It has been challenging to inspect these structures as the solder balls/bumps are often embedded between the component and substrates, especially in flip-chip packaging. In this paper, a detection method for micro solder ball/bump based on the active thermography and the probabilistic neural network is investigated. A VH680 infrared imager is used to capture the thermal image of the test vehicle, SFA10 packages. The temperature curves are processed using moving average technique to remove the peak noise. And the principal component analysis (PCA) is adopted to reconstruct the thermal images. The missed solder balls can be recognized explicitly in the second principal component image. Probabilistic neural network (PNN) is then established to identify the defective bump intelligently. The hot spots corresponding to the solder balls are segmented from the PCA reconstructed image, and statistic parameters are calculated. To characterize the thermal properties of solder bump quantitatively, three representative features are selected and used as the input vector in PNN clustering. The results show that the actual outputs and the expected outputs are consistent in identification of the missed solder balls, and all the bumps were recognized accurately, which demonstrates the viability of the PNN in effective defect inspection in high-density microelectronic packaging.

Solder creep-fatigue interactions with flexible leaded parts

NASA Technical Reports Server (NTRS)

Ross, R. G., Jr.; Wen, L. C.; Mon, G. R.; Jetter, E.

1992-01-01

With flexible leaded parts, the solder-joint failure process involves a complex interplay of creep and fatigue mechanisms. To better understand the role of creep in typical multi-hour cyclic loading conditions, a specialized non-linear finite-element creep simulation computer program has been formulated. The numerical algorithm includes the complete part-lead-solder-PWB system, accounting for strain-rate dependence of creep on applied stress and temperature, and the role of the part-lead dimensions and flexibility that determine the total creep deflection (solder strain range) during stress relaxation. The computer program has been used to explore the effects of various solder creep-fatigue parameters such as lead height and stiffness, thermal-cycle test profile, and part/board differential thermal expansion properties. One of the most interesting findings is the strong presence of unidirectional creep-ratcheting that occurs during thermal cycling due to temperature dominated strain-rate effects. To corroborate the solder fatigue model predictions, a number of carefully controlled thermal-cycle tests have been conducted using special bimetallic test boards.

Mechanical Deformation Behavior of Sn-Ag-Cu Solders with Minor Addition of 0.05 wt.% Ni

NASA Astrophysics Data System (ADS)

Hammad, A. E.; El-Taher, A. M.

2014-11-01

The aim of the present work is to develop a comparative evaluation of the microstructural and mechanical deformation behavior of Sn-Ag-Cu (SAC) solders with the minor addition of 0.05 wt.% Ni. Test results showed that, by adding 0.05Ni element into SAC solders, generated mainly small rod-shaped (Cu,Ni)6Sn5 intermetallic compounds (IMCs) inside the β-Sn phase. Moreover, increasing the Ag content and adding Ni could result in the change of the shape and size of the IMC precipitate. Hence, a significant improvement is observed in the mechanical properties of SAC solders with increasing Ag content and Ni addition. On the other hand, the tensile results of Ni-doped SAC solders showed that both the yield stress and ultimate tensile strengths decrease with increasing temperature and with decreasing strain rate. This behavior was attributed to the competing effects of work hardening and dynamic recovery processes. The Sn-2.0Ag-0.5Cu-0.05Ni solder displayed the highest mechanical properties due to the formation of hard (Cu,Ni)6Sn5 IMCs. Based on the obtained stress exponents and activation energies, it is suggested that the dominant deformation mechanism in SAC (205)-, SAC (0505)- and SAC (0505)-0.05Ni solders is pipe diffusion, and lattice self-diffusion in SAC (205)-0.05Ni solder. In view of these results, the Sn-2.0Ag-0.5Cu-0.05Ni alloy is a more reliable solder alloy with improved properties compared with other solder alloys tested in the present work.

A Study on the Physical Properties and Interfacial Reactions with Cu Substrate of Rapidly Solidified Sn-3.5Ag Lead-Free Solder

NASA Astrophysics Data System (ADS)

Ma, Hai-Tao; Wang, Jie; Qu, Lin; Zhao, Ning; Kunwar, A.

2013-08-01

A rapidly solidified Sn-3.5Ag eutectic alloy produced by the melt-spinning technique was used as a sample in this research to investigate the microstructure, thermal properties, solder wettability, and inhibitory effect of Ag3Sn on Cu6Sn5 intermetallic compound (IMC). In addition, an as-cast Sn-3.5Ag solder was prepared as a reference. Rapidly solidified and as-cast Sn-3.5Ag alloys of the same size were soldered at 250°C for 1 s to observe their instant melting characteristics and for 3 s with different cooling methods to study the inhibitory effect of Ag3Sn on Cu6Sn5 IMC. Experimental techniques such as scanning electron microscopy, differential scanning calorimetry, and energy-dispersive spectrometry were used to observe and analyze the results of the study. It was found that rapidly solidified Sn-3.5Ag solder has more uniform microstructure, better wettability, and higher melting rate as compared with the as-cast material; Ag3Sn nanoparticles that formed in the rapidly solidified Sn-3.5Ag solder inhibited the growth of Cu6Sn5 IMC during aging significantly much strongly than in the as-cast material because their number in the rapidly solidified Sn-3.5Ag solder was greater than in the as-cast material with the same soldering process before aging. Among the various alternative lead-free solders, this study focused on comparison between rapidly solidified and as-cast solder alloys, with the former being observed to have better properties.

Ultrasonic semi-solid coating soldering 6061 aluminum alloys with Sn-Pb-Zn alloys.

PubMed

Yu, Xin-ye; Xing, Wen-qing; Ding, Min

2016-07-01

In this paper, 6061 aluminum alloys were soldered without a flux by the ultrasonic semi-solid coating soldering at a low temperature. According to the analyses, it could be obtained that the following results. The effect of ultrasound on the coating which promoted processes of metallurgical reaction between the components of the solder and 6061 aluminum alloys due to the thermal effect. Al2Zn3 was obtained near the interface. When the solder was in semi-solid state, the connection was completed. Ultimately, the interlayer mainly composed of three kinds of microstructure zones: α-Pb solid solution phases, β-Sn phases and Sn-Pb eutectic phases. The strength of the joints was improved significantly with the minimum shear strength approaching 101MPa. Copyright © 2016. Published by Elsevier B.V.

Al-Si-Cu/TiN multilayer interconnection and Al-Ge reflow sputtering technologies for quarter-micron devices

NASA Astrophysics Data System (ADS)

Kikkawa, Takamaro; Kikuta, Kuniko

1993-05-01

Issues of interconnection technologies for quarter-micron devices are the reliability of metal lines with quarter-micron feature sizes and the formation of contact-hole-plugs with high aspect ratios. This paper describes a TiN/Al-Si-Cu/TiN/Al-Si-Cu/TiN/Ti multilayer conductor structure as a quarter-micron interconnection technology and aluminum-germanium (Al-Ge) reflow sputtering as a contact-hole filling technology. The TiN/Al-Si-Cu/TiN/Al-Si-Cu/TiN/Ti multilayer conductor structure could suppress stress-induced voiding and improve the electromigration mean-time to failure. These improvements are attributed to the fact that the grain boundaries for the Al-Si-Cu film and the interfaces between the Al-Si-Cu and the TiN films are strengthened by the rigid intermetallic compound, TiAl3. The Al-Ge alloy reflow sputtering is a candidate for contact- and via-hole filling technologies in terms of reducing fabrication costs. The Al-Ge reflow sputtering achieved low temperature contact hole filling at 300 degree(s)C. Contact holes with a diameter of 0.25 micrometers and aspect ratio of 4 could be filled. This is attributed to the low eutectic temperature for Al-Ge (424 degree(s)C) and the effect of thin polysilicon underlayer on the enhancement of Al-Ge reflow.

Evaluation of Peripheral Blood Circulation Disorder in Scleroderma Patients Using an Optical Sensor with a Pressurization Mechanism

PubMed Central

Yamakoshi, Yoshiki

2016-01-01

Blood circulation function of peripheral blood vessels in skin dermis was evaluated employing an optical sensor with a pressurization mechanism using the blood outflow and reflow characteristics. The device contains a light source and an optical sensor. When applied to the skin surface, it first exerts the primary pressure (higher than the systolic blood pressure), causing an outflow of blood from the dermal peripheral blood vessels. After two heartbeats, the pressure is lowered (secondary pressure) and blood reflows into the peripheral blood vessels. Hemoglobin concentration, which changes during blood outflow and reflow, is derived from the received light intensity using the Beer–Lambert law. This method was evaluated in 26 healthy female volunteers and 26 female scleroderma patients. In order to evaluate the blood circulation function of the peripheral blood vessels of scleroderma patients, pressurization sequence which consists of primary pressure followed by secondary pressure was adopted. Blood reflow during the first heartbeat period after applying the secondary pressure of 40mmHg was (mean±SD) 0.059±0.05%mm for scleroderma patients and 0.173±0.104%mm for healthy volunteers. Blood reflow was significantly lower in scleroderma patients than in healthy volunteers (p<0.05). This result indicates that the information necessary for assessing blood circulation disorder of peripheral blood vessels in scleroderma patients is objectively obtained by the proposed method. PMID:27479094

Evaluation of Peripheral Blood Circulation Disorder in Scleroderma Patients Using an Optical Sensor with a Pressurization Mechanism.

PubMed

Yamakoshi, Yoshiki; Motegi, Sei-Ichiro; Ishikawa, Osamu

2016-01-01

Blood circulation function of peripheral blood vessels in skin dermis was evaluated employing an optical sensor with a pressurization mechanism using the blood outflow and reflow characteristics. The device contains a light source and an optical sensor. When applied to the skin surface, it first exerts the primary pressure (higher than the systolic blood pressure), causing an outflow of blood from the dermal peripheral blood vessels. After two heartbeats, the pressure is lowered (secondary pressure) and blood reflows into the peripheral blood vessels. Hemoglobin concentration, which changes during blood outflow and reflow, is derived from the received light intensity using the Beer-Lambert law. This method was evaluated in 26 healthy female volunteers and 26 female scleroderma patients. In order to evaluate the blood circulation function of the peripheral blood vessels of scleroderma patients, pressurization sequence which consists of primary pressure followed by secondary pressure was adopted. Blood reflow during the first heartbeat period after applying the secondary pressure of 40mmHg was (mean±SD) 0.059±0.05%mm for scleroderma patients and 0.173±0.104%mm for healthy volunteers. Blood reflow was significantly lower in scleroderma patients than in healthy volunteers (p<0.05). This result indicates that the information necessary for assessing blood circulation disorder of peripheral blood vessels in scleroderma patients is objectively obtained by the proposed method.

Stresses in Solder Joints of Electronic Packages

DTIC Science & Technology

1991-12-31

soldering process. The device is soldered to the circuit board at a temperature of +185zc and this tempature is assumed to propagate only to the lead wire...tri-material assembly, showing the notation used hereafter, is shown in Figure 7. The Suhir model is applicable to assemblies with continuous...therefore the radii of curvature of layers are all equal. Using equilibrium equation (7) and moment-curvature equation (9) yields ()D D Xp (x) D T() -m 3 x

Low-strain laser-based solder joining of mounted lenses

NASA Astrophysics Data System (ADS)

Burkhardt, Thomas; Hornaff, Marcel; Kamm, Andreas; Burkhardt, Diana; Schmidt, Erik; Beckert, Erik; Eberhardt, Ramona; Tünnermann, Andreas

2015-09-01

A novel laser-based soldering technique - Solderjet Bumping - using liquid solder droplets in a flux-free process with only localized heating is presented. We demonstrate an all inorganic, adhesive free bonding of optical components and support structures suitable for optical assemblies and instruments under harsh environmental conditions. Low strain bonding suitable for a following high-precision adjustment turning process is presented, addressing components and subsystems for objectives for high power and short wavelengths. The discussed case study shows large aperture transmissive optics (diameter approx. 74 mm and 50 mm) made of fused silica and LAK9G15, a radiation resistant glass, bonded to thermally matched metallic mounts. The process chain of Solderjet Bumping - cleaning, solderable metallization, handling, bonding and inspection - is discussed. This multi-material approach requires numerical modelling for dimensioning according to thermal and mechanical loads. The findings of numerical modelling, process parametrization and environmental testing (thermal and vibrational loads) are presented. Stress and strain introduced into optical components as well as deformation of optical surfaces can significantly deteriorate the wave front of passing light and therefore reduce system performance significantly. The optical performance with respect to stress/strain and surface deformation during bonding and environmental testing were evaluated using noncontact and nondestructive optical techniques: polarimetry and interferometry, respectively. Stress induced surface deformation of less than 100 nm and changes in optical path difference below 5 nm were achieved. Bond strengths of about 55 MPa are reported using tin-silver-copper soft solder alloy.

Interfacial reactions and compound formation of Sn-Ag-Cu solders by mechanical alloying on electroless Ni-P/Cu under bump metallization

NASA Astrophysics Data System (ADS)

Kao, Szu-Tsung; Duh, Jenq-Gong

2005-08-01

Electroless Ni-P under bump metallization (UBM) has been widely used in electronic interconnections due to the good diffusion barrier between Cu and solder. In this study, the mechanical alloying (MA) process was applied to produce the SnAgCu lead-free solder pastes. Solder joints after annealing at 240°C for 15 min were employed to investigate the evolution of interfacial reaction between electroless Ni-P/Cu UBM and SnAgCu solder with various Cu concentrations ranging from 0.2 to 1.0 wt.%. After detailed quantitative analysis with an electron probe microanalyzer, the effect of Cu content on the formation of intermetallic compounds (IMCs) at SnAgCu solder/electroless Ni-P interface was evaluated. When the Cu concentration in the solder was 0.2 wt.%, only one (Ni, Cu)3Sn4 layer was observed at the solder/electroless Ni-P interface. As the Cu content increased to 0.5 wt.%, (Cu, Ni)6Sn5 formed along with (Ni, Cu)3Sn4. However, only one (Cu, Ni)6Sn5 layer was revealed, if the Cu content was up to 1 wt.%. With the aid of microstructure evolution, quantitative analysis, and elemental distribution by x-ray color mapping, the presence of the Ni-Sn-P phase and P-rich layer was evidenced.

Thermal Cycling Life Prediction of Sn-3.0Ag-0.5Cu Solder Joint Using Type-I Censored Data

PubMed Central

Mi, Jinhua; Yang, Yuan-Jian; Huang, Hong-Zhong

2014-01-01

Because solder joint interconnections are the weaknesses of microelectronic packaging, their reliability has great influence on the reliability of the entire packaging structure. Based on an accelerated life test the reliability assessment and life prediction of lead-free solder joints using Weibull distribution are investigated. The type-I interval censored lifetime data were collected from a thermal cycling test, which was implemented on microelectronic packaging with lead-free ball grid array (BGA) and fine-pitch ball grid array (FBGA) interconnection structures. The number of cycles to failure of lead-free solder joints is predicted by using a modified Engelmaier fatigue life model and a type-I censored data processing method. Then, the Pan model is employed to calculate the acceleration factor of this test. A comparison of life predictions between the proposed method and the ones calculated directly by Matlab and Minitab is conducted to demonstrate the practicability and effectiveness of the proposed method. At last, failure analysis and microstructure evolution of lead-free solders are carried out to provide useful guidance for the regular maintenance, replacement of substructure, and subsequent processing of electronic products. PMID:25121138

Long-Term Effects of Soldering By-Products on Nickel-Coated Copper Wire

NASA Technical Reports Server (NTRS)

Rolin, T. D.; Hodge, R. E.

2008-01-01

An analysis of thirty-year-old, down graded flight cables was conducted to determine the makeup of a green material on the surface of the shielded wire near soldered areas and to ascertain if the green material had corroded the nickel-coated copper wire. Two likely candidates were possible due to the handling and environments to which these cables were exposed. The flux used to solder the cables is known to contain abietic acid, a carboxylic acid found in many pine rosins used for the soldering process. The resulting material copper abietate is green in color and is formed during the application of heat during soldering operations. Copper (II) chloride, which is also green in color is known to contaminate flight parts and is corrosive. Data is presented that shows the material is copper abietate, not copper (II) chloride, and more importantly that the abietate does not aggressively attack nickel-plated copper wire.

Homogeneous (Cu, Ni)6Sn5 intermetallic compound joints rapidly formed in asymmetrical Ni/Sn/Cu system using ultrasound-induced transient liquid phase soldering process.

PubMed

Li, Z L; Dong, H J; Song, X G; Zhao, H Y; Tian, H; Liu, J H; Feng, J C; Yan, J C

2018-04-01

Homogeneous (Cu, Ni) 6 Sn 5 intermetallic compound (IMC) joints were rapidly formed in asymmetrical Ni/Sn/Cu system by an ultrasound-induced transient liquid phase (TLP) soldering process. In the traditional TLP soldering process, the intermetallic joints formed in Ni/Sn/Cu system consisted of major (Cu, Ni) 6 Sn 5 and minor Cu 3 Sn IMCs, and the grain morphology of (Cu, Ni) 6 Sn 5 IMCs subsequently exhibited fine rounded, needlelike and coarse rounded shapes from the Ni side to the Cu side, which was highly in accordance with the Ni concentration gradient across the joints. However, in the ultrasound-induced TLP soldering process, the intermetallic joints formed in Ni/Sn/Cu system only consisted of the (Cu, Ni) 6 Sn 5 IMCs which exhibited an uniform grain morphology of rounded shape with a remarkably narrowed Ni concentration gradient. The ultrasound-induced homogeneous intermetallic joints exhibited higher shear strength (61.6 MPa) than the traditional heterogeneous intermetallic joints (49.8 MPa). Copyright © 2017 Elsevier B.V. All rights reserved.

A new active solder for joining electronic components

DOE Office of Scientific and Technical Information (OSTI.GOV)

SMITH,RONALD W.; VIANCO,PAUL T.; HERNANDEZ,CYNTHIA L.

Electronic components and micro-sensors utilize ceramic substrates, copper and aluminum interconnect and silicon. The joining of these combinations require pre-metallization such that solders with fluxes can wet such combinations of metals and ceramics. The paper will present a new solder alloy that can bond metals, ceramics and composites. The alloy directly wets and bonds in air without the use flux or premetallized layers. The paper will present typical processing steps and joint microstructures in copper, aluminum, aluminum oxide, aluminum nitride, and silicon joints.

Soldering Technology. Proceedings of Annual Seminar (8th) Held on 22-23 February 1984

DTIC Science & Technology

1984-02-01

conducted and test data proves that they can not only be cost effective, but that they also improve product quality. These proceedings are published for your...aoticr piobiem with tK old system. and density per assembly ranges from 10 to 650 Very little or no data was recorded to evaluate the components. In the...soldering. This process, illustrated in on each board. Figure 2. provides engineering with the data 9 Defined Solder Screen - The same defect on needed and

Suppressing tin whisker growth in lead-free solders and platings

DOEpatents

Hoffman, Elizabeth N; Lam, Poh-Sang

2014-04-29

A process of irradiation Sn containing Pb-free solder to mitigate whisker formation and growth thereon is provided. The use of gamma radiation such as cobalt-60 has been applied to a substrate of Sn on copper has been found to change the morphology of the crystalline whisker growth to a more truncated hillock pattern. The change in morphology greatly reduces the tendency of whiskers to contribute to electrical short-circuits being used as a Pb-free solder system on a copper substrate.

Methods of making metallic glass foil laminate composites

DOEpatents

Vianco, P.T.; Fisher, R.W.; Hosking, F.M.; Zanner, F.J.

1996-08-20

A process for the fabrication of a rapidly solidified foil laminate composite. An amorphous metallic glass foil is flux treated and coated with solder. Before solidification of the solder the foil is collected on a take-up spool which forms the composite into a solid annular configuration. The resulting composite exhibits high strength, resiliency and favorable magnetic and electrical properties associated with amorphous materials. The composite also exhibits bonding strength between the foil layers which significantly exceeds the bulk strength of the solder alone. 6 figs.

Methods of making metallic glass foil laminate composites

DOEpatents

Vianco, Paul T.; Fisher, Robert W.; Hosking, Floyd M.; Zanner, Frank J.

1996-01-01

A process for the fabrication of a rapidly solidified foil laminate composite. An amorphous metallic glass foil is flux treated and coated with solder. Before solidification of the solder the foil is collected on a take-up spool which forms the composite into a solid annular configuration. The resulting composite exhibits high strength, resiliency and favorable magnetic and electrical properties associated with amorphous materials. The composite also exhibits bonding strength between the foil layers which significantly exceeds the bulk strength of the solder alone.

Thermal model for optimization of vascular laser tissue soldering.

PubMed

Bogni, Serge; Stumpp, Oliver; Reinert, Michael; Frenz, Martin

2010-06-01

Laser tissue soldering (LTS) is a promising technique for tissue fusion based on a heat-denaturation process of proteins. Thermal damage of the fused tissue during the laser procedure has always been an important and challenging problem. Particularly in LTS of arterial blood vessels strong heating of the endothelium should be avoided to minimize the risk of thrombosis. A precise knowledge of the temperature distribution within the vessel wall during laser irradiation is inevitable. The authors developed a finite element model (FEM) to simulate the temperature distribution within blood vessels during LTS. Temperature measurements were used to verify and calibrate the model. Different parameters such as laser power, solder absorption coefficient, thickness of the solder layer, cooling of the vessel and continuous vs. pulsed energy deposition were tested to elucidate their impact on the temperature distribution within the soldering joint in order to reduce the amount of further animal experiments. A pulsed irradiation with high laser power and high absorbing solder yields the best results. (c) 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Microstructure and Mechanical Properties of Tin-Bismuth Solder Reinforced by Aluminum Borate Whiskers

NASA Astrophysics Data System (ADS)

Wang, Jun; Wei, Hongmei; He, Peng; Lin, Tiesong; Lu, Fengjiao

2015-10-01

Tin-bismuth solder has emerged as a promising lead-free alternative to tin-lead solder, especially for low-temperature packaging applications. However, the intrinsic brittleness of tin-bismuth solder alloy, aggravated by the coarse bismuth-rich phase and the thick interfacial intermetallic layer, notably limits the mechanical performance of the bonded joints. In this work, the microstructure and mechanical performance of solder joints were improved by adding 3.2 vol.% aluminum borate whiskers to the tin-bismuth solder alloy. This whisker-reinforced composite solder was fabricated through a simple process. Typically, 25- μm to 75- μm tin-bismuth particles were mixed with a small amount of aluminum borate whiskers with diameter of 0.5 μm to 1.5 μm and length of 5 μm to 15 μm. The addition of whiskers restrained the formation of coarse brittle bismuth-rich phase and decreased the lamellar spacing from 0.84 μm to 7.94 μm to the range of 0.22 μm to 1.80 μm. Moreover, the growth rate of the interfacial intermetallic layer during the remelting treatment decreased as well. The joint shear strength increased from 19.4 MPa to 24.7 MPa, and only declined by 4.9% (average, -5.9% to 15.8%) after the tenth remelting, while the shear strength of the joint without whiskers declined by 31.5% (average, 10.1-44.1%). The solder alloy was reinforced because of their high strength and high modulus and also the refinement effect on the solder alloy microstructure.

Dye-enhanced protein solders and patches in laser-assisted tissue welding.

PubMed

Small, W; Heredia, N J; Maitland, D J; Da Silva, L B; Matthews, D L

1997-01-01

This study examines the use of dye-enhanced protein bonding agents in 805 nm diode laser-assisted tissue welding. A comparison of an albumin liquid solder and collagen solid-matrix patches used to repair arteriotomies in an in vitro porcine model is presented. Extrinsic bonding media in the form of solders and patches have been used to enhance the practice of laser tissue welding. Preferential absorption of the laser wavelength has been achieved by the incorporation of chromophores. Both the solder and the patch included indocyanine green dye (ICG) to absorb the 805 nm continuous-wave diode laser light used to perform the welds. Solder-mediated welds were divided into two groups (high power/short exposure and low power/long exposure), and the patches were divided into three thickness groups ranging from 0.1 to 1.3 mm. The power used to activate the patches was constant, but the exposure time was increased with patch thickness. Burst pressure results indicated that solder-mediated and patched welds yielded similar average burst strengths in most cases, but the patches provided a higher success rate (i.e., more often exceeded 150 mmHg) and were more consistent (i.e., smaller standard deviation) than the solder. The strongest welds were obtained using 1.0-1.3 mm thick patches, while the high power/short exposure solder group was the weakest. Though the solder and patches yielded similar acute weld strengths, the solid-matrix patches facilitated the welding process and provided consistently strong welds. The material properties of the extrinsic agents influenced their performance.

Scanning electron microscopy observations of failures of implant overdenture bars: a case series report.

PubMed

Waddell, J Neil; Payne, Alan G T; Swain, Michael V; Kieser, Jules A

2010-03-01

Soldered or cast bars are used as a standard of care in attachment systems supporting maxillary and mandibular implant overdentures. When failures of these bars occur, currently there is a lack of evidence in relation to their specific etiology, location, or nature. To investigate the failure process of a case series of six failed soldered bars, four intact soldered bars, and one intact cast milled bar, which had been supporting implant overdentures. A total of 11 different overdenture bars were removed from patients with different configuration of opposing arches. A failed bar (FB) group (n = 6) had failed soldered overdenture bars, which were recovered from patients following up to 2 years of wear before requiring prosthodontic maintenance and repair. An intact bar (IB) group (n = 5) had both soldered bars and a single cast milled bar, which had been worn by patients for 2 to 5 years prior to receiving other aspects of prosthodontic maintenance. All bars were examined using scanning electron microscopy to establish the possible mode of failure (FB) or to identify evidence of potential failure in the future (IB). Evidence of a progressive failure mode of corrosion fatigue and creep were observed on all the FB and IB usually around the solder areas and nonoxidizing gold cylinder. Fatigue and creep were also observed in all the IB. Where the level of corrosion was substantial, there was no evidence of wear from the matrices of the attachment system. Evidence of an instantaneous failure mode, ductile and brittle overload, was observed on the fracture surfaces of all the FB, within the solder and the nonoxidizing gold cylinders, at the solder/cylinder interface. Corrosion, followed by corrosion fatigue, appears to be a key factor in the onset of the failure process for overdenture bars in this case series of both maxillary and mandibular overdentures. Limited sample size and lack of standardization identify trends only but prevent broad interpretation of the findings.

A Probabilistic Approach to Predict Thermal Fatigue Life for Ball Grid Array Solder Joints

NASA Astrophysics Data System (ADS)

Wei, Helin; Wang, Kuisheng

2011-11-01

Numerous studies of the reliability of solder joints have been performed. Most life prediction models are limited to a deterministic approach. However, manufacturing induces uncertainty in the geometry parameters of solder joints, and the environmental temperature varies widely due to end-user diversity, creating uncertainties in the reliability of solder joints. In this study, a methodology for accounting for variation in the lifetime prediction for lead-free solder joints of ball grid array packages (PBGA) is demonstrated. The key aspects of the solder joint parameters and the cyclic temperature range related to reliability are involved. Probabilistic solutions of the inelastic strain range and thermal fatigue life based on the Engelmaier model are developed to determine the probability of solder joint failure. The results indicate that the standard deviation increases significantly when more random variations are involved. Using the probabilistic method, the influence of each variable on the thermal fatigue life is quantified. This information can be used to optimize product design and process validation acceptance criteria. The probabilistic approach creates the opportunity to identify the root causes of failed samples from product fatigue tests and field returns. The method can be applied to better understand how variation affects parameters of interest in an electronic package design with area array interconnections.

[Atorvastatin improves reflow after percutaneous coronary intervention in patients with acute ST-segment elevation myocardial infarction by decreasing serum uric acid level].

PubMed

Yan, Ling; Ye, Lu; Wang, Kun; Zhou, Jie; Zhu, Chunjia

2016-05-25

Objective: To investigate the effect of atorvastatin on reflow in patients with acute ST-segment elevation myocardial infarction (STEMI) after percutaneous coronary intervention (PCI) and its relation to serum uric acid levels. Methods: One hundred and fourteen STEMI patients undergoing primary PCI were enrolled and randomly divided into two groups:55 cases received oral atorvastatin 20 mg before PCI (routine dose group) and 59 cases received oral atorvastatin 80 mg before PCI (high dose group). According to the initial serum uric acid level, patients in two groups were further divided into normal uric acid subgroup and hyperuricemia subgroup. The changes of uric acid level and coronary artery blood flow after PCI were observed. Correlations between the decrease of uric acid, the dose of atorvastatin and the blood flow of coronary artery after PCI were analyzed. Results: Serum uric acid levels were decreased after treatment in both groups (all P <0.05), and patients with hyperuricemia showed more significant decrease in serum uric acid level ( P <0.05). Compared with the routine dose group, serum uric acid level in patients with hyperuricemia decreased more significantly in the high dose group ( P <0.05), but no significant difference was observed between patients with normal serum uric acid levels in two groups ( P >0.05). Among 114 patients, there were 19 cases without reflow after PCI (16.7%). In the routine dose group, there were 12 patients without reflow, in which 3 had normal uric acid and 9 had high uric acid levels ( P <0.01). In the high dose group, there were 7 patients without reflow, in which 2 had normal uric acid and 5 had high uric acid ( P <0.05). Logistic regression analysis showed that hyperuricemia was one of independent risk factors for no-reflow after PCI ( OR =1.01, 95% CI :1.01-1.11, P <0.01). The incidence of no-flow after PCI in the routine dose group was 21.8% (12/55), and that in the high dose group was 11.9% (7/59) ( P <0.01). Conclusion: High dose atorvastatin can decrease serum uric acid levels and improve reflow after PCI in patients with STEMI.

Abnormal myocardial fluid retention as an early manifestation of ischemic injury.

PubMed Central

Willerson, J. T.; Scales, F.; Mukherjee, A.; Platt, M.; Templeton, G. H.; Fink, G. S.; Buja, L. M.

1977-01-01

Fifty-seven isolated, blood perfused, continuously weighed canine hearts have been utilized to study the development of abnormal myocardial fluid retention during early myocardial ischemic injury. Inflatable balloon catheters were positioned around the left anterior descending coronary arteries (LAD) of 54 hearts or the proximal left circumflex coronary arteries of three hearts for study of the following intervals of coronary occlusion: a) 10 minutes followed by 20 minutes of reflow, b) 40 minutes followed by either no reflow or by 20 minutes of reflow, and c) 60 minutes without reflow. After 60 minutes of fixed coronary occlusion, histologic and ultrastructural examination revealed mild swelling of many ischemic cardiac muscle cells in the absence of interstitial edema, cardiac weight gain, and obvious structural defects in cell membrane integrity. After 40 minutes of coronary occlusion and 20 minutes of reflow, significant cardiac weight gain occurred in association with characteristic alterations in the ischemic region, including widespread interstitial edema and focal vascular congestion and hemorrhage and swelling of cardiac muscle cells. Focal structural defects in cell membrane integrity were also noted. The development of abnormal myocardial fluid retention after 40 minutes of LAD occlusion occurred in association with a significant reduction in sodium-potassium-ATPase activity in the ischemic area, but with no significant alteration in either creatine phosphokinase or citrate synthase activity in the same region. Despite the abnormal myocardial fluid retention in these hearts, it was possible pharmacologically to vasodilate coronary vessels with adenosine and nitroglycerin infusion to maintain a consistently high coronary flow following release of the coronary occlusion after 40 minutes and to even exceed initial hyperemic flow values following release of the occlusion when adenosine and nitroglycerin infusion was delayed until 15 minutes after reflow. Thus, the data indicate that impaired cell volume regulation and interstitial fluid accumulation and focal structural defects in cell membrane integrity are early manifestations of ischemic injury followed by reflow, but fail to establish a major role for the abnormal fluid retention in altering coronary blood flow prior to the development of extensive myocardial necrosis. In contrast, fixed coronary occlusion for 60 minutes results in mild intracellular swelling but no significant interstitial edema and no obvious structural defects in cell membrane integrity. Images Figure 1 Figure 5 Figure 6 Figure 2 Figure 3 Figure 4 PMID:139829

Development of Stable, Low Resistance Solder Joints for a Space-Flight HTS Lead Assemblies

NASA Technical Reports Server (NTRS)

Canavan, Edgar R.; Chiao, Meng; Panashchenko, Lyudmyla; Sampson, Michael

2017-01-01

The solder joints in spaceflight high temperature superconductor (HTS) lead assemblies for certain astrophysics missions have strict constraints on size and power dissipation. In addition, the joints must tolerate years of storage at room temperature, many thermal cycles, and several vibration tests between their manufacture and their final operation on orbit. As reported previously, solder joints between REBCO coated conductors and normal metal traces for the Astro-H mission showed low temperature joint resistance that grew approximately as log time over the course of months. Although the assemblies worked without issue in orbit, for the upcoming X-ray Astrophysics Recovery Mission we are attempting to improve our solder process to give lower, more stable, and more consistent joint resistance. We produce numerous sample joints and measure time- and thermal cycle-dependent resistance, and characterize the joints using x-ray and other analysis tools. For a subset of the joints, we use SEMEDS to try to understand the physical and chemical processes that effect joint behavior.

Neutrophil/Lymphocyte Ratio as a Predictor of In-Hospital Major Adverse Cardiac Events, New-Onset Atrial Fibrillation, and No-Reflow Phenomenon in Patients with ST Elevation Myocardial Infarction.

PubMed

Wagdy, Sherif; Sobhy, Mohamed; Loutfi, Mohamed

2016-01-01

Neutrophil/lymphocyte (N/L) ratio represents the balance between neutrophil and lymphocyte counts in the body and can be utilized as an index for systemic inflammatory status. The no-reflow phenomenon is defined as inadequate myocardial perfusion through a given segment of the coronary circulation without angiographic evidence of mechanical vessel obstruction. Systemic inflammatory status has been associated with new-onset atrial fibrillation (NOAF) as well as no-reflow. To evaluate the predictive value of N/L ratio for in-hospital major adverse events, NOAF, and no-reflow in patients with ST elevation myocardial infarction (STEMI). Two hundred consecutive patients with STEMI presenting to Alexandria Main University Hospital and International Cardiac Center Hospital, Alexandria, Egypt, from April 2013 to October 2013 were included in this study. Laboratory investigation upon admission included complete blood count with mean platelet volume (MPV) and N/L ratio, and random plasma glucose (RPG) level. The results of coronary angiography indicating the infarct-related artery (IRA), initial thrombolysis in myocardial infarction (TIMI) flow in the IRA, and the TIMI flow after stenting were recorded. The patients were studied according to the presence of various clinical and laboratory variables, such as age, gender, pain-to-balloon time, location of the infarction, RPG level and complete blood count including N/L ratio and MPV on admission, and initial TIMI flow in the IRA. They were also evaluated for the final TIMI flow after the primary percutaneous coronary intervention, incidence of NOAF, and the incidence of in-hospital major adverse cardiac events (MACE). The incidence rate of no-reflow, NOAF, and in-hospital MACE was 13.2%, 8%, and 5%, respectively, with cardiac death as the predominant form of in-hospital MACE. The group of no-reflow, NOAF, and/or MACE showed significantly older age (62.29 ± 7.90 vs 56.30 ± 10.34, P = 0.014), longer pain-to-balloon time (15.90 ± 7.87 vs 6.08 ± 3.82 hours, P < 0.001), higher levels of RPG, N/L ratio (8.19 ± 3.05 vs 5.44 ± 3.53, P, 0.001), and MPV (11.90 ± 2.09 vs 8.58 ± 1.84 fL, P < 0.001) on admission. After adjustment of confounding factors, the independent predictors of NOAF, no-reflow, and in-hospital MACE were higher N/L ratio (odds ratio [OR] = 3.5, P = 0.02) and older age (OR = 3.1, P = 0.04). Older patient age, longer pain-to-balloon time, hyperglycemia, higher N/L ratio, and MPV on admission are useful predictive factors for the occurrence of no-reflow postprimary percutaneous coronary intervention, NOAF, and/or in-hospital MACE. N/L ratio is a new strong independent predictor of no-reflow, NOAF, and/or in-hospital MACE in patients with STEMI. The use of this simple routine biomarker may have a potential therapeutic implication in preventing NOAF and improving prognosis in STEMI revascularized patients.

Pb-free surface-finishing on electronic components' terminals for Pb-free soldering assembly

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tanaka, Hitoshi; Tanimoto, Morimasa; Matsuda, Akira

1999-11-01

Pb-free solderable surface finishing is essential to implement Pb-free solder assembly in order to meet with the growing demand of environmental consciousness to eliminate Pb from electronic products. Two types of widely applicable Pb-free surface finishing technologies are developed. One is the multilayer-system including Pd with Ni undercoat. Heat-resistance of Pd enables whole-surface-plating on to leadframe before IC-assembling process. The other is the double-layer-system with low-melting-point-materials, for example, thicker Sn underlayer and thinner Sn-Bi alloy overlayer, dilutes Sn-Bi alloy's defects of harmful reactivity along with substrate metal and mechanical brittleness with keeping its advantages of solder-wettability and no whisker.

Synthesis of the thermoelectric nanopowder recovered from the used thermoelectric modules.

PubMed

Lee, Kun-Jae; Jin, Yun-Ho; Kong, Man-Sik

2014-10-01

We fabricated the thermoelectric powder using the used thermoelectric modules in a vehicle. As a starting material, the used thermoelectric modules were collected and separated to substrate, electrode, solder, and thermoelectric parts by a thermal process. The separation process was performed in a wet process at the critical temperature. The solder in the module was the neighbor part of the thermoelectric material with the lowest melting temperature in the module. We focused on the thermal property of the solder to separate the thermoelectric chips in the module. After the separation process, we prepared the pure thermoelectric material by the chemical etching for an impurity removal. Also the thermoelectric nanopowder was fabricated by a chemical reduction reaction using the recycled thermoelectric materials. The recovered nanopowder was confirmed to the phase of bismuth telluride (Bi2Te3) with the particle size of -15 nm.

Real-time wetting dynamics and interfacial chemistry in low-melting 57Bi-42Sn-1Ag solder paste on Ni-Au

NASA Astrophysics Data System (ADS)

Bozack, M. J.

2004-11-01

We report the observation of real-time, in situ, wetting and spreading dynamics for 57Bi-42Sn-1Ag solder paste on Ni-Au surfaces during melting in a scanning electron microscope. The 57Bi-42Sn-1Ag is a low melting (139 °C) Pb-free eutectic alloy currently under consideration by automobile manufacturers for use in instrument displays. We find that, while there is excellent wetting of 57Bi-42Sn-1Ag solder paste on Ni-Au, there is almost no spreading. A large amount of Bi segregates to the surface of 57Bi-42Sn-1Ag solder balls during the sintering process. At melting, excessive flux outgassing and pooling are observed, several melted solder balls float on top of the flux, and substantial elemental segregation occurs during the first minutes of wetting. Neither Ni nor Au fully intermixes throughout the alloy at the interface within seconds of wetting. Bi does not move outward with the expanding alloy front. This combination of detrimental effects forms voids in the solder paste, contributes to low reliability of solder joints, and complicates the materials science at the solder-substrate interface as shown by Auger electron spectroscopy. Reliability work in progress (3000 cycles) shows that 57Bi-42Sn-1Ag on Ni-Au is less reliable than eutectic Sn-37Pb on Ni-Au for 2512 chip resistors cycled from -40 to 125 °C.

Closure of skin incisions in rabbits by laser soldering II: Tensile strength.

PubMed

Brosh, Tamar; Simhon, David; Halpern, Marisa; Ravid, Avi; Vasilyev, Tamar; Kariv, Naam; Nevo, Zvi; Katzir, Abraham

2004-01-01

The basic characteristic property of wound closure is the immediate and long-term tensile strength (LTS). The objective of the current study was to compare tissue laser soldering to other available methods (i.e., cyanoacrylate glues and sutures) in the performance and outcome of wound closure and reparative healing process, with an emphasis on the immediate and LTS. The animals were divided into three groups according to the type and details of the closure procedure. Group A: laser treatments at different temperatures were compared to sutured incisions, emphasizing the LTS after 10 days. Group B: laser soldering at 65 +/- 5 degrees C was compared to chemical glues (i.e., Histoacryl and Dermabond), emphasizing the immediate tensile strength (ITS). Group C: LTS of laser soldered incisions was compared to that of sutured incisions at various time intervals emphasizing LTS (3, 7, 14, 28 days). Group A: LTS at 60 degrees C exhibited the highest values (0.48 MPa). Group B: no ITS difference was detected between laser soldering and chemical glues. Group C: soldered incisions at 65 degrees C exhibited higher LTS (1.81 MPa) than that of sutured incisions (1.08 MPa) (P < 0.043). Temperature-controlled laser soldering at 65 degrees C provided sufficient ITS and higher bonding LTS values compared with sutures, resulting in better wound healing characteristics. The laser soldering system presented here should be tested on larger animal models before adopting it for clinical usage.

Orthodontic soldering techniques: aspects of quality assurance in the dental laboratory.

PubMed

Heidemann, Jutta; Witt, Emil; Feeg, Martin; Werz, Rainer; Pieger, Klaus

2002-07-01

In Germany, the dental technician is required by the Medical Products Act (MPG) to produce workpieces of high safety and quality and to document these properties. Soldering continues to be the prevailing joining technique in the dental laboratory, although problems arise from the susceptibility to corrosion and the low strength of soldered joints. This study aimed to reveal sources of defects in dental laboratory workpieces in order to achieve optimization in terms of quality assurance. The joints were produced by various dental technicians using three different soldering techniques. These joining techniques were investigated for their quality and their corrosion properties during immersion in ferric chloride, orthodontic appliance cleanser, and artificial saliva. Observance of the soldering instructions by the dental technicians was checked. Corrosion attack was confirmed by scanning electron microscopy and by measuring the ion concentrations of copper, silver and zinc in the corrosive agents, using atomic emission spectroscopy with stimulation by inductively coupled plasma (ICP-AES analysis). Incomplete filling of the soldering gap, porosities resulting from the production process, poor corrosion properties, and in particular a high variability of the measured values point to insufficient reliability of two soldering techniques. Variations in quality were also detected among the technicians' modes of operation. The analyses confirm the need for quality assurance of soldering techniques and for increased support for alternative joining techniques such as laser welding in the future. The results of the studies on laser welding are presented in a separate publication.

Time And Temperature Dependent Micromechanical Properties Of Solder Joints For 3D-Package Integration

NASA Astrophysics Data System (ADS)

Roellig, Mike; Meier, Karsten; Metasch, Rene

2010-11-01

The recent development of 3D-integrated electronic packages is characterized by the need to increase the diversity of functions and to miniaturize. Currently many 3D-integration concepts are being developed and all of them demand new materials, new designs and new processing technologies. The combination of simulation and experimental investigation becomes increasingly accepted since simulations help to shorten the R&D cycle time and reduce costs. Numerical calculations like the Finite-Element-Method are strong tools to calculate stress conditions in electronic packages resulting from thermal strains due to the manufacturing process and environmental loads. It is essential for the application of numerical calculations that the material data is accurate and describes sufficiently the physical behaviour. The developed machine allows the measurement of time and temperature dependent micromechanical properties of solder joints. Solder joints, which are used to mechanically and electrically connect different packages, are physically measured as they leave the process. This allows accounting for process influences, which may change material properties. Additionally, joint sizes and metallurgical interactions between solder and under bump metallization can be respected by this particular measurement. The measurement allows the determination of material properties within a temperature range of 20° C-200° C. Further, the time dependent creep deformation can be measured within a strain-rate range of 10-31/s-10-81/s. Solder alloys based on Sn-Ag/Sn-Ag-Cu with additionally impurities and joint sizes down to O/ 200 μm were investigated. To finish the material characterization process the material model coefficient were extracted by FEM-Simulation to increase the accuracy of data.

All-polymer photonic sensing platform based on whispering-gallery mode microgoblet lasers.

PubMed

Wienhold, T; Kraemmer, S; Wondimu, S F; Siegle, T; Bog, U; Weinzierl, U; Schmidt, S; Becker, H; Kalt, H; Mappes, T; Koeber, S; Koos, C

2015-09-21

We present an all-polymer photonic sensing platform based on whispering-gallery mode microgoblet lasers integrated into a microfluidic chip. The chip is entirely made from polymers, enabling the use of the devices as low-cost disposables. The microgoblet cavities feature quality factors exceeding 10(5) and are fabricated from poly(methyl methacrylate) (PMMA) using spin-coating, mask-based optical lithography, wet chemical etching, and thermal reflow. In contrast to silica-based microtoroid resonators, this approach replaces technically demanding vacuum-based dry etching and serial laser-based reflow techniques by solution-based processing and parallel thermal reflow. This enables scaling to large-area substrates, and hence significantly reduces device costs. Moreover, the resonators can be fabricated on arbitrary substrate materials, e.g., on transparent and flexible polymer foils. Doping the microgoblets with the organic dye pyrromethene 597 transforms the passive resonators into lasers. Devices have lasing thresholds below 0.6 nJ per pulse and can be efficiently pumped via free-space optics using a compact and low-cost green laser diode. We demonstrate that arrays of microgoblet lasers can be readily integrated into a state-of-the-art microfluidic chip replicated via injection moulding. In a proof-of-principle experiment, we show the viability of the lab-on-a-chip via refractometric sensing, demonstrating a bulk refractive index sensitivity (BRIS) of 10.56 nm per refractive index unit.

Evaluation of Electrochemical Migration on Printed Circuit Boards with Lead-Free and Tin-Lead Solder

NASA Astrophysics Data System (ADS)

He, Xiaofei; Azarian, Michael H.; Pecht, Michael G.

2011-09-01

To evaluate the current leakage and electrochemical migration behavior on printed circuit boards with eutectic tin-lead and lead-free solder, IPC B-24 comb structures were exposed to 65°C and 88% relative humidity conditions under direct-current (DC) bias for over 1500 h. These boards were processed with either Sn-3.0Ag-0.5Cu solder or Sn-37Pb solder. In addition to solder alloy, board finish (organic solderability preservative versus lead-free hot air solder leveling), spacing (25 mil versus 12.5 mil), and voltage (40 V versus 5 V bias) were also assessed by using in situ measurements of surface insulation resistance (SIR) and energy-dispersive spectroscopy after testing. It was shown that an initial increase of SIR was caused by consumption of electroactive species on the surface, intermittent drops of SIR were caused by dendritic growth, and a long-term SIR decline was caused by electrodeposition of a metallic layer. The prolonged SIR decline of Sn-3.0Ag-0.5Cu boards was simulated by three-dimensional (3D) progressive and instantaneous nucleation models, whose predictions were compared with experimental data. Sn-37Pb boards exhibited comigration of Sn, Pb, and Cu, while Sn-3.0Ag-0.5Cu boards incurred comigration of Sn, Ag, and Cu. Among the migrated species, Sn always dominated and was observed as either a layer or in polyhedral deposits, Pb was the most common element found in the dendrites, Cu was a minor constituent, and Ag migrated only occasionally. Compared with solder alloy, board finishes played a secondary role in affecting SIR due to their complexation with or dissolution into the solder. The competing effect between electric field and spacing was also investigated.

Soldering of Mg Joints Using Zn-Al Solders

NASA Astrophysics Data System (ADS)

Gancarz, Tomasz; Berent, Katarzyna; Skuza, Wojciech; Janik, Katarzyna

2018-07-01

Magnesium has applications in the automotive and aerospace industries that can significantly contribute to greater fuel economy and environmental conservation. The Mg alloys used in the automotive industry could reduce mass by up to 70 pct, providing energy savings. However, alongside the advantages there are limitations and technological barriers to use Mg alloys. One of the advantages concerns phenomena occurring at the interface when joining materials investigated in this study, in regard to the effect of temperature and soldering time for pure Mg joints. Eutectic Zn-Al and Zn-Al alloys with 0.05 (wt pct) Li and 0.2 (wt pct) Na were used in the soldering process. The process was performed for 3, 5, and 8 minutes of contact, at temperatures of 425 °C, 450 °C, 475 °C, and 500 °C. Selected, solidified solder-substrate couples were cross-sectioned, and their interfacial microstructures were investigated by scanning electron microscopy. The experiment was designed to demonstrate the effect of time, temperature, and the addition of Li and Na on the kinetics of the dissolving Mg substrate. The addition of Li and Na to eutectic Zn-Al caused to improve mechanical properties. Higher temperatures led to reduced joint strength, which is caused by increased interfacial reaction.

Electrochemical Behavior of Sn-9Zn-xTi Lead-Free Solders in Neutral 0.5M NaCl Solution

NASA Astrophysics Data System (ADS)

Wang, Zhenghong; Chen, Chuantong; Jiu, Jinting; Nagao, Shijo; Nogi, Masaya; Koga, Hirotaka; Zhang, Hao; Zhang, Gong; Suganuma, Katsuaki

2018-03-01

Electrochemical techniques were employed to study the electrochemical corrosion behavior of Sn-9Zn-xTi (x = 0, 0.05, 0.1, 0.2 wt.%) lead-free solders in neutral 0.5M NaCl solution, aiming to figure out the effect of Ti content on the corrosion properties of Sn-9Zn, providing information for the composition design of Sn-Zn-based lead-free solders from the perspective of corrosion. EIS results reveal that Ti addition was involved in the corrosion product layer and changed electrochemical interface behavior from charge transfer control process to diffusion control process. The trace amount of Ti addition (0.05 wt.%) can refine the microstructure and improve the corrosion resistance of Sn-9Zn solder, evidenced by much lower corrosion current density (i corr) and much higher total resistance (R t). Excess Ti addition (over 0.1 wt.%) led to the formation of Ti-containing IMCs, which were confirmed as Sn3Ti2 and Sn5Ti6, deteriorating the corrosion resistance of Sn-9Zn-xTi solders. The main corrosion products were confirmed as Sn3O(OH)2Cl2 mixed with small amount of chlorine/oxide Sn compounds.

Soldering of Mg Joints Using Zn-Al Solders

NASA Astrophysics Data System (ADS)

Gancarz, Tomasz; Berent, Katarzyna; Skuza, Wojciech; Janik, Katarzyna

2018-04-01

Magnesium has applications in the automotive and aerospace industries that can significantly contribute to greater fuel economy and environmental conservation. The Mg alloys used in the automotive industry could reduce mass by up to 70 pct, providing energy savings. However, alongside the advantages there are limitations and technological barriers to use Mg alloys. One of the advantages concerns phenomena occurring at the interface when joining materials investigated in this study, in regard to the effect of temperature and soldering time for pure Mg joints. Eutectic Zn-Al and Zn-Al alloys with 0.05 (wt pct) Li and 0.2 (wt pct) Na were used in the soldering process. The process was performed for 3, 5, and 8 minutes of contact, at temperatures of 425 °C, 450 °C, 475 °C, and 500 °C. Selected, solidified solder-substrate couples were cross-sectioned, and their interfacial microstructures were investigated by scanning electron microscopy. The experiment was designed to demonstrate the effect of time, temperature, and the addition of Li and Na on the kinetics of the dissolving Mg substrate. The addition of Li and Na to eutectic Zn-Al caused to improve mechanical properties. Higher temperatures led to reduced joint strength, which is caused by increased interfacial reaction.

Electrochemical Behavior of Sn-9Zn- xTi Lead-Free Solders in Neutral 0.5M NaCl Solution

NASA Astrophysics Data System (ADS)

Wang, Zhenghong; Chen, Chuantong; Jiu, Jinting; Nagao, Shijo; Nogi, Masaya; Koga, Hirotaka; Zhang, Hao; Zhang, Gong; Suganuma, Katsuaki

2018-05-01

Electrochemical techniques were employed to study the electrochemical corrosion behavior of Sn-9Zn- xTi ( x = 0, 0.05, 0.1, 0.2 wt.%) lead-free solders in neutral 0.5M NaCl solution, aiming to figure out the effect of Ti content on the corrosion properties of Sn-9Zn, providing information for the composition design of Sn-Zn-based lead-free solders from the perspective of corrosion. EIS results reveal that Ti addition was involved in the corrosion product layer and changed electrochemical interface behavior from charge transfer control process to diffusion control process. The trace amount of Ti addition (0.05 wt.%) can refine the microstructure and improve the corrosion resistance of Sn-9Zn solder, evidenced by much lower corrosion current density ( i corr) and much higher total resistance ( R t). Excess Ti addition (over 0.1 wt.%) led to the formation of Ti-containing IMCs, which were confirmed as Sn3Ti2 and Sn5Ti6, deteriorating the corrosion resistance of Sn-9Zn- xTi solders. The main corrosion products were confirmed as Sn3O(OH)2Cl2 mixed with small amount of chlorine/oxide Sn compounds.

Recycling of lead solder dross, Generated from PCB manufacturing

NASA Astrophysics Data System (ADS)

Lucheva, Biserka; Tsonev, Tsonio; Iliev, Peter

2011-08-01

The main purpose of this work is to analyze lead solder dross, a waste product from manufacturing of printed circuit boards by wave soldering, and to develop an effective and environmentally sound technology for its recycling. A methodology for determination of the content and chemical composition of the metal and oxide phases of the dross is developed. Two methods for recycling of lead solder dross were examined—carbothermal reduction and recycling using boron-containing substances. The influence of various factors on the metal yield was studied and the optimal parameters of the recycling process are defined. The comparison between them under the same parameters-temperature and retention time, showed that recycling of dross with a mixture of borax and boric acid in a 1:2 ratio provides higher metal yield (93%). The recycling of this hazardous waste under developed technology gets glassy slag and solder, which after correction of the chemical composition can be used again for production of PCB.

Photothermal effects of laser tissue soldering.

PubMed

McNally, K M; Sorg, B S; Welch, A J; Dawes, J M; Owen, E R

1999-04-01

Low-strength anastomoses and thermal damage of tissue are major concerns in laser tissue welding techniques where laser energy is used to induce thermal changes in the molecular structure of the tissues being joined, hence allowing them to bond together. Laser tissue soldering, on the other hand, is a bonding technique in which a protein solder is applied to the tissue surfaces to be joined, and laser energy is used to bond the solder to the tissue surfaces. The addition of protein solders to augment tissue repair procedures significantly reduces the problems of low strength and thermal damage associated with laser tissue welding techniques. Investigations were conducted to determine optimal solder and laser parameters for tissue repair in terms of tensile strength, temperature rise and damage and the microscopic nature of the bonds formed. An in vitro study was performed using an 808 nm diode laser in conjunction with indocyanine green (ICG)-doped albumin protein solders to repair bovine aorta specimens. Liquid and solid protein solders prepared from 25% and 60% bovine serum albumin (BSA), respectively, were compared. The efficacy of temperature feedback control in enhancing the soldering process was also investigated. Increasing the BSA concentration from 25% to 60% greatly increased the tensile strength of the repairs. A reduction in dye concentration from 2.5 mg ml(-1) to 0.25 mg ml(-1) was also found to result in an increase in tensile strength. Increasing the laser irradiance and thus surface temperature resulted in an increased severity of histological injury. Thermal denaturation of tissue collagen and necrosis of the intimal layer smooth muscle cells increased laterally and in depth with higher temperatures. The strongest repairs were produced with an irradiance of 6.4 W cm(-2) using a solid protein solder composed of 60% BSA and 0.25 mg ml(-1) ICG. Using this combination of laser and solder parameters, surface temperatures were observed to reach 85+/-5 degrees C with a maximum temperature difference through the 150 microm thick solder strips of about 15 degrees C. Histological examination of the repairs formed using these parameters showed negligible evidence of collateral thermal damage to the underlying tissue. Scanning electron microscopy suggested albumin intertwining within the tissue collagen matrix and subsequent fusion with the collagen as the mechanism for laser tissue soldering. The laser tissue soldering technique is shown to be an effective method for producing repairs with improved tensile strength and minimal collateral thermal damage over conventional laser tissue welding techniques.

Eutectic-based wafer-level-packaging technique for piezoresistive MEMS accelerometers and bond characterization using molecular dynamics simulations

NASA Astrophysics Data System (ADS)

Aono, T.; Kazama, A.; Okada, R.; Iwasaki, T.; Isono, Y.

2018-03-01

We developed a eutectic-based wafer-level-packaging (WLP) technique for piezoresistive micro-electromechanical systems (MEMS) accelerometers on the basis of molecular dynamics analyses and shear tests of WLP accelerometers. The bonding conditions were experimentally and analytically determined to realize a high shear strength without solder material atoms diffusing to adhesion layers. Molecular dynamics (MD) simulations and energy dispersive x-ray (EDX) spectrometry done after the shear tests clarified the eutectic reaction of the solder materials used in this research. Energy relaxation calculations in MD showed that the diffusion of solder material atoms into the adhesive layer was promoted at a higher temperature. Tensile creep MD simulations also suggested that the local potential energy in a solder material model determined the fracture points of the model. These numerical results were supported by the shear tests and EDX analyses for WLP accelerometers. Consequently, a bonding load of 9.8 kN and temperature of 300 °C were found to be rational conditions because the shear strength was sufficient to endure the polishing process after the WLP process and there was little diffusion of solder material atoms to the adhesion layer. Also, eutectic-bonding-based WLP was effective for controlling the attenuation of the accelerometers by determining the thickness of electroplated solder materials that played the role of a cavity between the accelerometers and lids. If the gap distance between the two was less than 6.2 µm, the signal gains for x- and z-axis acceleration were less than 20 dB even at the resonance frequency due to air-damping.

Use of optical technique for inspection of warpage of IC packages

NASA Astrophysics Data System (ADS)

Toh, Siew-Lok; Chau, Fook S.; Ong, Sim Heng

2001-06-01

The packaging of IC packages has changed over the years, form dual-in-line, wire-bond, and pin-through-hole in printed wiring board technologies in the 1970s to ball grid array, chip scale and surface mount technologies in the 1990s. Reliability has been a big problem for manufacturers for some moisture-sensitive packages. One of the potential problems in plastic IC packages is moisture-induced popcorn effect which can arise during the reflow process. Shearography is a non-destructive inspection technique that may be used to detect the delamination and warpage of IC packages. It is non-contacting and permits a full-field observation of surface displacement derivatives. Another advantage of this technique is that it is able to give the real-time formation of the fringes which indicate flaws in the IC package under real-time simulation condition of Surface Mount Technology (SMT) IR reflow profile. It is extremely fast and convenient to study the true behavior of the packaging deformation during the SMT process. It can be concluded that shearography has the potential for the real- time detection, in situ and non-destructive inspection of IC packages during the surface mount process.

Dry Sintering Meets Wet Silver-Ion "Soldering": Charge-Transfer Plasmon Engineering of Solution-Assembled Gold Nanodimers From Visible to Near-Infrared I and II Regions.

PubMed

Fang, Lingling; Wang, Yueliang; Liu, Miao; Gong, Ming; Xu, An; Deng, Zhaoxiang

2016-11-07

Achieving highly tunable and localized surface plasmon resonance up to near infrared (NIR) regions is a key target in nanoplasmonics. In particular, a self-assembly process capable of producing highly uniform and solution-processable nanomaterials with tailor-made plasmonic properties is lacking. We herein address this problem through a conjunctive use of wet Ag + soldering and dry thermal sintering to produce nanodimer-derived structures with precisely engineered charge-transfer plasmon (CTP). The sintered dimers are water soluble, featuring gradually shifted CTP spanning an 800 nm wavelength range (up to NIR II). Upon silica removal, the products are grafted by DNA to offer surface functionality. This process is also adaptable to DNA-linked AuNP dimers toward plasmonic meta-materials via DNA-guided soldering and sintering. © 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Identification and chemical characterization of particulate matter from wave soldering processes at a printed circuit board manufacturing company.

PubMed

Szoboszlai, Z; Kertész, Zs; Szikszai, Z; Angyal, A; Furu, E; Török, Zs; Daróczi, L; Kiss, A Z

2012-02-15

In this case study, the elemental composition and mass size distribution of indoor aerosol particles were determined in a working environment where soldering of printed circuit boards (PCB) took place. Single particle analysis using ion and electron microscopy was carried out to obtain more detailed and reliable data about the origin of these particles. As a result, outdoor and indoor aerosol sources such as wave soldering, fluxing processes, workers' activity, mineral dust, biomass burning, fertilizing and other anthropogenic sources could be separated. With the help of scanning electron microscopy, characteristic particle types were identified. On the basis of the mass size distribution data, a stochastic lung deposition model was used to calculate the total and regional deposition efficiencies of the different types of particles within the human respiratory system. The information presented in this study aims to give insights into the detailed characteristics and the health impact of aerosol particles in a working environment where different kinds of soldering activity take place. Copyright © 2011 Elsevier B.V. All rights reserved.

Nanoscale characterization of 1D Sn-3.5Ag nanosolders and their application into nanowelding at the nanoscale

NASA Astrophysics Data System (ADS)

Zhang, Hong; Zhang, Junwei; Lan, Qianqian; Ma, Hongbin; Qu, Ke; Inkson, Beverley J.; Mellors, Nigel J.; Xue, Desheng; Peng, Yong

2014-10-01

One-dimensional Sn-3.5Ag alloy nanosolders have been successfully fabricated by a dc electrodeposition technique into nanoporous templates, and their soldering quality has been demonstrated in nanoscale electrical welding for the first time, which indicates that they can easily form remarkably reliable conductive joints. The electrical measurement shows that individual 1D Sn-3.5Ag nanosolders have a resistivity of 28.9 μΩ·cm. The morphology, crystal structure and chemistry of these nanosolders have been characterized at the nanoscale. It is found that individual 1D Sn-3.5Ag alloy nanosolders have a continuous morphology and smooth surface. XPS confirms the presence of tin and silver with a mass ratio of 96.54:3.46, and EDX elemental mappings clearly reveal that the Sn and Ag elements have a uniform distribution. Coveragent beam electron diffractions verify that the crystal phases of individual 1D Sn-3.5Ag alloy nanosolders consist of matrix β-Sn and the intermetallic compound Ag3Sn. The reflow experiments reveal that the eutectic composition of the 1D Sn-Ag alloy nanowire is shifted to the Sn rich corner. This work may contribute one of the most important tin-based alloy nanosolders for future nanoscale welding techniques, which are believed to have broad applications in nanotechnology and the future nano-industry.

Novel First-Level Interconnect Techniques for Flip Chip on MEMS Devices

PubMed Central

Sutanto, Jemmy; Anand, Sindhu; Patel, Chetan; Muthuswamy, Jit

2013-01-01

Flip-chip packaging is desirable for microelectro-mechanical systems (MEMS) devices because it reduces the overall package size and allows scaling up the number of MEMS chips through 3-D stacks. In this report, we demonstrate three novel techniques to create first-level interconnect (FLI) on MEMS: 1) Dip and attach technology for Ag epoxy; 2) Dispense technology for solder paste; 3) Dispense, pull, and attach technology (DPAT) for solder paste. The above techniques required no additional microfabrication steps, produced no visible surface contamination on the MEMS active structures, and generated high-aspect-ratio interconnects. The developed FLIs were successfully tested on MEMS moveable microelectrodes microfabricated by SUMMiTVTM process producing no apparent detrimental effect due to outgassing. The bumping processes were successfully applied on Al-deposited bond pads of 100 μm × 100 μm with an average bump height of 101.3 μm for Ag and 184.8 μm for solder (63Sn, 37Pb). DPAT for solder paste produced bumps with the aspect ratio of 1.8 or more. The average shear strengths of Ag and solder bumps were 78 MPa and 689 kPa, respectively. The electrical test on Ag bumps at 794 A/cm2 demonstrated reliable electrical interconnects with negligible resistance. These scalable FLI technologies are potentially useful for MEMS flip-chip packaging and 3-D stacking. PMID:24504168

Analysis of Al diffusion processes in TiN barrier layers for the application in silicon solar cell metallization

NASA Astrophysics Data System (ADS)

Kumm, J.; Samadi, H.; Chacko, R. V.; Hartmann, P.; Wolf, A.

2016-07-01

An evaporated Al layer is known as an excellent rear metallization for highly efficient solar cells, but suffers from incompatibility with a common solder process. To enable solar cell-interconnection and module integration, in this work the Al layer is complemented with a solder stack of TiN/Ti/Ag or TiN/NiV/Ag, in which the TiN layer acts as an Al diffusion barrier. X-ray photoelectron spectroscopy measurements prove that diffusion of Al through the stack and the formation of an Al2O3 layer on the stack's surface are responsible for a loss of solderability after a strong post-metallization anneal, which is often mandatory to improve contact resistance and passivation quality. An optimization of the reactive TiN sputter process results in a densification of the TiN layer, which improves its barrier quality against Al diffusion. However, measurements with X-ray diffraction and scanning electron microscopy show that small grains with vertical grain boundaries persist, which still offer fast diffusion paths. Therefore, the concept of stuffing is introduced. By incorporating oxygen into the grain boundaries of the sputtered TiN layer, Al diffusion is strongly reduced as confirmed by secondary ion mass spectroscopy profiles. A quantitative analysis reveals a one order of magnitude lower Al diffusion coefficient for stuffed TiN layers. This metallization system maintains its solderability even after strong post-metallization annealing at 425 °C for 15 min. This paper thus presents an industrially feasible, conventionally solderable, and long-term stable metallization scheme for highly efficient silicon solar cells.

Correlation between balloon release pressure and no-reflow in patients with acute myocardial infarction undergoing direct percutaneous coronary intervention.

PubMed

Wang, Yanfei; Yao, Min; Liu, Haibo; Yang, Yuejin; Xie, Junmin; Jia, Xinwei; Pan, Huanjun; Wang, Chunyan

2014-01-01

Balloon release pressure may increase the incidence of no reflow after direct percutaneous coronary intervention (PCI). This randomized controlled study was designed to analyze the correlation between balloon release pressure and no-reflow in patients with acute myocardial infarction (AMI) undergoing direct PCI. There were 156 AMI patients who underwent PCI from January 1, 2010 to December 31, 2012, and were divided into two groups according to the stent inflation pressure: a conventional pressure group and a high pressure group. After PCI, angiography was conducted to assess the thrombolysis in myocardial infarction (TIMI) grade with related artery. Examinations were undertaken on all patients before and after the operation including cardiac enzymes, total cholesterol, low-density lipoprotein, blood glucose, homocysteine , β-thromboglobulin (β-TG), Hamilton depression scale (HAMD) and self-rating anxiety scale (SAS). After interventional therapy, the afore-mentioned parameters in both the conventional pressure group and high pressure group were again analyzed. The results showed that CK-MB, HAMD, SAS were significantly different (P < 0.05) in all patients after PCI, especially the CK-MB in the high pressure group ((25.7 ± 7.6) U/L vs. (76.7 ± 11.8) U/L). CK-MB, HAMD, SAS, and β-TG were comparative before PCI but they were significantly changed (P < 0.05) after intervention. No-reflow phenomenon occurred in 13 patients in the high pressure group, which was significantly higher than in the conventional pressure group (17.11% vs. 6.25%, P < 0.05). In stent implantation, using a pressure less than 1823.4 kPa balloon to release pressure may be the better choice to reduce the occurrence of no-reflow following direct PCI.

The Effect of Gap Angle on Tensile Strength of Preceramic Base Metal Solder Joints.

PubMed

Fattahi, Farnaz; Hashemi Ardakani, Zahra; Hashemi Ardakani, Maryam

2015-12-01

Soldering is a process commonly used in fabricating dental prosthesis. Since most soldered prosthesis fail at the solder joints; the joint strength is of utmost importance. The purpose of this study was to evaluate the effect of gap angle on the tensile strength of base metal solder joints. A total number of 40 Ni-Cr samples were fabricated according to ADA/ISO 9693 specifications for tensile test. Samples were cut at the midpoint of the bar, and were placed at the considered angles by employing an explicitly designed device. They were divided into 4 groups regarding the gap angle; Group C (control group) with parallel gap on steady distance of 0.2mm, Group 1: 10°, Group 2: 20°, and Group3: 30° gap angles. When soldered, the specimens were all tested for tensile strength using a universal testing machine at a cross-head speed of 0.5 mm/min with a preload of 10N. Kruskal-Wallis H test was used to compare tensile strength among the groups (p< 0.05). The mean tensile strength values obtained from the study groups were respectively 307.84, 391.50, 365.18, and 368.86 MPa. The tensile strength was not statistically different among the four groups in general (p≤ 0.490). Making the gap angular at the solder joints and the subsequent unsteady increase of the gap distance would not change the tensile strength of the joint.

Process for reducing series resistance of solar-cell metal-contact systems with a soldering-flux etchant

DOEpatents

Coyle, R.T.; Barrett, J.M.

1982-05-04

Disclosed is a process for substantially reducing the series resistance of a solar cell having a thick film metal contact assembly thereon while simultaneously removing oxide coatings from the surface of the assembly prior to applying solder therewith. The process includes applying a flux to the contact assembly and heating the cell for a period of time sufficient to substantially remove the series resistance associated with the assembly by etching the assembly with the flux while simultaneously removing metal oxides from said surface of said assembly.

Process for reducing series resistance of solar cell metal contact systems with a soldering flux etchant

DOEpatents

Coyle, R. T.; Barrett, Joy M.

1984-01-01

Disclosed is a process for substantially reducing the series resistance of a solar cell having a thick film metal contact assembly thereon while simultaneously removing oxide coatings from the surface of the assembly prior to applying solder therewith. The process includes applying a flux to the contact assembly and heating the cell for a period of time sufficient to substantially remove the series resistance associated with the assembly by etching the assembly with the flux while simultaneously removing metal oxides from said surface of said assembly.

Circularly Polarized Microwave Antenna Element with Very Low Off-Axis Cross-Polarization

NASA Technical Reports Server (NTRS)

Greem. David; DuToit, Cornelis

2013-01-01

The goal of this work was to improve off-axis cross-polarization performance and ease of assembly of a circularly polarized microwave antenna element. To ease assembly, the initial design requirement of Hexweb support for the internal circuit part, as well as the radiating disks, was eliminated. There is a need for different plating techniques to improve soldering. It was also desirable to change the design to eliminate soldering as well as the need to use the Hexweb support. Thus, a technique was developed to build the feed without using solder, solving the lathing and soldering issue. Internal parts were strengthened by adding curvature to eliminate Hexweb support, and in the process, the new geometries of the internal parts opened the way for improving the off-axis cross-polarization performance as well. The radiating disks curvatures were increased for increased strength, but it was found that this also improved crosspolarization. Optimization of the curvatures leads to very low off-axis cross-polarization. The feed circuit was curved into a cylinder for improved strength, eliminating Hexweb support. An aperture coupling feed mechanism eliminated the need for feed pins to the disks, which would have required soldering. The aperture coupling technique also improves cross-polarization performance by effectively exciting the radiating disks very close to the antenna s central axis of symmetry. Because of the shape of the parts, it allowed for an all-aluminum design bolted together and assembled with no solder needed. The advantage of a solderless design is that the reliability is higher, with no single-point failure (solder), and no need for special plating techniques in order to solder the unit together. The shapes (curved or round) make for a more robust build without extra support materials, as well as improved offaxis cross-polarization.

Fatigue damage behavior of a surface-mount electronic package under different cyclic applied loads

NASA Astrophysics Data System (ADS)

Ren, Huai-Hui; Wang, Xi-Shu

2014-04-01

This paper studies and compares the effects of pull-pull and 3-point bending cyclic loadings on the mechanical fatigue damage behaviors of a solder joint in a surface-mount electronic package. The comparisons are based on experimental investigations using scanning electron microscopy (SEM) in-situ technology and nonlinear finite element modeling, respectively. The compared results indicate that there are different threshold levels of plastic strain for the initial damage of solder joints under two cyclic applied loads; meanwhile, fatigue crack initiation occurs at different locations, and the accumulation of equivalent plastic strain determines the trend and direction of fatigue crack propagation. In addition, simulation results of the fatigue damage process of solder joints considering a constitutive model of damage initiation criteria for ductile materials and damage evolution based on accumulating inelastic hysteresis energy are identical to the experimental results. The actual fatigue life of the solder joint is almost the same and demonstrates that the FE modeling used in this study can provide an accurate prediction of solder joint fatigue failure.

Comparison of laser-activated tissue solders and thrombin-activated cryoprecipitate for wound closure

NASA Astrophysics Data System (ADS)

Kayton, Mark L.; Libutti, Steven K.; Bessler, Marc; Allendorf, John D. F.; Eiref, Simon D.; Marx, Gerard; Mou, Xiaode; Morales, Alfredo M.; Treat, Michael R.; Nowygrod, Roman

1994-09-01

To determine the relative strengths of various biologic adhesives at several timepoints, we compared thrombin-activated SD (solvent-detergent treated) cryoprecipitate with laser- activated SD cryoprecipitate and a laser-activated, albumin-based glue. Male Sprague-Dawley rats (n equals 79) received four, 3-cm, dorsal skin incisions which were closed with either laser- activated cryoprecipitate, laser-activated albumin solder, thrombin-activated cryoprecipitate, or standard skin staples. The cryoprecipitate was derived from pooled human plasma and was treated with a solvent-detergent process, rendering it free of envelope-coated viruses (i.e., HBV, HIV). An 808-nm diode laser was used to activate each solder with an average duration of exposure of 75 seconds per incision. Animals were sacrificed for evaluation of wound tensile strength and histology at 0 hours, 2 hours, 4 hours, and 4 days. At all timepoints tested, laser-activated solders were significantly stronger than thrombin-activated cryoprecipitate (p < 0.03) and control wounds (p < 0.003). There was no significant difference in tensile strength between the two types of laser-activated solder at any timepoint.

Optimal parameters for laser tissue soldering: II. Premixed versus separate dye-solder techniques.

PubMed

McNally, K M; Sorg, B S; Chan, E K; Welch, A J; Dawes, J M; Owen, E R

2000-01-01

Laser tissue soldering by using an indocyanine green (ICG)-doped protein solder applied topically to the tissue surface and denatured with a diode laser was investigated in Part I of this study. The depth of light absorption was predominantly determined by the concentration of the ICG dye added to the solder. This study builds on that work with an in vitro investigation of the effects of limiting the zone of heat generation to the solder-tissue interface to determine whether more stable solder-tissue fusion can be achieved. An alternative laser tissue soldering technique was investigated, which increased light absorption at the vital solder-tissue interface. A thin layer of ICG dye was smeared over the surface to be treated, the protein solder was then placed directly on top of the dye, and the solder was denatured with an 808-nm diode laser. Because laser light at approximately 800 nm is absorbed primarily by the ICG dye, this thin layer of ICG solution restricted the heat source to the space between the solder and the tissue surfaces. A tensile strength analysis was conducted to compare the separate dye-solder technique with conventional techniques of laser tissue soldering for which a premixed dye-solder is applied directly to the tissue surface. The effect of hydration on bond stability of repairs formed by using both techniques was also investigated using tensile strength and scanning electron microscopy analysis. Equivalent results in terms of tensile strength were obtained for the premixed dye-solder technique using protein solders containing 0.25 mg/ml ICG (liquid solder, 220 +/- 35 N/cm(2); solid solder, 602 +/- 32 N/cm(2)) and for the separate dye-solder technique (liquid solder, 228 +/- 41 N/cm(2); solid solder, 578 +/- 29 N/cm(2)). The tensile strength of native bovine thoracic aorta was 596 +/- 31 N/cm(2). Repairs created by using the separate dye-solder technique were more stable during hydration than their premixed dye-solder counterparts. The conventional premixed dye-solder was simpler and approximately twice as fast to apply. The separate dye-solder technique, however, increased the shelf-life of the solder, because the dye was mixed at the time of the experiment, thus conserving its spectral absorbency properties. Two laser-assisted tissue soldering techniques have been evaluated for repairing aorta incisions in vitro. The advantages and disadvantages of each of these techniques are discussed. Copyright 2000 Wiley-Liss, Inc.

A novel dismantling process of waste printed circuit boards using water-soluble ionic liquid.

PubMed

Zeng, Xianlai; Li, Jinhui; Xie, Henghua; Liu, Lili

2013-10-01

Recycling processes for waste printed circuit boards (WPCBs) have been well established in terms of scientific research and field pilots. However, current dismantling procedures for WPCBs have restricted the recycling process, due to their low efficiency and negative impacts on environmental and human health. This work aimed to seek an environmental-friendly dismantling process through heating with water-soluble ionic liquid to separate electronic components and tin solder from two main types of WPCBs-cathode ray tubes and computer mainframes. The work systematically investigates the influence factors, heating mechanism, and optimal parameters for opening solder connections on WPCBs during the dismantling process, and addresses its environmental performance and economic assessment. The results obtained demonstrate that the optimal temperature, retention time, and turbulence resulting from impeller rotation during the dismantling process, were 250 °C, 12 min, and 45 rpm, respectively. Nearly 90% of the electronic components were separated from the WPCBs under the optimal experimental conditions. This novel process offers the possibility of large industrial-scale operations for separating electronic components and recovering tin solder, and for a more efficient and environmentally sound process for WPCBs recycling. Copyright © 2013 Elsevier Ltd. All rights reserved.

Dynamic spatio-temporal imaging of early reflow in a neonatal rat stroke model.

PubMed

Leger, Pierre-Louis; Bonnin, Philippe; Lacombe, Pierre; Couture-Lepetit, Elisabeth; Fau, Sebastien; Renolleau, Sylvain; Gharib, Abdallah; Baud, Olivier; Charriaut-Marlangue, Christiane

2013-01-01

The aim of the study was to better understand blood-flow changes in large arteries and microvessels during the first 15 minutes of reflow in a P7 rat model of arterial occlusion. Blood-flow changes were monitored by using ultrasound imaging with sequential Doppler recordings in internal carotid arteries (ICAs) and basilar trunk. Relative cerebral blood flow (rCBF) changes were obtained by using laser speckle Doppler monitoring. Tissue perfusion was measured with [(14)C]-iodoantipyrine autoradiography. Cerebral energy metabolism was evaluated by mitochondrial oxygen consumption. Gradual increase in mean blood-flow velocities illustrated a gradual perfusion during early reflow in both ICAs. On ischemia, the middle cerebral artery (MCA) territory presented a residual perfusion, whereas the caudal territory remained normally perfused. On reflow, speckle images showed a caudorostral propagation of reperfusion through anastomotic connections, and a reduced perfusion in the MCA territory. Autoradiography highlighted the caudorostral gradient, and persistent perfusion in ventral and medial regions. These blood-flow changes were accompanied by mitochondrial respiration impairment in the ipsilateral cortex. Collectively, these data indicate the presence of a primary collateral pathway through the circle of Willis, providing an immediate diversion of blood flow toward ischemic regions, and secondary efficient cortical anastomoses in the immature rat brain.

NASA-DoD Lower Process Temperature Lead-Free Solder Project Overview

NASA Technical Reports Server (NTRS)

Kessel, Kurt R.

2014-01-01

This project is a follow-on effort to the Joint Council on Aging AircraftJoint Group on Pollution Prevention (JCAAJG-PP) Pb-free Solder Project and NASA-DoD Lead-Free Electronics Project which were the first projects to test the reliability of Pb-free solder joints against the requirements of the aerospace and military community. This effort would continue to build on the results from the JCAAJG-PP Lead-Free Solder Project and NASA-DoD Lead-Free Electronics Project while focusing on a particular failure mechanism currently plaguing Pb-free assemblies, pad cratering.The NASA-DoD Lead-Free Electronics Project confirmed that pad cratering is one of the dominant failure modes that occur in various board level reliability tests, especially under dynamic loading. Pad Cratering is a latent defect that may occur during assembly, rework, and post assembly handling and testing.

Defect Inspection of Flip Chip Solder Bumps Using an Ultrasonic Transducer

PubMed Central

Su, Lei; Shi, Tielin; Xu, Zhensong; Lu, Xiangning; Liao, Guanglan

2013-01-01

Surface mount technology has spurred a rapid decrease in the size of electronic packages, where solder bump inspection of surface mount packages is crucial in the electronics manufacturing industry. In this study we demonstrate the feasibility of using a 230 MHz ultrasonic transducer for nondestructive flip chip testing. The reflected time domain signal was captured when the transducer scanning the flip chip, and the image of the flip chip was generated by scanning acoustic microscopy. Normalized cross-correlation was used to locate the center of solder bumps for segmenting the flip chip image. Then five features were extracted from the signals and images. The support vector machine was adopted to process the five features for classification and recognition. The results show the feasibility of this approach with high recognition rate, proving that defect inspection of flip chip solder bumps using the ultrasonic transducer has high potential in microelectronics packaging.

Solution-processed soldering of carbon nanotubes for flexible electronics.

PubMed

Rao, K D M; Radha, B; Smith, K C; Fisher, T S; Kulkarni, G U

2013-02-22

We report a simple lithography-free, solution-based method of soldering of carbon nanotubes with Ohmic contacts, by taking specific examples of multi-walled carbon nanotubes (MWNTs). This is achieved by self-assembling a monolayer of soldering precursor, Pd(2+) anchored to 1,10 decanedithiol, onto which MWNTs could be aligned across the gap electrodes via solvent evaporation. The nanosoldering was realized by thermal/electrical activation or by both in sequence. Electrical activation and the following step of washing ensure selective retention of MWNTs spanning across the gap electrodes. The soldered joints were robust enough to sustain strain caused during the bending of flexible substrates as well as during ultrasonication. The estimated temperature generated at the MWNT-Au interface using an electro-thermal model is ∼150 °C, suggesting Joule heating as the primary mechanism of electrical activation. Further, the specific contact resistance is estimated from the transmission line model.

SEM contour based metrology for microlens process studies in CMOS image sensor technologies

NASA Astrophysics Data System (ADS)

Lakcher, Amine; Ostrovsky, Alain; Le-Gratiet, Bertrand; Berthier, Ludovic; Bidault, Laurent; Ducoté, Julien; Jamin-Mornet, Clémence; Mortini, Etienne; Besacier, Maxime

2018-03-01

From the first digital cameras which appeared during the 70s to cameras of current smartphones, image sensors have undergone significant technological development in the last decades. The development of CMOS image sensor technologies in the 90s has been the main driver of the recent progresses. The main component of an image sensor is the pixel. A pixel contains a photodiode connected to transistors but only the photodiode area is light sensitive. This results in a significant loss of efficiency. To solve this issue, microlenses are used to focus the incident light on the photodiode. A microlens array is made out of a transparent material and has a spherical cap shape. To obtain this spherical shape, a lithography process is performed to generate resist blocks which are then annealed above their glass transition temperature (reflow). Even if the dimensions to consider are higher than in advanced IC nodes, microlenses are sensitive to process variability during lithography and reflow. A good control of the microlens dimensions is key to optimize the process and thus the performance of the final product. The purpose of this paper is to apply SEM contour metrology [1, 2, 3, 4] to microlenses in order to develop a relevant monitoring methodology and to propose new metrics to engineers to evaluate their process or optimize the design of the microlens arrays.

Quantifying Electromigration Processes in Sn-0.7Cu Solder with Lab-Scale X-Ray Computed Micro-Tomography

NASA Astrophysics Data System (ADS)

Mertens, James Charles Edwin

For decades, microelectronics manufacturing has been concerned with failures related to electromigration phenomena in conductors experiencing high current densities. The influence of interconnect microstructure on device failures related to electromigration in BGA and flip chip solder interconnects has become a significant interest with reduced individual solder interconnect volumes. A survey indicates that x-ray computed micro-tomography (muXCT) is an emerging, novel means for characterizing the microstructures' role in governing electromigration failures. This work details the design and construction of a lab-scale muXCT system to characterize electromigration in the Sn-0.7Cu lead-free solder system by leveraging in situ imaging. In order to enhance the attenuation contrast observed in multi-phase material systems, a modeling approach has been developed to predict settings for the controllable imaging parameters which yield relatively high detection rates over the range of x-ray energies for which maximum attenuation contrast is expected in the polychromatic x-ray imaging system. In order to develop this predictive tool, a model has been constructed for the Bremsstrahlung spectrum of an x-ray tube, and calculations for the detector's efficiency over the relevant range of x-ray energies have been made, and the product of emitted and detected spectra has been used to calculate the effective x-ray imaging spectrum. An approach has also been established for filtering 'zinger' noise in x-ray radiographs, which has proven problematic at high x-ray energies used for solder imaging. The performance of this filter has been compared with a known existing method and the results indicate a significant increase in the accuracy of zinger filtered radiographs. The obtained results indicate the conception of a powerful means for the study of failure causing processes in solder systems used as interconnects in microelectronic packaging devices. These results include the volumetric quantification of parameters which are indicative of both electromigration tolerance of solders and the dominant mechanisms for atomic migration in response to current stressing. This work is aimed to further the community's understanding of failure-causing electromigration processes in industrially relevant material systems for microelectronic interconnect applications and to advance the capability of available characterization techniques for their interrogation.

Platform technologies for hybrid optoelectronic integration and packaging

NASA Astrophysics Data System (ADS)

Datta, Madhumita

In order to bring fiber-optics closer to individual home and business services, the optical network components have to be inexpensive and reliable. Integration and packaging of optoelectronic devices holds the key to high-volume low-cost component manufacturing. The goal of this dissertation is to propose, study, and demonstrate various ways to integrate optoelectronic devices on a packaging platform to implement cost-effective, functional optical modules. Two types of hybrid integration techniques have been proposed: flip-chip solder bump bonding for high-density two-dimensional array packaging of surface-emitting devices, and solder preform bonding for fiber-coupled edge-emitting semiconductor devices. For flip-chip solder bump bonding, we developed a simple, inexpensive remetallization process called "electroless plating", which converts the aluminum bond pads of foundry-made complementary metal oxide semiconductor (CMOS) chips into solder-bondable and wire-bondable gold surfaces. We have applied for a patent on this remetallization technique. For fiber-pigtailed edge-emitting laser modules, we have studied the coupling characteristics of different types of lensed single-mode fibers including semispherically lensed fiber, cylindrically lensed fiber and conically lensed fiber. We have experimentally demonstrated 66% coupling efficiency with semispherically lensed fiber and 50% efficiency with conically lensed fibers. We have proposed and designed a packaging platform on which lensed fibers can be actively aligned to a laser and solder-attached reliably to the platform so that the alignment is retained. We have designed thin-film nichrome heaters on fused quartz platforms as local heat source to facilitate on-board solder alignment and attachment of fiber. The thermal performance of the heaters was simulated using finite element analysis tool ANSYS prior to fabrication. Using the heater's reworkability advantage, we have estimated the shift of the fiber due to solder shrinkage and introduced a pre-correction in the alignment process to restore optimum coupling efficiency close to 50% with conically lensed fibers. We have applied for a patent on this unique active alignment method through the University of Maryland's Technology Commercialization Office. Although we have mostly concentrated on active alignment platforms, we have proposed the idea of combining the passive alignment advantages of silicon optical benches to the on-board heater-assisted active alignment technique. This passive-active alignment process has the potential of cost-effective array packaging of edge-emitting devices.

Soldering tool heats workpieces and applies solder in one operation

NASA Technical Reports Server (NTRS)

Gudkese, V. W.

1966-01-01

Fountain-pen type soldering iron heats workpieces and applies solder to joints in densely packed electronics assemblies. The basic soldering tool is used with different-sized orifice tips, eliminating the need for an assortment of conventional soldering guns.

Analysis of Al diffusion processes in TiN barrier layers for the application in silicon solar cell metallization

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kumm, J.; Samadi, H.; Chacko, R. V.

An evaporated Al layer is known as an excellent rear metallization for highly efficient solar cells, but suffers from incompatibility with a common solder process. To enable solar cell-interconnection and module integration, in this work the Al layer is complemented with a solder stack of TiN/Ti/Ag or TiN/NiV/Ag, in which the TiN layer acts as an Al diffusion barrier. X-ray photoelectron spectroscopy measurements prove that diffusion of Al through the stack and the formation of an Al{sub 2}O{sub 3} layer on the stack's surface are responsible for a loss of solderability after a strong post-metallization anneal, which is often mandatorymore » to improve contact resistance and passivation quality. An optimization of the reactive TiN sputter process results in a densification of the TiN layer, which improves its barrier quality against Al diffusion. However, measurements with X-ray diffraction and scanning electron microscopy show that small grains with vertical grain boundaries persist, which still offer fast diffusion paths. Therefore, the concept of stuffing is introduced. By incorporating oxygen into the grain boundaries of the sputtered TiN layer, Al diffusion is strongly reduced as confirmed by secondary ion mass spectroscopy profiles. A quantitative analysis reveals a one order of magnitude lower Al diffusion coefficient for stuffed TiN layers. This metallization system maintains its solderability even after strong post-metallization annealing at 425 °C for 15 min. This paper thus presents an industrially feasible, conventionally solderable, and long-term stable metallization scheme for highly efficient silicon solar cells.« less

Design and Fabrication of Aspheric Microlens Array for Optical Read-Only-Memory Card System

NASA Astrophysics Data System (ADS)

Kim, Hongmin; Jeong, Gibong; Kim, Young‑Joo; Kang, Shinill

2006-08-01

An optical head based on the Talbot effect with an aspheric microlens array for an optical read-only-memory (ROM) card system was designed and fabricated. The mathematical expression for the wavefield diffracted by a periodic microlens array showed that the amplitude distribution at the Talbot plane from the focal plane of the microlens array was identically equal to that at the focal plane. To use a reflow microlens array as a master pattern of an ultraviolet-imprinted (UV-imprinted) microlens array, the reflow microlens was defined as having an aspheric shape. To obtain optical probes with good optical qualities, a microlens array with the minimum spherical aberration was designed by ray tracing. The reflow condition was optimized to realize the master pattern of a microlens with a designed aspheric shape. The intensity distribution of the optical probes at the Talbot plane from the focal plane showed a diffraction-limited shape.

Laser beam soldering of micro-optical components

NASA Astrophysics Data System (ADS)

Eberhardt, R.

2003-05-01

MOTIVATION Ongoing miniaturisation and higher requirements within optical assemblies and the processing of temperature sensitive components demands for innovative selective joining techniques. So far adhesive bonding has primarily been used to assemble and adjust hybrid micro optical systems. However, the properties of the organic polymers used for the adhesives limit the application of these systems. In fields of telecommunication and lithography, an enhancement of existing joining techniques is necessary to improve properties like humidity resistance, laserstability, UV-stability, thermal cycle reliability and life time reliability. Against this background laser beam soldering of optical components is a reasonable joining technology alternative. Properties like: - time and area restricted energy input - energy input can be controlled by the process temperature - direct and indirect heating of the components is possible - no mechanical contact between joining tool and components give good conditions to meet the requirements on a joining technology for sensitive optical components. Additionally to the laser soldering head, for the assembly of optical components it is necessary to include positioning units to adjust the position of the components with high accuracy before joining. Furthermore, suitable measurement methods to characterize the soldered assemblies (for instance in terms of position tolerances) need to be developed.

Soluble Lead and Bismuth Chalcogenidometallates: Versatile Solders for Thermoelectric Materials

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhang, Hao; Son, Jae Sung; Dolzhnikov, Dmitriy S.

Here we report the syntheses of largely unexplored lead and bismuth chalcogenidometallates in the solution phase. Using N2H4 as the solvent, new compounds such as K6Pb3Te6·7N2H4 were obtained. These soluble molecular compounds underwent cation exchange processes using resin chemistry, replacing Na+ or K+ by decomposable N2H5+ or tetraethylammonium cations. They also transformed into stoichiometric lead and bismuth chalcogenide nanomaterials with the addition of metal salts. Such a versatile chemistry led to a variety of composition-matched solders to join lead and bismuth chalcogenides and tune their charge transport properties at the grain boundaries. Solution-processed thin films composed of Bi0.5Sb1.5Te3 microparticles solderedmore » by (N2H5)6Bi0.5Sb1.5Te6 exhibited thermoelectric power factors (~28 μW/cm K2) comparable to those in vacuum-deposited Bi0.5Sb1.5Te3 films. The soldering effect can also be integrated with attractive fabrication techniques for thermoelectric modules, such as screen printing, suggesting the potential of these solders in the rational design of printable and moldable thermoelectrics.« less

The Effect of Gap Angle on Tensile Strength of Preceramic Base Metal Solder Joints

PubMed Central

Fattahi, Farnaz; Hashemi Ardakani, Zahra; Hashemi Ardakani, Maryam

2015-01-01

Statement of the Problem Soldering is a process commonly used in fabricating dental prosthesis. Since most soldered prosthesis fail at the solder joints; the joint strength is of utmost importance. Purpose The purpose of this study was to evaluate the effect of gap angle on the tensile strength of base metal solder joints. Materials and Method A total number of 40 Ni-Cr samples were fabricated according to ADA/ISO 9693 specifications for tensile test. Samples were cut at the midpoint of the bar, and were placed at the considered angles by employing an explicitly designed device. They were divided into 4 groups regarding the gap angle; Group C (control group) with parallel gap on steady distance of 0.2mm, Group 1: 10°, Group 2: 20°, and Group3: 30° gap angles. When soldered, the specimens were all tested for tensile strength using a universal testing machine at a cross-head speed of 0.5 mm/min with a preload of 10N. Kruskal-Wallis H test was used to compare tensile strength among the groups (p< 0.05). Results The mean tensile strength values obtained from the study groups were respectively 307.84, 391.50, 365.18, and 368.86 MPa. The tensile strength was not statistically different among the four groups in general (p≤ 0.490). Conclusion Making the gap angular at the solder joints and the subsequent unsteady increase of the gap distance would not change the tensile strength of the joint. PMID:26636118

Evaluation of Case Size 0603 BME Ceramic Capacitors

NASA Technical Reports Server (NTRS)

Teverovsky, Alexander A.

2015-01-01

High volumetric efficiency of commercial base metal electrode (BME) ceramic capacitors allows for a substantial reduction of weight and sizes of the parts compared to currently used military grade precious metal electrode (PME) capacitors. Insertion of BME capacitors in space applications requires a thorough analysis of their performance and reliability. In this work, six types of cases size 0603 BME capacitors from three vendors have been evaluated. Three types of multilayer ceramic capacitors (MLCCs) were designed for automotive industry and three types for general purposes. Leakage currents in the capacitors have been measured in a wide range of voltages and temperatures, and measurements of breakdown voltages (VBR) have been used to assess the proportion and severity of defects in the parts. The effect of soldering-related thermal shock stresses was evaluated by analysis of distributions of VBR for parts in 'as is' condition and after terminal solder dip testing at 350 C. Highly Accelerated Life Testing (HALT) at different temperatures was used to assess the activation energy of degradation of leakage currents and predict behavior of the parts at life test and normal operating conditions. To address issues related to rework and manual soldering, capacitors were soldered onto different substrates at different soldering conditions. The results show that contrary to a common assumption that large-size capacitors are mostly vulnerable to soldering stresses, cracking in small size capacitors does happen unless special measures are taken during assembly processes.

Closure of skin incisions in rabbits by laser soldering: I: Wound healing pattern.

PubMed

Simhon, David; Brosh, Tamar; Halpern, Marisa; Ravid, Avi; Vasilyev, Tamar; Kariv, Naam; Katzir, Abraham; Nevo, Zvi

2004-01-01

Temperature-controlled tissue laser soldering is an innovative sutureless technique awaiting only solid experimental data to become the gold-standard surgical procedure for incision closure. The goals of the current study were: (1) to define the optimal laser soldering conditions, (2) to explore the immediate skin reparative healing events after sealing the wound, and (3) to determine the long-term trajectory of skin wound healing. Skin incisions were generated over rabbit dorsa and were closed using different wound-closure interventions, in three groups: (a) closure, using a temperature-controlled infrared fiberoptic CO2 laser system, employing 47% bovine serum albumin as a solder; (b) wound closure by cyanoacrylate glues; and (c) wound closure by sutures. The reparative outcomes were evaluated macroscopically and microscopically, employing semi-quantitative grading indices. Laser soldering of incisions at T = 65 degrees C emerged as the optimal method achieving immediate wound sealing. This in turn induced accelerated reparative events characterized by a reduced inflammatory reaction, followed by minimal scarring and leading to a fine quality healing. Temperature-controlled laser soldering offers an accelerated wound reparative process with numerous advantages over the conventional methods. Further investigations may reveal additional benefits in the spectrum of advantages that this innovative surgical technology has to offer. This can introduce new scientific insight that will pave the way for clinical use.

Fluxless eutectic bonding of GaAs-on-Si by using Ag/Sn solder

NASA Astrophysics Data System (ADS)

Eo, Sung-Hwa; Kim, Dae-Seon; Jeong, Ho-Jung; Jang, Jae-Hyung

2013-11-01

Fluxless GaAs-on-Si wafer bonding using Ag/Sn solder was investigated to realize uniform and void-free heterogeneous material integration. The effects of the diffusion barrier, Ag/Sn thickness, and Ar plasma treatment were studied to achieve the optimal fluxless bonding process. Pt on a GaAs wafer and Mo on a Si wafer act as diffusion barriers by preventing the flow of Ag/Sn solder into both the wafers. The bonding strength is closely related to the Ag/Sn thickness and Ar plasma treatment. A shear strength test was carried out to investigate the bonding strength. Under identical bonding conditions, the Ag/Sn thickness was optimized to achieve higher bonding strength and to avoid the formation of voids due to thermal stress. An Ar plasma pretreatment process improved the bonding strength because the Ar plasma removed carbon contaminants and metal-oxide bonds from the metal surface.

Characterization of Low-Melting-Point Sn-Bi-In Lead-Free Solders

NASA Astrophysics Data System (ADS)

Li, Qin; Ma, Ninshu; Lei, YongPing; Lin, Jian; Fu, HanGuang; Gu, Jian

2016-11-01

Development of lead-free solders with low melting temperature is important for substitution of Pb-based solders to reduce direct risks to human health and the environment. In the present work, Sn-Bi-In solders were studied for different ratios of Bi and Sn to obtain solders with low melting temperature. The microstructure, thermal properties, wettability, mechanical properties, and reliability of joints with Cu have been investigated. The results show that the microstructures of the Sn-Bi-In solders were composed of β-Sn, Bi, and InBi phases. The intermetallic compound (IMC) layer was mainly composed of Cu6Sn5, and its thickness increased slightly as the Bi content was increased. The melting temperature of the solders was around 100°C to 104°C. However, when the Sn content exceeded 50 wt.%, the melting range became larger and the wettability became worse. The tensile strength of the solder alloys and solder joints declined with increasing Bi content. Two fracture modes (IMC layer fracture and solder/IMC mixed fracture) were found in solder joints. The fracture mechanism of solder joints was brittle fracture. In addition, cleavage steps on the fracture surface and coarse grains in the fracture structure were comparatively apparent for higher Bi content, resulting in decreased elongation for both solder alloys and solder joints.

Development of Cu Clad Cu-Zr Based Metallic Glass and Its Solderability

NASA Astrophysics Data System (ADS)

Terajima, Takeshi; Kimura, Hisamichi; Inoue, Akihisa

Soldering is a candidate technique for joining metallic glasses. It can be processed far below the crystallization temperatures of the various metallic glasses so that there is no possibility of crystallization. However, wettability of Cu-Zr based metallic glass by Pb free solder is poor because a strong surface oxide film interferes direct contact between them. To overcome the problem, Cu thin film clad metallic glass was developed. It was preliminary produced by casting a melt of Cu36Zr48Al8Ag8 pre-alloy into Cu mold cavity, inside which Cu thin film with 2 mm in thickness was set on the wall. Cu36Zr48Al8Ag8 metallic glass, whose surface Cu thin film was welded to, was successfully produced. From the microstructure analyses, it was found that reaction layer was formed at the interface between Cu and Cu36Zr48Al8Ag8 metallic glass, however, there was no oxide in the Cu clad layer. Solderability to the metallic glass was drastically increased. The Cu clad layer played an important role to prevent the formation of surface oxide film and consequently improved the solderability.

Effects of limited cu supply on soldering reactions between SnAgCu and Ni

NASA Astrophysics Data System (ADS)

Ho, C. E.; Lin, Y. W.; Yang, S. C.; Kao, C. R.; Jiang, D. S.

2006-05-01

The volume difference between the various types of solder joints in electronic devices can be enormous. For example, the volume difference between a 760-µm ball grid array solder joint and a 75-µm flip-chip solder joint is as high as 1000 times. Such a big difference in volume produces a pronounced solder volume effect. This volume effect on the soldering reactions between the Sn3AgxCu (x=0.4, 0.5, or 0.6 wt.%) solders and Ni was investigated. Three different sizes of solder spheres (300, 500, and 760 µm in diameter) were soldered onto Ni soldering pads. Both the Cu concentration and the solder volume had a strong effect on the type of the reaction products formed. In addition, (Cu,Ni)6Sn5 massively spalled from the interface under certain conditions, including smaller joints and those with lower Cu concentration. We attributed the massive spalling of (Cu,Ni)6Sn5 to the decrease of the available Cu in the solders. The results of this study suggest that Cu-rich SnAgCu solders can be used to prevent this massive spalling.

[The importance of the thermometric method for assessing the function of mucoperiosteal flaps in uranostaphyloplasty with/without transection of the neurovascular bundles in the rehabilitation of patients with congenital cleft palate].

PubMed

Bernadskiĭ, Iu I; Khar'kov, L V; Prudnikov, V M

1990-01-01

The nature and degree of reflow to the mucoperiosteal flaps was evaluated using a distant thermometry of the cleft palate in 67 children under uranostaphyloplasty and in early postsurgical period. In extracting the neurovascular bundles from their channels heat reflow to the palate was more fast and pronounced than with the bundles sectioned.

Process for electrically interconnecting electrodes

DOEpatents

Carey, Paul G.; Thompson, Jesse B.; Colella, Nicolas J.; Williams, Kenneth A.

2002-01-01

Electrical interconnects for solar cells or other electronic components using a silver-silicone paste or a lead-tin (Pb--Sn) no-clean fluxless solder cream, whereby the high breakage of thin (<6 mil thick) solar cells using conventional solder interconnect is eliminated. The interconnects of this invention employs copper strips which are secured to the solar cells by a silver-silicone conductive paste which can be used at room temperature, or by a Pb--Sn solder cream which eliminates undesired residue on the active surfaces of the solar cells. Electrical testing using the interconnects of this invention has shown that no degradation of the interconnects developed under high current testing, while providing a very low contact resistance value.

Effect of Solder-Joint Geometry on the Low-Cycle Fatigue Behavior of Sn- xAg-0.7Cu

NASA Astrophysics Data System (ADS)

Lee, Hwa-Teng; Huang, Kuo-Chen

2016-12-01

Low-cycle fatigue tests of Sn-Ag-Cu (SAC) Pb-free solder joints under fixed displacement were performed to evaluate the influence of Ag content (0-3 wt.%) and solder-joint geometry (barrel and hourglass types) on solder-joint fatigue behavior and reliability. The solder joints were composed of fine particles of Ag3Sn and Cu6Sn5, which aggregated as an eutectic constituent at grain boundaries of the primary β-Sn phase and formed a dense network structure. A decrease in the Ag content resulted in coarsening of the β-Sn and eutectic phases, which, in turn, decreased the strength of the joint and caused earlier failure. Solder joints in the hourglass form exhibited better fatigue performance with longer life than barrel-type joints. The sharp contact angle formed between the solder and the Cu substrate by the barrel-type joints concentrated stress, which compromised fatigue reliability. The addition of Ag to the solder, however, enhanced fatigue performance because of strengthening caused by Ag3Sn formation. The cracks of the barrel-type SAC solder joints originated mostly at the contact corner and propagated along the interfacial layer between the interfacial intermetallic compound (IMC) and solder matrix. Hourglass-type solder joints, however, demonstrated both crack initiation and propagation in the solder matrix (solder mode). The addition of 1.5-2.0 wt.% Ag to SAC solder appears to enhance the fatigue performance of solder joints while maintaining sufficient strength.

The effect of micro alloying on the microstructure evolution of Sn-Ag-Cu lead-free solder

NASA Astrophysics Data System (ADS)

Werden, Jesse

The microelectronics industry is required to obtain alternative Pb-free soldering materials due to legal, environmental, and technological factors. As a joining material, solder provides an electrical and mechanical support in electronic assemblies and therefore, the properties of the solder are crucial to the durability and reliability of the solder joint and the function of the electronic device. One major concern with new Pb-free alternatives is that the microstructure is prone to microstructural coarsening over time which leads to inconsistent properties over the device's lifetime. Power aging the solder is a common method of stabilizing the microstructure for Pb-based alloys, however, it is unclear if this will be an appropriate solution to the microstructural coarsening of Pb-free solders. The goal of this work is to develop a better understanding of the coarsening process in new solder alloys and to suggest methods of stabilizing the solder microstructure. Microalloying is one potential solution to the microstructural coarsening problem. This experiment consists of a microstructural coarsening study of SAC305 in which each sample has been alloyed with one of three different solutes, directionally solidified at 100microm/s, and then aged at three different temperatures over a total period of 20 days. There are several important conclusions from this experiment. First, the coarsening kinetics of the intermetallics in the ternary eutectic follow the Ostwald ripening model where r3 in proprotional to t for each alloying constituent. Second, the activation energy for coarsening was found to be 68.1+/-10.3 kJ/mol for the SAC305 samples, Zn had the most significant increase in the activation energy increasing it to 88.8+/-34.9 kJ/mol for the SAC+Zn samples, Mn also increased the activation energy to 83.2+/-20.8 kJ/mol for the SAC+Mn samples, and Sb decreased the activation energy to 48.0+/-3.59 kJ/mol for the SAC+Sb samples. Finally, it was found that the coarsening kinetics of SAC305, SAC+Zn, SAC+Mn, and SAC+Sb are all much slower than Pb-Sn alloys, therefore, power aging the solder will not be a viable method of stabilizing the microstructure. However, adding small amounts of Zn or Mn may be useful to maintain the original microstructure so that power aging is not required.

Novel solid protein solder designs for laser-assisted tissue repair.

PubMed

McNally, K M; Sorg, B S; Welch, A J

2000-01-01

Previous studies have shown that the application of chromophore-enhanced albumin protein solders to augment laser tissue repairs significantly improves repair strength, enhances edge co-optation, and reduces thermal tissue injury. These investigations are furthered with this in vitro study conducted to assess a new range of specially designed chromophore-enhanced solid protein solders manufactured and tested for application during laser-assisted tissue repair. The experimental study was divided into three parts. In the first part of the study, the creation of a chromophore concentration gradient across the thickness of the solid protein solder was investigated as a means to improve control of the heat source gradient through the solder during laser irradiation. In the second part of the study, predenaturation of the solid protein solder was investigated as a means for enhancing the stability of the solder in physiological fluids before irradiation. Finally, in the third part of the study, the feasibility of using synthetic polymers as a scaffold for traditional albumin protein solder mixes was investigated as a means of improving the flexibility of the solder. Uniform denaturation across the thickness of the solder was achieved by controlling the chromophore concentration gradient, thus ensuring stable solder-tissue fusion when the specimen was submerged in a hydrated environment. Predenaturation of the solid protein solder significantly reduced the solubility of the solder, and consequently, improved the handling characteristics of the solder. The solder-doped polymer membranes were flexible enough to be wrapped around tissue, whereas their solid nature avoided problems associated with "runaway" of the less viscous liquid solders currently used by researchers. In addition, the solder-doped polymer membranes could be easily tailored to a wide range of geometries suitable to many clinical applications. The novel solid protein solder designs presented here add a new dimension to tissue repair as their flexible, moldable, and absorption controllable nature, greatly improves the clinical applicability of laser-assisted tissue repair. Copyright 2000 Wiley-Liss, Inc.

Electromigration in solder joints and solder lines

NASA Astrophysics Data System (ADS)

Gan, H.; Choi, W. J.; Xu, G.; Tu, K. N.

2002-06-01

Electromigration may affect the reliability of flip-chip solder joints. Eutectic solder is a two-phase alloy, so its electromigration behavior is different from that in aluminum or copper interconnects. In addition, a flipchip solder joint has a built-in currentcrowding configuration to enhance electromigration failure. To better understand electromigration in SnPb and lead-free solder alloys, the authors prepared solder lines in v-grooves etched on Si (001). This article discusses the results of those tests and compares the electromigration failure modes of eutectic SnPb and SnAgCu flip-chip solder joints along with the mean-timeto-failure.

NTF: Soldering Technology Development for Cryogenics

NASA Technical Reports Server (NTRS)

Hall, E. T., Jr.

1985-01-01

The advent of the National Transonic Facility (NTF) brought about a new application for an old joining method, soldering. Soldering for use at cryogenic temperatures requires that solders remain ductile and free from tin-pest (grey tin), have toughness to withstand aerodynamic loads associated with flight research, and maintain their surface finishes. Solders are used to attach 347 Stainless-Steel tubing in surface grooves of models. The solder must fill up the gap and metallurgically bound to the tubing and model. Cryogenic temperatures require that only specific materials for models can be used, including: Vasco Max 200 CVM, lescalloy A-286 Vac Arc, pH 13-8 Mo. Solders identified for testing at this time are: 50% Sn - 49.5% Pb - 0.5% Sb, 95% Sn - 5% Sb, 50% In 50% Pb, and 37.5% Sn - 37.5% Pb - 25% In. With these materials and solders, it is necessary to determine their solderability. After solderability is determined, tube/groove specimens are fabricated and stressed under cryogenic temperatures. Compatible solders are then used for acutual models.

Vertically aligned multiwalled carbon nanotubes as electronic interconnects

NASA Astrophysics Data System (ADS)

Gopee, Vimal Chandra

The drive for miniaturisation of electronic circuits provides new materials challenges for the electronics industry. Indeed, the continued downscaling of transistor dimensions, described by Moore’s Law, has led to a race to find suitable replacements for current interconnect materials to replace copper. Carbon nanotubes have been studied as a suitable replacement for copper due to its superior electrical, thermal and mechanical properties. One of the advantages of using carbon nanotubes is their high current carrying capacity which has been demonstrated to be three orders of magnitude greater than that of copper. Most approaches in the implementation of carbon nanotubes have so far focused on the growth in vias which limits their application. In this work, a process is described for the transfer of carbon nanotubes to substrates allowing their use for more varied applications. Arrays of vertically aligned multiwalled carbon nanotubes were synthesised by photo-thermal chemical vapour deposition with high growth rates. Raman spectroscopy was used to show that the synthesised carbon nanotubes were of high quality. The carbon nanotubes were exposed to an oxygen plasma and the nature of the functional groups present was determined using X-ray photoelectron spectroscopy. Functional groups, such as carboxyl, carbonyl and hydroxyl groups, were found to be present on the surface of the multiwalled carbon nanotubes after the functionalisation process. The multiwalled carbon nanotubes were metallised after the functionalisation process using magnetron sputtering. Two materials, solder and sintered silver, were chosen to bind carbon nanotubes to substrates so as to enable their transfer and also to make electrical contact. The wettability of solder to carbon nanotubes was investigated and it was demonstrated that both functionalisation and metallisation were required in order for solder to bond with the carbon nanotubes. Similarly, functionalisation followed by metallisation was critical for bonding carbon nanotubes to sintered silver. A step by step process is described that allows the production of solder-carbon nanotubes and silver-carbon nanotubes interconnects. 4-point probe electrical characterisation of the interconnects was performed and the interconnects were shown to have a resistivity of 5.0 x 10-4 Ωcm for solder-carbon nanotubes and 5.2 x 10-4 Ωcm for silver-carbon nanotubes interconnects. Ramp to failure tests carried out on solder-carbon nanotubes interconnects showed current carrying capacity of 0.75 MA/cm2, only one order of magnitude lower than copper.

Tool and Fixture Design

DOE Office of Scientific and Technical Information (OSTI.GOV)

Graham, Mark W.

2015-07-28

In a manufacturing process, a need is identified and a product is created to fill this need. While design and engineering of the final product is important, the tools and fixtures that aid in the creation of the final product are just as important, if not more so. Power supplies assembled at the TA-55 PF-5 have been designed by an excellent engineering team. The task in PF-5 now is to ensure that all steps of the assembly and manufacturing process can be completed safely, reliably, and in a quality repeatable manner. One of these process steps involves soldering fine wiresmore » to an electrical connector. During the process development phase, the method of soldering included placing the power supply in a vice in order to manipulate it into a position conducive to soldering. This method is unacceptable from a reliability, repeatability, and ergonomic standpoint. To combat these issues, a fixture was designed to replace the current method. To do so, a twelve step engineering design process was used to create the fixture that would provide a solution to a multitude of problems, and increase the safety and efficiency of production.« less

Comparison of implant-abutment interface misfits after casting and soldering procedures.

PubMed

Neves, Flávio Domingues das; Elias, Gisele Araújo; da Silva-Neto, João Paulo; de Medeiros Dantas, Lucas Costa; da Mota, Adérito Soares; Neto, Alfredo Júlio Fernandes

2014-04-01

The aim of this study was to compare vertical and horizontal adjustments of castable abutments after conducting casting and soldering procedures. Twelve external hexagonal implants (3.75 × 10 mm) and their UCLA abutments were divided according their manufacturer and abutment type: PUN (plastic UCLA, Neodent), PUC (plastic UCLA, Conexão), PU3i (plastic UCLA, Biomet 3i), and PUTN (plastic UCLA with Tilite milled base, Neodent). Three infrastructures of a fixed partial implant-supported bridge with 3 elements were produced for each group. The measurements of vertical (VM) and horizontal (HM) misfits were obtained via scanning electron microscopy after completion of casting and soldering. The corresponding values were determined to be biomechanically acceptable to the system, and the results were rated as a percentage. Statistical analysis establishes differences between groups by chi-square after procedures, and McNeman's test was applied to analyze the influence of soldering over casting (α ≤ .05). For the values of VM and HM, respectively, when the casting process was complete, it was observed that 83.25% and 100% (PUTN), 33.3% and 27.75% (PUN), 33.3% and 88.8% (PUC), 33.3% and 94.35% (PU3i) represented acceptable values. After completing the requisite soldering, acceptable values were 50% and 94.35% (PUTN), 16.6% and 77.7% (PUN), 38.55% and 77.7% (PUC), and 27.75% and 94.35% (PU3i). Within the limitations of this study, it can be concluded that the premachined abutments presented more acceptable VM values. The HM values were within acceptable limits before and after the soldering procedure for most groups. Further, the soldering procedure resulted in an increase of VM in all groups.

Limitation of Infarct Size and No-Reflow by Intracoronary Adenosine Depends Critically on Dose and Duration.

PubMed

Yetgin, Tuncay; Uitterdijk, André; Te Lintel Hekkert, Maaike; Merkus, Daphne; Krabbendam-Peters, Ilona; van Beusekom, Heleen M M; Falotico, Robert; Serruys, Patrick W; Manintveld, Olivier C; van Geuns, Robert-Jan M; Zijlstra, Felix; Duncker, Dirk J

2015-12-28

In the absence of effective clinical pharmacotherapy for prevention of reperfusion-mediated injury, this study re-evaluated the effects of intracoronary adenosine on infarct size and no-reflow in a porcine model of acute myocardial infarction using clinical bolus and experimental high-dose infusion regimens. Despite the clear cardioprotective effects of adenosine, when administered prior to ischemia, studies on cardioprotection by adenosine when administered at reperfusion have yielded contradictory results in both pre-clinical and clinical settings. Swine (54 ± 1 kg) were subjected to a 45-min mid-left anterior descending artery occlusion followed by 2 h of reperfusion. In protocol A, an intracoronary bolus of 3 mg adenosine injected over 1 min (n = 5) or saline (n = 10) was administered at reperfusion. In protocol B, an intracoronary infusion of 50 μg/kg/min adenosine (n = 15) or saline (n = 21) was administered starting 5 min prior to reperfusion and continued throughout the 2-h reperfusion period. In protocol A, area-at-risk, infarct size, and no-reflow were similar between groups. In protocol B, risk zones were similar, but administration of adenosine resulted in significant reductions in infarct size from 59 ± 3% of the area-at-risk in control swine to 46 ± 4% (p = 0.02), and no-reflow from 49 ± 6% of the infarct area to 26 ± 6% (p = 0.03). During reperfusion, intracoronary adenosine can limit infarct size and no-reflow in a porcine model of acute myocardial infarction. However, protection was only observed when adenosine was administered via prolonged high-dose infusion, and not via short-acting bolus injection. These findings warrant reconsideration of adenosine as an adjuvant therapy during early reperfusion. Copyright © 2015 American College of Cardiology Foundation. Published by Elsevier Inc. All rights reserved.

Recovery of materials from waste printed circuit boards by vacuum pyrolysis and vacuum centrifugal separation.

PubMed

Zhou, Yihui; Wu, Wenbiao; Qiu, Keqiang

2010-11-01

In this research, a two-step process consisting of vacuum pyrolysis and vacuum centrifugal separation was employed to treat waste printed circuit boards (WPCBs). Firstly, WPCBs were pyrolysed under vacuum condition at 600 °C for 30 min in a lab-scale reactor. Then, the obtained pyrolysis residue was heated under vacuum until the solder was melted, and then the molten solder was separated from the pyrolysis residue by the centrifugal force. The results of vacuum pyrolysis showed that the type-A of WPCBs (the base plates of which was made from cellulose paper reinforced phenolic resin) pyrolysed to form an average of 67.97 wt.% residue, 27.73 wt.% oil, and 4.30 wt.% gas; and pyrolysis of the type-B of WPCBs (the base plates of which was made from glass fiber reinforced epoxy resin) led to an average mass balance of 72.20 wt.% residue, 21.45 wt.% oil, and 6.35 wt.% gas. The results of vacuum centrifugal separation showed that the separation of solder was complete when the pyrolysis residue was heated at 400 °C, and the rotating drum was rotated at 1200 rpm for 10 min. The pyrolysis oil and gas can be used as fuel or chemical feedstock after treatment. The pyrolysis residue after solder separation contained various metals, glass fibers and other inorganic materials, which could be recycled for further processing. The recovered solder can be reused directly and it can also be a good resource of lead and tin for refining. Copyright © 2010 Elsevier Ltd. All rights reserved.

Vacuum encapsulated, high temperature diamond amplified cathode capsule and method for making same

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rao, Triveni; Walsh, Josh; Gangone, Elizabeth

2015-12-29

A vacuum encapsulated, hermetically sealed cathode capsule for generating an electron beam of secondary electrons, which generally includes a cathode element having a primary emission surface adapted to emit primary electrons, an annular insulating spacer, a diamond window element comprising a diamond material and having a secondary emission surface adapted to emit secondary electrons in response to primary electrons impinging on the diamond window element, a first high-temperature solder weld disposed between the diamond window element and the annular insulating spacer and a second high-temperature solder weld disposed between the annular insulating spacer and the cathode element. The cathode capsulemore » is formed by a high temperature weld process under vacuum such that the first solder weld forms a hermetical seal between the diamond window element and the annular insulating spacer and the second solder weld forms a hermetical seal between the annular spacer and the cathode element whereby a vacuum encapsulated chamber is formed within the capsule.« less

Current Space Station Experiments Investigating Component Level Electronics Repair

NASA Technical Reports Server (NTRS)

Easton, John W.; Struk, Peter M.

2010-01-01

The Soldering in a Reduced Gravity Experiment (SoRGE) and Component Repair Experiment (CRE)-1 are tests performed on the International Space Station to determine the techniques, tools, and training necessary to allow future crews to perform manual electronics repairs at the component level. SoRGE provides information on the formation and internal structure of through-hole solder joints, illustrating the challenges and implications of soldering in reduced gravity. SoRGE showed a significant increase in internal void defects for joints formed in low gravity compared to normal gravity. Methods for mitigating these void defects were evaluated using a modified soldering process. CRE-1 demonstrated the removal, cleaning, and replacement of electronics components by manual means on functional circuit boards. The majority of components successful passed a post-repair functional test demonstrating the feasibility of component-level repair within the confines of a spacecraft. Together, these tasks provide information to recommend material and tool improvements, training improvements, and future work to help enable electronics repairs in future space missions.

Multiwire conductor having increased interwire resistance and good mechanical stability and method for making same

DOEpatents

Luhman, Thomas; Klamut, Carl

1984-02-14

An improved multiwire conductor of the type which is mechanically stabilized by a solder filler. A solder filled conductor is heated to a temperature sufficient to make the solder brittle, but below the melting point of the solder. While still hot, the conductor is flexed, causing the solder to separate from the wires comprising the conductor, thereby increasing the interwire resistance. In one embodiment the conductor may be heated to a temperature above the eutectic temperature of the solder so that a controlled amount of solder is removed. The subject invention is particularly suited for use with braided, ribbon-type, solder filled superconductors.

Multiwire conductor having increased interwire resistance and good mechanical stability and method for making same

DOEpatents

Luhman, T.; Klamut, C.

1982-03-15

An improved multiwire conductor of the type which is mechanically stabilized by a solder filler. A solder filled conductor is heated to a temperature sufficient to make the solder brittle, but below the melting point of the solder. While still hot, the conductor is flexed, causing the solder to separate from the wires comprising the conductor, thereby increasing the interwire resistance. In one embodiment the conductor may be heated to a temperature above the eutectic temperature of the solder so that a controlled amount of solder is removed. The subject invention is particularly suited for use with braided, ribbon-type, solder filled superconductors.

Effect of Epoxy on Mechanical Property of SAC305 Solder Joint with Various Surface Finishes Under 3-Point Bend Test.

PubMed

Jeong, Haksan; Myung, Woo-Ram; Sung, Yong-Gue; Kim, Kyung-Yeol; Jung, Seung-Boo

2018-09-01

Microstructures and mechanical property of Sn-3.0Ag-0.5Cu (SAC305) and epoxy Sn-3.0Ag-0.5Cu (epoxy SAC) solder joints were investigated with various surface finishes; organic solderability preservative (OSP), electroless nickel immersion gold (ENIG) and electroless nickel electroless palladium immersion gold (ENEPIG). Bending property of solder joints was evaluated by 3-point bend test method. Microstructure and chemical composition of solder joints was characterized by scanning electron microscope (SEM) and energy dispersive X-ray spectroscopy (EDX), respectively. Epoxy did not effect on intermetallic compound (IMC) morphology. Scalloped shaped Cu6Sn5 IMC was observed at OSP surface finish. Chunky-like shaped and needle-like shaped (Ni,Cu)6Sn5 IMC were observed at the solder/ENIG joint and solder/ENEPIG joint, respectively. The bending cycles of SAC305/OSP joint, SAC305/ENIG joints and SAC305/ENEPIG joints were 720, 440 and 481 cycle numbers. The bending cycles of epoxy SAC and three types surface finished solder joints were over 1000 bending cycles. Under OSP surface finish, bending cycles of epoxy SAC solder was approximately 1.5 times higher than those of SAC305 solder joint. Bending cycles of epoxy SAC solder was over twice times higher than those of SAC305 solder with ENIG and ENEPIG surface finishes. The bending property of epoxy solder joint was enhanced due to epoxy fillet held the solder joint.

Investigation of the interaction of the solder components for laser welding of biological tissues

NASA Astrophysics Data System (ADS)

Ryabki, Dmitrii I.; Gerasimenko, Alexander Yu.; Kvasnov, Bogdan A.; Pyankov, Evgeny S.; Pyanov, Ivan V.; Telyshev, Dmitry V.; Podgaetsky, Vitaly M.

2017-07-01

Increase the weld strength is main directions of development of laser welding technology. Laser solders are used to increase tensile strength of welds and reduce of tissue temperature necrosis. Soldering components interaction effect the solder tensile strength characteristics of laser welds. Tensile strengths for welds obtained using of solder various concentration BSA and SWCNT was measured. Dimensions laser solder aggregates were measured. The dependence between the dimensions of the aggregates of laser solder and the tensile strength of the weld has been revealed.

Repair strength dependence on solder protein concentration: a study in laser tissue-welding.

PubMed

Lauto, A

1998-01-01

A novel laser-activated solid solder has been coupled with a diode laser to investigate the dependence of the solder protein concentration on the tensile strength of the soldered tissues. The uncertainty of laser welding, due to the fluid glue, was overcome using the solid solder. Sixty-two severed rat tibial nerves and vas deferens were repaired using rectangular protein bands with two different albumin concentrations (58% and 68% by weight). The laser power (90 mW and 140 mW), dose (12.9 +/- 0.7 J/mg, mean +/- s.d.), and solder dimensions (thickness = 0.15 +/- 0.01 mm, surface area = 7.8 +/- 0.4 mm2) were kept constant during the operations. The laser welds with high protein solder concentration were significantly (P < 0.05) stronger (28 +/- 3.5 g) than the welds with low protein solder concentration (23 +/- 5 g). The average tensile strength of the laser soldered tissues increased as the protein solder concentration increased.

Diode Lasers used in Plastic Welding and Selective Laser Soldering - Applications and Products

NASA Astrophysics Data System (ADS)

Reinl, S.

Aside from conventional welding methods, laser welding of plastics has established itself as a proven bonding method. The component-conserving and clean process offers numerous advantages and enables welding of sensitive assemblies in automotive, electronic, medical, human care, food packaging and consumer electronics markets. Diode lasers are established since years within plastic welding applications. Also, soft soldering using laser radiation is becoming more and more significant in the field of direct diode laser applications. Fast power controllability combined with a contactless temperature measurement to minimize thermal damage make the diode laser an ideal tool for this application. These advantages come in to full effect when soldering of increasingly small parts in temperature sensitive environments is necessary.

Laser tissue welding mediated with a protein solder

NASA Astrophysics Data System (ADS)

Small, Ward, IV; Heredia, Nicholas J.; Celliers, Peter M.; Da Silva, Luiz B.; Eder, David C.; Glinsky, Michael E.; London, Richard A.; Maitland, Duncan J.; Matthews, Dennis L.; Soltz, Barbara A.

1996-05-01

A study of laser tissue welding mediated with an indocyanine green dye-enhanced protein solder was performed. Freshly obtained sections of porcine artery were used for the experiments. Sample arterial wall thickness ranged from two to three millimeters. Incisions approximately four millimeters in length were treated using an 805 nanometer continuous- wave diode laser coupled to a one millimeter diameter fiber. Controlled parameters included the power delivered by the laser, the duration of the welding process, and the concentration of dye in the solder. A two-color infrared detection system was constructed to monitor the surface temperatures achieved at the weld site. Burst pressure measurements were made to quantify the strengths of the welds immediately following completion of the welding procedure.

Highly stretchable and conductive silver nanowire thin films formed by soldering nanomesh junctions.

PubMed

Chen, Shih-Pin; Liao, Ying-Chih

2014-10-07

Silver nanowires (AgNWs) have been widely used for stretchable and foldable conductors due to their percolating network nanostructure. To enhance the mechanical strength of AgNW thin films under extreme stretching conditions, in this study, we utilize a simple chemical reaction to join AgNW network connections. Upon applying a reactive ink over AgNW thin films, silver nanoparticles are preferentially generated over the nanowire junctions and solder the nanomesh structures. The soldered nanostructure reinforces the conducting network and exhibits no obvious change in electrical conductivity in the stretching or rolling process with elongation strains up to 120%. Several examples are also demonstrated to show potential applications of this material in stretchable electronic devices.

Reliable high-power diode lasers: thermo-mechanical fatigue aspects

NASA Astrophysics Data System (ADS)

Klumel, Genady; Gridish, Yaakov; Szafranek, Igor; Karni, Yoram

2006-02-01

High power water-cooled diode lasers are finding increasing demand in biomedical, cosmetic and industrial applications, where repetitive cw (continuous wave) and pulsed cw operation modes are required. When operating in such modes, the lasers experience numerous complete thermal cycles between "cold" heat sink temperature and the "hot" temperature typical of thermally equilibrated cw operation. It is clearly demonstrated that the main failure mechanism directly linked to repetitive cw operation is thermo-mechanical fatigue of the solder joints adjacent to the laser bars, especially when "soft" solders are used. Analyses of the bonding interfaces were carried out using scanning electron microscopy. It was observed that intermetallic compounds, formed already during the bonding process, lead to the solders fatigue both on the p- and n-side of the laser bar. Fatigue failure of solder joints in repetitive cw operation reduces useful lifetime of the stacks to hundreds hours, in comparison with more than 10,000 hours lifetime typically demonstrated in commonly adopted non-stop cw reliability testing programs. It is shown, that proper selection of package materials and solders, careful design of fatigue sensitive parts and burn-in screening in the hard pulse operation mode allow considerable increase of lifetime and reliability, without compromising the device efficiency, optical power density and compactness.

Garlicin attenuates reperfusion no-reflow in a catheter-based porcine model of acute myocardial infarction.

PubMed

Peng, Yang; Jiahui, Li; Aili, Li; Yong, Wang; Zaixiang, Shi; Yuannan, Ke; Xianlun, Li

2012-08-01

To evaluate whether garlicin can attenuate reperfusion no-reflow in a catheter-based porcine model of acute myocardial infarction (AMI). Twenty-two swine were used: six in a sham-operation group, and eight each in the control and garlicin groups. The distal part of the left anterior descending coronary artery (LAD) in the latter two groups was occluded by a dilated balloon for 2 hr, then reperfused for 3 hr. Garlicin (1.88mg/kg) was injected just before reperfusion until reperfusion for 1 hr in the garlicin group. Hemodynamic data were examined before AMI, 2 hr after occlusion, and 3 hr after reperfusion. Myocardial contrast echocardiography (MCE) and pathological staining were performed to evaluate the myocardial no-reflow area (NRA). Serum proinflammatory cytokines and endothelin (ET)-1 were examined by radioimmunoassay. Left ventricular systolic pressure (LVSP) and left ventricular end-diastolic pressure (LVEDP) significantly improved in the garlicin group after reperfusion compared with the control group and also 2hr after AMI (p<0.05 for both). MCE and pathological staining both showed garlicin attenuated reperfusion NRA after AMI (p<0.05, p<0.01). Garlicin not only decreased serum interleukin (IL)-6 and tumor necrosis factor (TNF)-α after reperfusion (p<0.05 for both), but also ET-1 level (p<0.01). Garlicin attenuated reperfusion no-reflow in our catheter-based porcrine model of AMI, possibly through decreasing serum proinflammatory cytokines and ET-1.

SOLDERING OF ALUMINUM BASE METALS

DOEpatents

Erickson, G.F.

1958-02-25

This patent deals with the soldering of aluminum to metals of different types, such as copper, brass, and iron. This is accomplished by heating the aluminum metal to be soldered to slightly above 30 deg C, rubbing a small amount of metallic gallium into the part of the surface to be soldered, whereby an aluminum--gallium alloy forms on the surface, and then heating the aluminum piece to the melting point of lead--tin soft solder, applying lead--tin soft solder to this alloyed surface, and combining the aluminum with the other metal to which it is to be soldered.

Study on the Tensile Creep Behavior of Carbon Nanotubes-Reinforced Sn-58Bi Solder Joints

NASA Astrophysics Data System (ADS)

Yang, Li; Liu, Haixiang; Zhang, Yaocheng

2018-01-01

The microstructure and tensile creep behavior of plain Sn-58Bi solder and carbon nanotubes (CNTs)-reinforced composite solder joints were investigated. The stress exponent n under different stresses and the creep activation energy Q c under different temperatures of solder joints were obtained by an empirical equation. The results reveal that the microstructure of the composite solder joint is refined and the tensile creep resistance is improved by CNTs. The improvement of creep behavior is due to the microstructural change of the composite solder joints, since the CNTs could provide more obstacles for dislocation pile-up, which enhances the values of the stress exponent and the creep activation energy. The steady-state tensile creep rates of plain solder and composite solder joints are increased with increasing temperature and applied stress. The tensile creep constitutive equations of plain solder and composite solder joints are written as \\dot{ɛ }_{s1} = 14.94( {σ /G} )^{3.7} \\exp ( { - 81444/RT} ) and \\dot{ɛ }_{s2} = 2.5( {σ /G} )^{4.38} \\exp ( { - 101582/RT} ) , respectively. The tensile creep mechanism of the solder joints is the effects of lattice diffusion determined by dislocation climbing.

Printability Optimization For Fine Pitch Solder Bonding

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kwon, Sang-Hyun; Lee, Chang-Woo; Yoo, Sehoon

2011-01-17

Effect of metal mask and pad design on solder printability was evaluated by DOE in this study. The process parameters were stencil thickness, squeegee angle, squeegee speed, mask separating speed, and pad angle of PCB. The main process parameters for printability were stencil thickness and squeegee angle. The response surface showed that maximum printability of 1005 chip was achieved at the stencil thickness of 0.12 mm while the maximum printability of 0603 and 0402 chip was obtained at the stencil thickness of 0.05 mm. The bonding strength of the MLCC chips was also directly related with the printability.

Control of microstructure in soldered, brazed, welded, plated, cast or vapor deposited manufactured components

DOEpatents

Ripley, Edward B.; Hallman, Russell L.

2015-11-10

Disclosed are methods and systems for controlling of the microstructures of a soldered, brazed, welded, plated, cast, or vapor deposited manufactured component. The systems typically use relatively weak magnetic fields of either constant or varying flux to affect material properties within a manufactured component, typically without modifying the alloy, or changing the chemical composition of materials or altering the time, temperature, or transformation parameters of a manufacturing process. Such systems and processes may be used with components consisting of only materials that are conventionally characterized as be uninfluenced by magnetic forces.

The Chemical Modeling of Electronic Materials and Interconnections

NASA Astrophysics Data System (ADS)

Kivilahti, J. K.

2002-12-01

Thermodynamic and kinetic modeling, together with careful experimental work, is of great help for developing new electronic materials such as lead-free solders, their compatible metallizations and diffusion-barrier layers, as well as joining and bonding processes for advanced electronics manufacturing. When combined, these modeling techniques lead to a rationalization of the trial-and-error methods employed in the electronics industry, limiting experimentation and, thus, reducing significantly time-to-market of new products. This modeling provides useful information on the stabilities of phases (microstructures), driving forces for chemical reactions, and growth rates of reaction products occurring in interconnections or thin-film structures during processing, testing, and in longterm use of electronic devices. This is especially important when manufacturing advanced lead-free electronics where solder joint volumes are decreasing while the number of dissimilar reactive materials is increasing markedly. Therefore, a new concept of local nominal composition was introduced and applied together with the relevant ternary and multicomponent phase diagrams to some solder/conductor systems.

Cytochrome c release in acute myocardial infarction predicts poor prognosis and myocardial reperfusion on contrast-enhanced magnetic resonance imaging.

PubMed

Liu, Zhen-Bing; Fu, Xiang-Hua; Wei, Geng; Gao, Jun-Ling

2014-01-01

Myocardial ischemia and reperfusion injury in ST-segment elevation myocardial infarction (STEMI) can trigger no-flow, resulting in myocardial necrosis and apoptosis, even a poor prognosis. Cytochrome c can induce an apoptotic process. The aim of our study was to assess the relationship between systemic cytochrome c levels and the occurrence of no-reflow in STEMI. One hundred and sixty patients with STEMI undergoing a primary percutaneous coronary intervention (PPCI) were randomly chosen. Patients were divided into two groups defined by the mean cytochrome c peak level after PPCI. No-reflow was assessed using three different methods after PPCI: myocardial blush grade, electrocardiographic ST-resolution, and microvascular obstruction (MO) assessed by cardiovascular magnetic resonance imaging. The primary clinical end points were major adverse cardiovascular events (defined as cardiac death, reinfarction, or new congestive heart failure). Clinical follow-up was carried out for 1 year. Patients with a cytochrome c level of at least the mean peak level had a greater creatine kinase-MB isoenzyme peak level (P=0.044), a lower left ventricular ejection fraction (P=0.029), a significantly higher occurrence of early MO (P=0.008), and a significantly larger extent of early MO (P=0.020). The cytochrome c peak level was elevated in patients with early MO (P=0.025), myocardial blush grade 0-1 (P=0.002), and ST-resolution less than 30% (P=0.003) after PPCI. A higher incidence of cardiac death at the 1-year follow-up was found in the patients with cytochrome c levels of at least the mean peak level (log rank, P=0.029). Cytochrome c levels above the mean peak level were related to no-reflow and mortality in patients with STEMI.

ESD Test Apparatus for Soldering Irons

NASA Technical Reports Server (NTRS)

Sancho, Jose; Esser, Robert

2013-01-01

ESDA (Electrostatic Discharge Association) ESD STM 13.1-2000 requires frequent testing of the voltage leakage from the tip of a soldering iron and the resistance from the tip of the soldering iron to the common point ground. Without this test apparatus, the process is time-consuming and requires several wires, alligator clips, or test probes, as well as additional equipment. Soldering iron tips must be tested for electrostatic discharge risks frequently, and this typically takes a lot of time in setup and testing. This device enables the operator to execute the full test in one minute or less. This innovation is a simple apparatus that plugs into a digital multimeter (DMM) and the Common Point Ground (CPG) reference. It enables the user to perform two of the electrostatic discharge tests required in ESD STM 13.1-2000. The device consists of a small black box with two prongs sticking out of one end, two inputs on the opposite end (one of the inputs is used to connect the reference CPG to the DMM), and a metal tab on one side. Inside the box are wires, several washers of various materials, and assembly hardware (nuts and screws/bolts). The device is a passive electronic component that is plugged into a DMM. The operator sets the DMM to read voltage. The operator places the heated tip of the soldering iron onto the metal tab with a small amount of solder to ensure a complete connection. The voltage is read and recorded. The operator switches the DMM to read resistance. The operator places the heated tip of the soldering iron onto the metal tab with a small amount of solder to ensure a complete connection. The resistance is recorded. If the recorded voltage and resistance are below a number stated in ESDA ESD STM 13.1-2000, the test is considered to pass. The device includes all the necessary wiring internal to its body so the operator does not need to do any independent wiring, except for grounding. It uses a stack of high-thermal-resistance washers to minimize the heat transfer from the soldering iron to the wiring used to measure the resistance and voltages. This minimizes thermal error. The device allows very rapid execution of a test that is performed frequently.

Histological Study of the Toxic Effects of Solder Fumes on Spermatogenesis in Rats

PubMed Central

Arab, Mohammad Reza; Heidari, Mohammad Hossein; Mashhadi, Rezvaneh; Mirzaei, Ramazan; Jahantigh, Mehdi

2011-01-01

Objective: Toxic fumes generated during the soldering process contain various contaminants released at sufficient rates to cause both short- and long-term health problems. Studies have shown that these fumes change the quality and quantity of semen fluid in exposed workers. The aim of the present study was to determine the potentially toxic effects of solder fumes on spermatogenesis in seminiferous tubules of rats as an experimental model, with conditioned media in an exposed chamber. Materials and Methods: A total number of 48 male Sprague Dawley adult rats were randomly divided into experimental (n=30) and control (n=18) groups. Based on exposure time, each group was further subdivided into two, four and six subgroups. Rats in the experimental groups were exposed to solder fumes in an exposure chamber for one hour/ day. The concentrations of fumes [formaldehyde, stanum (Sn) and lead (Pb)] were measured by a standard method via atomic absorption and spectrophotometry. According to a timetable, under deep anesthesia, the rats of both experimental and control subgroups were killed. After fixation of testes, specimens were weighed and routinely processed. Paraffin sections were stained by hematoxylin and eosin. Spermiogenesis index was calculated and data analyzed by Mann Whitney NPAR test. Results: Analysis of air samples in the exposure chamber showed the following fume concentrations: 0.193 mg/m3 for formaldehyde, 0.35 mg/m3 for Sn and 3 mg/m3 for Pb. Although there was no significant difference in testes weight between control and experimental subgroups, there was only a significant difference in spermiogenesis index between the six week experimental and control subgroups (p<0.02). Conclusion: The results of this study showed that solder fumes can change the spermiogenesis index in experimental groups in a time dependent manner. PMID:23671821

Effect of temperature and flux concentration on soldering of base metal.

PubMed

Lee, S Y; Lin, C T; Wang, M H; Tseng, H; Huang, H M; Dong, D R; Pan, L C; Shih, Y H

2000-12-01

The present study used the acoustic emission (AE) technique to evaluate interactions among soldering temperature, flux treatment, and the resultant ultimate tensile strength (UTS). Scanning electron microscopy (SEM) was used to examine fracture surfaces of the solder joints. Specimens were cast from removable partial denture alloy and then placed in a jig with a gap distance of 1.0 mm. A high-frequency soldering machine with an optical pyrometer was used for soldering at 1150 degrees C and 1200 degrees C, respectively. The flux concentrations were 67% and 75%. The soldered specimens were subjected to tensile test at a crosshead speed of 0.05 mm/min. During testing, acoustic emissions in the frequency range of 100--1200 kHz were collected, filtered, recorded, and processed by a sensing device. The results were analysed by ANOVA and Tukey LSD test. UTS at different temperatures showed no significant difference according to either mechanical or acoustic results. But in the 1200 degrees C group, the UTSs and AE counts showed significant differences (P<0.05) at both flux concentrations. SEM showed that the 1200C group had better dendritic crystal structure than did the 1150 degrees C group. In the 1200 degrees C group specimens with 67% flux had fewer flux inclusion bodies and dendritic crystals than did specimens with 75% flux. The 75% flux subgroup produced high-amplitude (60--70 dB) acoustic signals within the elastic deformation zone, while the 67% flux subgroup produced similar signals within the plastic deformation zone, either beyond the 0.2% yield point or before fracture.

Assembly processes comparison for a miniaturized laser used for the Exomars European Space Agency mission

NASA Astrophysics Data System (ADS)

Ribes-Pleguezuelo, Pol; Inza, Andoni Moral; Basset, Marta Gilaberte; Rodríguez, Pablo; Rodríguez, Gemma; Laudisio, Marco; Galan, Miguel; Hornaff, Marcel; Beckert, Erik; Eberhardt, Ramona; Tünnermann, Andreas

2016-11-01

A miniaturized diode-pumped solid-state laser (DPSSL) designed as part of the Raman laser spectrometer (RLS) instrument for the European Space Agency (ESA) Exomars mission 2020 is assembled and tested for the mission purpose and requirements. Two different processes were tried for the laser assembling: one based on adhesives, following traditional laser manufacturing processes; another based on a low-stress and organic-free soldering technique called solderjet bumping technology. The manufactured devices were tested for the processes validation by passing mechanical, thermal cycles, radiation, and optical functional tests. The comparison analysis showed a device improvement in terms of reliability of the optical performances from the soldered to the assembled by adhesive-based means.

Array automated assembly task, phase 2. Low cost silicon solar array project

NASA Technical Reports Server (NTRS)

Rhee, S. S.; Jones, G. T.; Allison, K. T.

1978-01-01

Several modifications instituted in the wafer surface preparation process served to significantly reduce the process cost to 1.55 cents per peak watt in 1975 cents. Performance verification tests of a laser scanning system showed a limited capability to detect hidden cracks or defects, but with potential equipment modifications this cost effective system could be rendered suitable for applications. Installation of electroless nickel plating system was completed along with an optimization of the wafer plating process. The solder coating and flux removal process verification test was completed. An optimum temperature range of 500-550 C was found to produce uniform solder coating with the restriction that a modified dipping procedure is utilized. Finally, the construction of the spray-on dopant equipment was completed.

Effects of soldering methods on tensile strength of a gold-palladium metal ceramic alloy.

PubMed

Ghadhanfari, Husain A; Khajah, Hasan M; Monaco, Edward A; Kim, Hyeongil

2014-10-01

The tensile strength obtained by conventional postceramic application soldering and laser postceramic welding may require more energy than microwave postceramic soldering, which could provide similar tensile strength values. The purpose of the study was to compare the tensile strength obtained by microwave postceramic soldering, conventional postceramic soldering, and laser postceramic welding. A gold-palladium metal ceramic alloy and gold-based solder were used in this study. Twenty-seven wax specimens were cast in gold-palladium noble metal and divided into 4 groups: laser welding with a specific postfiller noble metal, microwave soldering with a postceramic solder, conventional soldering with the same postceramic solder used in the microwave soldering group, and a nonsectioned control group. All the specimens were heat treated to simulate a normal porcelain sintering sequence. An Instron Universal Testing Machine was used to measure the tensile strength for the 4 groups. The means were analyzed statistically with 1-way ANOVA. The surface and fracture sites of the specimens were subjectively evaluated for fracture type and porosities by using a scanning electron microscope. The mean (standard deviation) ultimate tensile strength values were as follows: nonsectioned control 818 ±30 MPa, microwave 516 ±34 MPa, conventional 454 ±37 MPa, and laser weld 191 ±39 MPa. A 1-way ANOVA showed a significant difference in ultimate tensile strength among the groups (F3,23=334.5; P<.001). Follow-up multiple comparisons showed a significant difference among all the groups. Microwave soldering resulted in a higher tensile strength for gold and palladium noble metals than either conventional soldering or laser welding. Conventional soldering resulted in a higher tensile strength than laser welding. Under the experimental conditions described, either microwave or conventional postceramic soldering would appear to satisfy clinical requirements related to tensile strength. Copyright © 2014 Editorial Council for the Journal of Prosthetic Dentistry. Published by Elsevier Inc. All rights reserved.

Pick-and-place process for sensitivity improvement of the capacitive type CMOS MEMS 2-axis tilt sensor

NASA Astrophysics Data System (ADS)

Chang, Chun-I.; Tsai, Ming-Han; Liu, Yu-Chia; Sun, Chih-Ming; Fang, Weileun

2013-09-01

This study exploits the foundry available complimentary metal-oxide-semiconductor (CMOS) process and the packaging house available pick-and-place technology to implement a capacitive type micromachined 2-axis tilt sensor. The suspended micro mechanical structures such as the spring, stage and sensing electrodes are fabricated using the CMOS microelectromechanical systems (MEMS) processes. A bulk block is assembled onto the suspended stage by pick-and-place technology to increase the proof-mass of the tilt sensor. The low temperature UV-glue dispensing and curing processes are employed to bond the block onto the stage. Thus, the sensitivity of the CMOS MEMS capacitive type 2-axis tilt sensor is significantly improved. In application, this study successfully demonstrates the bonding of a bulk solder ball of 100 µm in diameter with a 2-axis tilt sensor fabricated using the standard TSMC 0.35 µm 2P4M CMOS process. Measurements show the sensitivities of the 2-axis tilt sensor are increased for 2.06-fold (x-axis) and 1.78-fold (y-axis) after adding the solder ball. Note that the sensitivity can be further improved by reducing the parasitic capacitance and the mismatch of sensing electrodes caused by the solder ball.

Soldering instrument safety improvements

DOEpatents

Kosslow, William J.; Giron, Ronald W.

1996-01-01

A safe soldering device includes a retractable heat shield which can be moved between a first position in which the solder tip of the device is exposed for soldering operation and a second position in which the solder tip is covered by the heat shield. Preferably, the heat shield is biased towards the second position and may be locked in the first position for ease of use. When the soldering device is equipped with a vacuum system, the heat shield may serve to guide the flow of gases and heat from the solder tip away from the work area. The heat shield is preferably made of non-heatsinking plastic.

Soldering In Space Investigation Video

NASA Technical Reports Server (NTRS)

2004-01-01

This video captures Mike Fincke melting solder during the first set of planned In-Space Soldering Investigation (ISSI) experiments onboard the International Space Station (ISS). In the video, Fincke touches the tip of the soldering iron to a wire wrapped with rosin-core solder. Review of the experiment video revealed melting kinetics, wetting characteristics, and equilibrium shape attainment of the solder charge. Samples returned to Earth were examined for porosity and flux distribution as well as microstructural development. ISSI's purpose was to find out how solder behaves in a weightless environment and promote our knowledge of fabrication and repair techniques that might be employed during extended space exploration missions.

Effects of Grain Orientation on Cu6Sn5 Growth Behavior in Cu6Sn5-Reinforced Composite Solder Joints During Electromigration

NASA Astrophysics Data System (ADS)

Han, Jing; Wang, Yan; Tan, Shihai; Guo, Fu

2018-02-01

Electromigration is a major reliability problem in composite solder joints. Due to the anisotropy of the β-Sn crystal structure, the Sn grain orientations present in the solder matrix dominate the principal failure mechanism in solder joints under electric current stressing. In this work, the Cu6Sn5 growth behavior in Cu6Sn5-reinforced composite solder joints with three different Sn grain orientations was investigated at current density of 104 A/cm2 at room temperature. Micron-sized Cu particles were added to Sn-3.5Ag solder at 2% volume fraction using an in situ method. After current stressing for 528 h, the polarity effect in the composite solder joint was greatest for an angle ( θ) between the c-axis and electron flow direction of 30°, resulting in higher growth rate of Cu6Sn5 in the solder matrix compared with composite solder joints with θ of 60° or 90°. There were no noticeable changes in the composite solder joint with θ of 90°. The growth behavior of Cu6Sn5, Cu atomic motion, and Cu diffusivity in the composite solder joints with different Sn grain orientations were analyzed in detail.

Recrystallization Behavior in Mixed Solder Joints of BGA Components during Thermal Shock

NASA Astrophysics Data System (ADS)

Tan, Shihai; Han, Jing; Guo, Fu

2018-03-01

Sn-37Pb and Sn-3.0Ag-0.5Cu solder pastes printed onto a board were attached to ball grid array (BGA) samples using Sn-3.0Ag-0.5Cu solder balls. Before thermal shock, the initial grain orientations on the cross-section were obtained by scanning electron microscopy equipped with an electron backscattered diffraction system. Three mixed solder joints (two from the corner and another from the middle of the BGA component) and three lead-free solder joints (at the same positions) were selected to investigate the recrystallization behavior under thermal shock (TS) cycling conditions. All of the mixed and lead-free solder joints were initially single crystal. The results showed that recrystallization occurred in both the mixed and lead-free solder joints after 200 TS. For the mixed solder joints, more recrystallization was observed and the location of samples had a significant influence on their recrystallization behavior, while location was not as important for the lead-free samples after 200 TS in this study. Both the mixed and lead-free solder joints at the corner of BGA components showed the poorest reliability. According to misorientation distribution maps and subgrain rotation behaviors, the reliability of mixed solder joints was much poorer than that of lead-free solder joints.

Direct-soldering 6061 aluminum alloys with ultrasonic coating.

PubMed

Ding, Min; Zhang, Pei-lei; Zhang, Zhen-yu; Yao, Shun

2010-02-01

In this study, the authors applied furnace soldering with ultrasonic coating method to solder 6061 aluminum alloy and investigated the effects of both coating time and soldering temperature on its properties. The following results were obtained: firstly, the solder region mainly composed of four kinds of microstructure zones: rich Sn zone, rich-Pb zone, Sn-Pb eutectic phase and rich Al zone. Meanwhile, the microanalysis identified a continuous reaction product at the alumina-solder interface as a rich-Pb zone. Therefore, the joint strength changed with soldering time and soldering temperature. Secondly, the tensile data had significantly greater variability, with values ranging from 13.99MPa to 24.74MPa. The highest value was obtained for the samples coated with Sn-Pb-Zn alloy for 45s. Fractures occurred along the solder-alumina interface for the 6061 aluminum alloy with its surface including hybrid tough fracture of dimple and tear ridge. The interface could initially strip at the rich Bi zone with the effect of shear stress.

Simple, low-cost fabrication of semi-circular channel using the surface tension of solder paste and its application to microfluidic valves.

PubMed

Yan, Sheng; Li, Yuxing; Zhu, Yuanqing; Liu, Minsu; Zhao, Qianbin; Yuan, Dan; Yun, Guolin; Zhang, Shiwu; Wen, Weijia; Tang, Shi-Yang; Li, Weihua

2018-06-01

This work presents a simple, low-cost method to fabricate semi-circular channels using solder paste, which can amalgamate the cooper surface to form a half-cylinder mold using the surface tension of Sn-Pd alloy (the main component in solder paste). This technique enables semi-circular channels to be manufactured with different dimensions. These semi-circular channels will then be integrated with a polymethylmethacrylate frame and machine screws to create miniaturized, portable microfluidic valves for sequential liquid delivery and particle synthesis. This approach avoids complicated fabrication processes and expensive facilities and thus has the potential to be a useful tool for lab-on-a-chip applications. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

A solder sealing method for paraffin-filled microcavities

NASA Astrophysics Data System (ADS)

Nguyen, Hugo; Bejhed, Johan; Köhler, Johan; Thornell, Greger

2006-11-01

Demonstrated and investigated here is a method to seal microfluidic systems by soldering. As a particularly difficult case of growing importance, the sealing of openings contaminated with paraffin wax was studied. Solder paste, screen printed on a metallized silicon substrate, was melted locally through application of 6.5-10 V to a 5 Ω copper film resistor for a few seconds and was found able to drive an intermediate layer of paraffin away and seal a 0.2 mm diameter circular via by wetting a surrounding copper pad. Although verified to be robust, the process did result in failing seals on excessive heating because of consumption of the pads. Correctly performed, the technique provided a seal at least withstanding a pressure of 8 bar for 8 h at 85 °C.

Laser assisted soldering: microdroplet accumulation with a microjet device.

PubMed

Chan, E K; Lu, Q; Bell, B; Motamedi, M; Frederickson, C; Brown, D T; Kovach, I S; Welch, A J

1998-01-01

We investigated the feasibility of a microjet to dispense protein solder for laser assisted soldering. Successive micro solder droplets were deposited on rat dermis and bovine intima specimens. Fixed laser exposure was synchronized with the jetting of each droplet. After photocoagulation, each specimen was cut into two halves at the center of solder coagulum. One half was fixed immediately, while the other half was soaked in phosphate-buffered saline for a designated hydration period before fixation (1 hour, 1, 2, and 7 days). After each hydration period, all tissue specimens were prepared for scanning electron microscopy (SEM). Stable solder coagulum was created by successive photocoagulation of microdroplets even after the soldered tissue exposed to 1 week of hydration. This preliminary study suggested that tissue soldering with successive microdroplets is feasible even with fixed laser parameters without active feedback control.

Effect of Electromigration on the Type of Drop Failure of Sn-3.0Ag-0.5Cu Solder Joints in PBGA Packages

NASA Astrophysics Data System (ADS)

Huang, M. L.; Zhao, N.

2015-10-01

Board-level drop tests of plastic ball grid array (PBGA) packages were performed in accordance with the Joint Electron Devices Engineering Council standard to investigate the effect of electromigration (EM) on the drop reliability of Sn-3.0Ag-0.5Cu solder joints with two substrate surface finishes, organic solderability preservative (OSP) and electroless nickel electroless palladium immersion gold (ENEPIG). In the as-soldered state, drop failures occurred at the substrate sides only, with cracks propagating within the interfacial intermetallic compound (IMC) layer for OSP solder joints and along the IMC/Ni-P interface for ENEPIG solder joints. The drop lifetime of OSP solder joints was approximately twice that of ENEPIG joints. EM had an important effect on crack formation and drop lifetime of the PBGA solder joints. ENEPIG solder joints performed better in drop reliability tests after EM, that is, the drop lifetime of ENEPIG joints decreased by 43% whereas that of OSP solder joints decreased by 91%, compared with the as-soldered cases. The more serious polarity effect, i.e., excessive growth of the interfacial IMC at the anode, was responsible for the sharper decrease in drop lifetime. The different types of drop failure of PBGA solder joints before and after EM, including the position of initiation and the propagation path of cracks, are discussed on the basis of the growth behavior of interfacial IMC.

Ultrasonic soldering of Cu alloy using Ni-foam/Sn composite interlayer.

PubMed

Xiao, Yong; Wang, Qiwei; Wang, Ling; Zeng, Xian; Li, Mingyu; Wang, Ziqi; Zhang, Xingyi; Zhu, Xiaomeng

2018-07-01

In this study, Cu alloy joints were fabricated with a Ni-foam reinforced Sn-based composite solder with the assistance of ultrasonic vibration. Effects of ultrasonic soldering time on the microstructure and mechanical properties of Cu/Ni-Sn/Cu joints were investigated. Results showed that exceptional metallurgic bonding could be acquired with the assistance of ultrasonic vibration using a self-developed Ni-foam/Sn composite solder. For joint soldered for 5 s, a (Cu,Ni) 6 Sn 5 intermetallic compound (IMC) layer was formed on the Cu substrate surface, Ni skeletons distributed randomly in the soldering seam and a serrated (Ni,Cu) 3 Sn 4 IMC layer was formed on the Ni skeleton surface. Increasing the soldering time to 20 s, the (Ni,Cu) 3 Sn 4 IMC layer grew significantly and exhibited a loose porous structure on the Ni skeleton surface. Further increase the soldering time to 30 s, Ni skeletons were largely dissolved in the Sn base solder, and micro-sized (Ni,Cu) 3 Sn 4 particles were formed and dispersed homogeneously in the soldering seam. The formation of (Ni,Cu) 3 Sn 4 particles was mainly ascribed to acoustic cavitations induced erosion and grain refining effects. The joint soldered for 30 s exhibited the highest shear strength of 64.9 ± 3.3 MPa, and the shearing failure mainly occurred at the soldering seam/Cu substrate interface. Copyright © 2018 Elsevier B.V. All rights reserved.

Distortion of three-unit implant frameworks during casting, soldering, and simulated porcelain firings.

PubMed

Zervas, P J; Papazoglou, E; Beck, F M; Carr, A B

1999-09-01

The aim of this study was to assess distortion inherent in casting, soldering, and simulated porcelain firings of screw-retained, implant-supported three-unit fixed partial dentures (FPDs). Ten wax patterns were fabricated on a die-stone cast containing two implants, 20 mm apart from center to center. Five specimens were cast in a high-palladium alloy, exposed to simulated porcelain firings, sectioned, and then soldered with low-fusing solder. Five specimens were cast, sectioned, soldered with high-fusing solder, and then exposed to simulated porcelain firings. For each specimen, two horizontal and six vertical distances between appropriately scribed reference points were measured with a traveling microscope. Comparisons were made among the various measurements taken after wax-pattern fabrication, casting, high- and low-fusing soldering, and each porcelain firing. Data were analyzed using a repeated-measures factorial ANOVA (alpha = 0.05). Significant difference was detected in the amount of horizontal distortion during casting (53 +/- 24 microns) and high-fusing soldering (-49 +/- 50 microns), as well as in the amount of horizontal distortion during high-fusing soldering (-49 +/- 50 microns) and low-fusing soldering (17 +/- 26 microns). However, no clinically significant difference was found in the amount of horizontal distortion during casting, low-fusing, and high-fusing soldering. The greatest amount of distortion during the simulated porcelain firings took place during the oxidizing cycle. Soldering did not improve the casting misfit of a three-unit implant-retained FPD model. Metal-ceramic implant frameworks should be oxidized before intraoral fit evaluation.

Ultrasonic-assisted soldering of fine-grained 7034 aluminum alloy using Sn-Zn solders below 300°C.

PubMed

Guo, Weibing; Luan, Tianmin; He, Jingshan; Yan, Jiuchun

2018-01-01

The fine-grained Al alloys prefer to be soldered at as low as temperature to keep their mechanical properties. Solders of Sn-4Zn, Sn-9Zn, and Sn-20Zn alloys were used to solder fine-grained 7034 Al alloy pieces by ultrasonic-assisted soldering below 300°C in air. The joint using Sn-4Zn solder had the highest tensile strength of 201MPa and the fractures occurred in both β-Sn and Sn-Zn eutectic phases. Such joint was much stronger than the 1060 Al joint using Sn-4Zn solder, and its strength had approached the strength of 7034 Al joint using Zn-5Al solder. The strength of the joints using Sn-9Zn and Sn-20Zn solders dropped to∼160MPa due to the appearance of weak interfaces between η-Zn and eutectic phases in the bond layers. All the joints using Sn-Zn solders had very strong interfacial bonding, and alumina interlayers were identified at all the interfaces. Al dissolved in the bond layer reacted with the O rapidly to form alumina interlayers at the interfaces under the ultrasonic action. Zn segregated at the interface and formed strong bonds with both the Al terminated surface of alumina and the bond layer, resulting in strong interfacial bonding between Sn-Zn solders and Al alloys. Copyright © 2017 Elsevier B.V. All rights reserved.

Properties of Sn3.8Ag0.7Cu Solder Alloy with Trace Rare Earth Element Y Additions

NASA Astrophysics Data System (ADS)

Hao, H.; Tian, J.; Shi, Y. W.; Lei, Y. P.; Xia, Z. D.

2007-07-01

In the current research, trace rare earth (RE) element Y was incorporated into a promising lead-free solder, Sn3.8Ag0.7Cu, in an effort to improve the comprehensive properties of Sn3.8Ag0.7Cu solder. The range of Y content in Sn3.8Ag0.7Cu solder alloys varied from 0 wt.% to 1.0 wt.%. As an illustration of the advantage of Y doping, the melting temperature, wettability, mechanical properties, and microstructures of Sn3.8Ag0.7CuY solder were studied. Trace Y additions had little influence on the melting behavior, but the solder showed better wettability and mechanical properties, as well as finer microstructures, than found in Y-free Sn3.8Ag0.7Cu solder. The Sn3.8Ag0.7Cu0.15Y solder alloy exhibited the best comprehensive properties compared to other solders with different Y content. Furthermore, interfacial and microstructural studies were conducted on Sn3.8Ag0.7Cu0.15Y solder alloys, and notable changes in microstructure were found compared to the Y-free alloy. The thickness of an intermetallic compound layer (IML) was decreased during soldering, and the growth of the IML was suppressed during aging. At the same time, the growth of intermetallic compounds (IMCs) inside the solder was reduced. In particular, some bigger IMC plates were replaced by fine, granular IMCs.

Cracking Problems and Mechanical Characteristics of PME and BME Ceramic Capacitors

NASA Technical Reports Server (NTRS)

Teverovsky, Alexander

2018-01-01

Most failures in MLCCs are caused by cracking that create shorts between opposite electrodes of the parts. A use of manual soldering makes this problem especially serious for space industry. Experience shows that different lots of ceramic capacitors might have different susceptibility to cracking under manual soldering conditions. This simulates a search of techniques that would allow revealing capacitors that are most robust to soldering-induced stresses. Currently, base metal electrode (BME) capacitors are introduced to high-reliability applications as a replacement of precious metal electrode (PME) parts. Understanding the difference in the susceptibility to cracking between PME and BME capacitors would facilitate this process. This presentation gives a review of mechanical characteristics measured in-situ on MLCCs that includes flexural strength, Vickers hardness, indentation fracture toughness, and the board flex testing and compare characteristics of BME and PME capacitors. A history case related to cracking in PME capacitors that caused flight system malfunctions and mechanisms of failure are considered. Possible qualification tests that would allow evaluation of the resistance of MLCCs to manual soldering are suggested and perspectives related to introduction of BME capacitors discussed.

Processing and Characterization of NiTi Shape Memory Alloy Particle Reinforced Sn-In Solders

DTIC Science & Technology

2006-12-01

solders generally operate at a high homologous temperature. Thermally induced grain growth, mechanical stress-induced grain growth and recrystallization ...the number of I/O connects available for flip chip as compared to the wirebond chip For interconnection and packaging, Pb-Sn and eutectic 63Sn...lower melting point is desired. The maximum use temperature for this alloy is around 120°C due to the fact that the eutectic reaction happened at

Video- Soldering Iron Inserted Through a Film of Water Onboard the International Space Station (ISS)

NASA Technical Reports Server (NTRS)

2003-01-01

Saturday Morning Science, the science of opportunity series of applied experiments and demonstrations, performed aboard the International Space Station (ISS) by Expedition 6 astronaut Dr. Don Pettit, revealed some remarkable findings. In this video, Dr. Pettit demonstrates the result of inserting a soldering iron into a thin film or sheet of water in space. Dr. Pettit makes comparative comments about the differences and similarities of boiling processes in space and on Earth.

Evaluation on the characteristics of tin-silver-bismuth solder

NASA Astrophysics Data System (ADS)

Xia, Z.; Shi, Y.; Chen, Z.

2002-02-01

Tin-silver-bismuth solder is characterized by its lower melting point, good wetting behavior, and good mechanical property for which it is expected to be a new lead-free solder to replace tin-lead solder. In this article, Sn-3.33Ag-4.83Bi solder was investigated concerning its physical, spreading, and mechanical properties under specific conditions. Cooling curves and DSC results showed that it was close to eutectic composition (m.p. 210° 212 °C). Coefficiency of thermal expansion (CTE) of this solder, between that of PCBs and copper substrates, was beneficial to alleviate the thermal mismatch of the substrates. It was also a good electrical and thermal conductor. Using a rosin-based, mildly activated (RMA) flux, a spreading test indicated that SnAgBi solder paste had good solderability. Meanwhile, the solder had high tensile strength and fracture energy. Its fracture mechanism was a mixture of ductile and brittle fracture morphology. The metallographic and EDAX analyses indicated that it was composed of a tin-based solid solution and some intermetallic compound (IMC) that could strengthen the substrate. However, these large needle-like IMCs would cut the substrate and this resulted in the decreasing of the toughness of the solder.

Die Soldering in Aluminium Die Casting

DOE Office of Scientific and Technical Information (OSTI.GOV)

Han, Q.; Kenik, E.A.; Viswanathan, S.

2000-03-15

Two types of tests, dipping tests and dip-coating tests were carried out on small steel cylinders using pure aluminum and 380 alloy to investigate the mechanism of die soldering during aluminum die casting. Optical and scanning electron microscopy were used to study the morphology and composition of the phases formed during soldering. A soldering mechanism is postulated based on experimental observations. A soldering critical temperature is postulated at which iron begins to react with aluminum to form an aluminum-rich liquid phase and solid intermetallic compounds. When the temperature at the die surface is higher than this critical temperature, the aluminum-richmore » phase is liquid and joins the die with the casting during the subsequent solidification. The paper discusses the mechanism of soldering for the case of pure aluminum and 380 alloy casting in a steel mold, the factors that promote soldering, and the strength of the bond formed when soldering occurs. conditions, an aluminum-rich soldering layer may also form over the intermetallic layer. Although a significant amount of research has been conducted on the nature of these intermetallics, little is known about the conditions under which soldering occurs.« less

Laser soldering technique for sutureless urethral surgery.

PubMed

Kirsch, A J; Canning, D A; Zderic, S A; Hensle, T W; Duckett, J W

1997-01-01

Investigators have attempted sutureless surgery to decrease operative time, lessen the inflammatory response, maintain luminal continuity, and increase the ease of performing technically difficult surgery. Only recently has laser-tissue welding (LTW) been used for urologic reconstruction in humans. Herein, we present our technique of laser soldering with the half-watt diode laser and wavelength matched albumin-based solder. Our methodology of LTW relies on bonding between the outer surface of the wound edges and the solder. The 808-nm diode wavelength does not penetrate deep tissue, and thus relies on indocyanine green dye to localize photon absorption. Since 1994, we have performed LTW, as an adjunct to suturing (N = 25) and as a primary means of tissue closure (N = 11). Preoperative diagnoses included hypospadias, urethral stricture, urethral diverticulum, and urethral fistulae. Follow-up ranged between 3 months and 3 years to identify complications of wound healing, stricture, and fistula formation. In the 37 patients undergoing urethral surgery, no strictures or diverticula have resulted. None of the patients have had wound infections or poor wound healing. Overall, five patients have developed fistulas between 2 weeks and 6 months postoperatively. The location of the hypospadiac meatus was scrotal or penoscrotal in four of these patients. Two fistulas developed following sutureless urethroplasty (reoperative) after traumatic catheterization for urinary retention (one case for inadvertent catheter removal). In our initial experience, the overall complication rate using laser soldering was 19% compared to 24% in an historical control group. Half of the complications occurred in a reoperative situation. More recently, the overall fistula rate was 14%; however, for primary cases, the current fistula rate is only 6%. LTW is safe and easy to perform. The application of protein solders (+/-chromophores) have permitted far greater tensile strengths to be achieved than laser alone. Temperature-control and chromophore-control have permitted safety and efficacy to be achieved. Solder application site and technique are equally important in the success of the LTW process. A randomized, prospective study comparing LTW to suturing is ongoing.

Temperature-controlled two-wavelength laser soldering of tissues.

PubMed

Gabay, Ilan; Abergel, Avraham; Vasilyev, Tamar; Rabi, Yaron; Fliss, Dan M; Katzir, Abraham

2011-11-01

Laser tissue soldering is a method for bonding of incisions in tissues. A biological solder is spread over the cut, laser radiation heats the solder and the underlying cut edges and the incision is bonded. This method offers many advantages over conventional techniques (e.g., sutures). Past researches have shown that laser soldering, using a single laser, does not provide sufficient strength for bonding of cuts in thick (>1 mm) tissues. This study introduces a novel method for laser soldering of thick tissues, under temperature control, using two lasers, emitting two different wavelengths. An experimental system was built, using two lasers: (i) a CO(2) laser, whose radiation heated the upper surface of the tissue and (ii) a GaAs laser that heated an albumin layer under the tissue. An infrared fiber-optic radiometer monitored the temperature of the tissue. All three devices were connected to a computer that controlled the process. A computer simulation was written to optimize the system parameters. The system was tested on tissue phantoms, to validate the simulation and ensure that both the upper and lower sides of the cut were heated, and that the temperature could be controlled on both sides. The system was then used ex vivo to bond longitudinal cuts of lengths ∼12 mm in the esophagi of large farm pigs. The theoretical simulations showed a good stabilization of the temperatures at the upper and lower tissue surfaces at the target values. Experiments on tissue phantom showed a good agreement with these simulations. Incisions in esophagi, removed from large farm pigs, were then successfully bonded. The mean burst pressure was ∼3.6 m of water. This study demonstrated the capability of soldering cuts in thick tissues, paving the way for new types of surgical applications. Copyright © 2010 Wiley Periodicals, Inc.

Solder for oxide layer-building metals and alloys

DOEpatents

Kronberg, James W.

1992-01-01

A low temperature solder and method for soldering an oxide layer-building metal such as aluminum, titanium, tantalum or stainless steel. The comosition comprises tin and zinc; germanium as a wetting agent; preferably small amounts of copper and antimony; and a grit, such as silicon carbide. The grit abrades any oxide layer formed on the surface of the metal as the germanium penetrates beneath and loosens the oxide layer to provide good metal-to-metal contact. The germanium comprises less than aproximatley 10% by weight of the solder composition so that it provides sufficient wetting action but does not result in a melting temperature above approximately 300.degree. C. The method comprises the steps rubbing the solder against the metal surface so the grit in the solder abrades the surface while heating the surface until the solder begins to melt and the germanium penetrates the oxide layer, then brushing aside any oxide layer loosened by the solder.

Solder for oxide layer-building metals and alloys

DOEpatents

Kronberg, J.W.

1992-09-15

A low temperature solder and method for soldering an oxide layer-building metal such as aluminum, titanium, tantalum or stainless steel is disclosed. The composition comprises tin and zinc; germanium as a wetting agent; preferably small amounts of copper and antimony; and a grit, such as silicon carbide. The grit abrades any oxide layer formed on the surface of the metal as the germanium penetrates beneath and loosens the oxide layer to provide good metal-to-metal contact. The germanium comprises less than approximately 10% by weight of the solder composition so that it provides sufficient wetting action but does not result in a melting temperature above approximately 300 C. The method comprises the steps rubbing the solder against the metal surface so the grit in the solder abrades the surface while heating the surface until the solder begins to melt and the germanium penetrates the oxide layer, then brushing aside any oxide layer loosened by the solder.

Anand constitutive model of lead-free solder joints in 3D IC device

NASA Astrophysics Data System (ADS)

Zhang, Liang; Liu, Zhi-quan; Ji, Yu-tong

2016-08-01

Anand constitutive relation of SnAgCu and SnAgCu-nano Al solders were studied under uniaxial tension, and the constitutive model was used in the finite element simulation to analyze the stress-strain response of lead-free solder joints in 3D IC devices. The results showed that the nine parameters of the Anand model can be determined from separated constitutive relations and experimental results. Based on Anand model, the finite element method was selected to calculate the stress-strain response of lead-free solder joints, it was found that in the 3D IC device the maximum stress-strain concentrated in the concern solder joints, the stress-strain of SnAgCu-nano Al solder joints was lower than that of SnAgCu solder joints, which represented that the addition of nano Al particles can enhance the reliability of lead-free solder joints in 3D IC devices.

Fixture facilitates soldering operations

NASA Technical Reports Server (NTRS)

White, C. M.

1968-01-01

Soldering fixture, designed for printed circuit cards, is a basic bench-mounted, self-contained integral unit combining all soldering needs into a compact, readily available work station. All tools, materials, and accessories are available to provide an ideal station to perform critical soldering.

Preparing Solar Cells for Soldering

NASA Technical Reports Server (NTRS)

Hagerty, J. J.

1983-01-01

Solder paste and contact ribbon dispensed in synchronism. Solder-paste dispenser operates on one cell at a time. Ribbon fed up ramps and into positioned while solder paste is applied. When ramps are moved out of way, ribbon lies down onto cell.

Laser-fiber coupling by means of a silicon micro-optical bench and a self-aligned soldering process

NASA Astrophysics Data System (ADS)

Schmidt, Jan P.; Cordes, A.; Mueller, Joerg; Burkhardt, Hans

1995-02-01

The alignment of laser diodes to monomode fibers has to meet extremely close tolerances for a low coupling loss. Typically < 0.5 micrometers in lateral and vertical direction and less than two degrees in angle deviation are allowed for a coupling loss below 2 dB. Presently such close tolerances can only be met by gluing or soldering both components on separate base plates and combining them via piezoactivated alignment monitoring the output of the circuit and then gluing them using UV-hardening epoxies. Such a procedure is not very economical and not useful for mass applications. This paper presents the principle and realization of a silicon micro-optical bench for laser-fiber-coupling, which avoids the above mentioned disadvantages. The micro-optical bench is realized using well controlled plasma etching processes to transfer the guiding patterns for the laser and the fiber into the silicon substrate, keeping geometry tolerances below +/- 0.5 micrometers in lateral and vertical direction. Mounting the laser diode by means of a self-aligned soldering process, an additional contribution to the precise alignment of the laser is further improved.

Space and Missile Systems Center Standard: Parts, Materials, and Processes Control Program for Launch Vehicles -SMC-S-011 (2012)

DTIC Science & Technology

2012-07-03

Specification for MIL-PRF-39008 Resistor Fixed, Composition ( Insulated ), Established Reliability, General Specification for MIL-S-45743 Soldering, Manual...2.1.5 Prohibited Relays 1. Plug-in types 2. Solder-sealed relays 2.1.6 Prohibited Resistors 1. All hollow glass or hollow ceramic core devices 2...lowest maximum temperature. This may be the core material, the insulation of the magnet, etc. 2/ Current rating for each winding shall be less than

Holographic optical element for laser soldering

NASA Astrophysics Data System (ADS)

Nakahara, Sumio; Hayashi, Tatsuya; Sudou, Noriyuki; Hisada, Shigeyoshi; Fujita, Takeyoshi

2002-02-01

Experimental studies on the characteristics of holographic lens were carried out, aiming at the simultaneous soldering of multi-spots in electronic assembly by the use of YAG laser. Holograms were recorded on the commercial available photographic plates, and converted into transparent phase type holographic lens by chemical processing. The dependencies of the diffraction efficiency on the recording conditions and two chemical treatment methods of silver halide sensitized gelatin and rehalogenating bleaching were examined in CW YAG laser system ((lambda) equals 1.06 micrometers ).

Annual Electronics Manufacturing Seminar Processings (18th) Held in Ridgecrest, California on 23-24 February 1994

DTIC Science & Technology

1994-02-01

rework, repair, and maintenance of electronic hardware as well as the initial manufacture. Chemically, HF1 189 is simply citric acid (derived from citrus...fruit) in water. Citric acid is highly soluble in water which allows simple water washing of hardware after soldering totally eliminating the need for...of citric acid in water. PCA’s soldered with either wave or hand techniques presented no cleaning problems if they were cleaned within one-half hour of

40 CFR 438.2 - General definitions.

Code of Federal Regulations, 2013 CFR

2013-07-01

... chemical conversion coating operations. (d) Metal-bearing operations means one or more of the following... descaling; shot tower—lead shot manufacturing; soldering; solder flux cleaning; solder fusing; solder...) Oily operations means one or more of the following: abrasive blasting; adhesive bonding; alkaline...

40 CFR 438.2 - General definitions.

Code of Federal Regulations, 2010 CFR

2010-07-01

... conversion coating operations. (d) Metal-bearing operations means one or more of the following: abrasive jet... descaling; shot tower—lead shot manufacturing; soldering; solder flux cleaning; solder fusing; solder...) Oily operations means one or more of the following: abrasive blasting; adhesive bonding; alkaline...

40 CFR 438.2 - General definitions.

Code of Federal Regulations, 2012 CFR

2012-07-01

... chemical conversion coating operations. (d) Metal-bearing operations means one or more of the following... descaling; shot tower—lead shot manufacturing; soldering; solder flux cleaning; solder fusing; solder...) Oily operations means one or more of the following: abrasive blasting; adhesive bonding; alkaline...

40 CFR 438.2 - General definitions.

Code of Federal Regulations, 2011 CFR

2011-07-01

... conversion coating operations. (d) Metal-bearing operations means one or more of the following: abrasive jet... descaling; shot tower—lead shot manufacturing; soldering; solder flux cleaning; solder fusing; solder...) Oily operations means one or more of the following: abrasive blasting; adhesive bonding; alkaline...

40 CFR 438.2 - General definitions.

Code of Federal Regulations, 2014 CFR

2014-07-01

... chemical conversion coating operations. (d) Metal-bearing operations means one or more of the following... descaling; shot tower—lead shot manufacturing; soldering; solder flux cleaning; solder fusing; solder...) Oily operations means one or more of the following: abrasive blasting; adhesive bonding; alkaline...

An evaluation of the lap-shear test for Sn-rich solder/Cu couples: Experiments and simulation

NASA Astrophysics Data System (ADS)

Chawla, N.; Shen, Y.-L.; Deng, X.; Ege, E. S.

2004-12-01

The lap-shear technique is commonly used to evaluate the shear, creep, and thermal fatigue behavior of solder joints. We have conducted a parametric experimental and modeling study, on the effect of testing and geometrical parameters on solder/copper joint response in lap-shear. It was shown that the farfield applied strain is quite different from the actual solder strain (measured optically). Subtraction of the deformation of the Cu substrate provides a reasonable approximation of the solder strain in the elastic regime, but not in the plastic regime. Solder joint thickness has a profound effect on joint response. The solder response moves progressively closer to “true” shear response with increasing joint thickness. Numerical modeling using finite-element analyses were performed to rationalize the experimental findings. The same lap-shear configuration was used in the simulation. The input response for solder was based on the experimental tensile test result on bulk specimens. The calculated shear response, using both the commonly adopted far-field measure and the actual shear strain in solder, was found to be consistent with the trends observed in the lap-shear experiments. The geometric features were further explored to provide physical insight into the problem. Deformation of the substrate was found to greatly influence the shear behavior of the solder.

Effects of CuZnAl Particles on Properties and Microstructure of Sn-58Bi Solder

PubMed Central

Yang, Fan; Zhang, Liang; Liu, Zhi-quan; Zhong, Su Juan; Ma, Jia; Bao, Li

2017-01-01

With the purpose of improving the properties of the Sn-58Bi lead-free solder, micro-CuZnAl particles ranging from 0 to 0.4 wt % were added into the low temperature eutectic Sn-58Bi lead-free solder. After the experimental testing of micro-CuZnAl particles on the properties and microstructure of the Sn-58Bi solders, it was found that the wettability of the Sn-58Bi solders was obviously improved with addition of CuZnAl particles. When the addition of CuZnAl particles was 0.2 wt %, the wettability of the Sn-58Bi solder performed best. At the same time, excessive addition of CuZnAl particles led to poor wettability. However, the results showed that CuZnAl particles changed the melting point of the Sn-58Bi solder slightly. The microstructure of the Sn-58Bi solder was refined by adding CuZnAl particles. When the content of CuZnAl addition was between 0.1 and 0.2 wt %, the refinement was great. In addition, the interfacial IMC layer between new composite solder and Cu substrate was thinner than that between the Sn-58Bi solder and Cu substrate. PMID:28772917

[Absence of blood circulation following toe-hand transplantation in a 7-year-old girl with monodactyle form of symbrachydactyly].

PubMed

Coenen, L; Brouwers, J

1990-03-01

In a toe transplantation in a child with symbrachydactyly the authors were faced with a no-reflow phenomenon. The medication they used in prophylaxis was not an absolute guarantee to prevent this problem. Success also depends on some general measures, as a stable blood pressure, a constant blood volume, normal body temperature, short operation time, and an early revision in case of a no-reflow phenomenon. Some questions about the appearance of spasm still remain: are they provoked by pain, stress, medication as anaesthetics, or is a congenital structural vessel problem responsible?

Early stages of soldering reactions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lord, R.A.; Umantsev, A.

2005-09-15

An experiment on the early stages of intermetallic compound layer growth during soldering and its theoretical analysis were conducted with the intent to study the controlling factors of the process. An experimental technique based on fast dipping and pulling of a copper coupon in liquid solder followed by optical microscopy allowed the authors to study the temporal behavior of the sample on a single micrograph. The technique should be of value for different areas of metallurgy because many experiments on crystallization may be described as the growth of a layer of intermediate phase. Comparison of the experimental results with themore » theoretical calculations allowed one to identify the kinetics of dissolution as the rate-controlling mechanism on the early stages and measure the kinetic coefficient of dissolution. A popular model of intermetallic compound layer structure coarsening is discussed.« less

Nanoshell assisted laser soldering of vascular tissue.

PubMed

Schöni, Daniel S; Bogni, Serge; Bregy, Amadé; Wirth, Amina; Raabe, Andreas; Vajtai, Istvan; Pieles, Uwe; Reinert, Michael; Frenz, Martin

2011-12-01

Laser tissue soldering (LTS) is a promising technique for tissue fusion but is limited by the lack of reproducibility particularly when the amount of indocyanine green (ICG) applied as energy absorber cannot be controlled during the soldering procedure. Nanotechnology enables the control over the quantitative binding of the ICG. The aim of this study was to establish a highly reproducible and strong tissue fusion using ICG packed nanoshells. By including the chromophore in the soldering scaffold, dilution of the energy absorber during the soldering procedure is prevented. The feasibility of this novel nanoshell soldering technique was studied by assessing the local heating of the area and tensile strength of the resulting fused tissue. Nanoshells with a diameter of 250-270 nm were loaded with ICG and included in a porous polycaprolactone (PCL) scaffold doped with albumin solder. The nanoshell scaffold was used in a flexible, semi-dry formulation suitable for surgical use. Heat development, tensile strength as well as tissue damage were assessed. Rabbit aortic arteries were successfully soldered using an ICG packed nanoshell scaffold. Tensile strengths of these nanoshell soldered anastomoses were found to be 734 ± 327 mN (median = 640 mN). Thermal damage was restricted to the adventitia at the irradiated area. In addition, absorber dilution was prevented during the soldering procedure resulting in significantly lower variance in maximum temperature (P = 0.03) compared to the classical liquid ICG soldering technique. Using nanoshells, controlled amounts of chromophore could successfully be bound into the polymer scaffold. Diode laser soldering of vascular tissue using ICG-nanoshell scaffolds leads to strong and reproducible tissue fusion. With optimally chosen settings of irradiation time, nanoshells coating and scaffold properties, our improved LTS procedure demonstrates the potential for a clinically applicable anastomosis technique. Copyright © 2011 Wiley Periodicals, Inc.

Effect of Sn-Ag-Cu on the Improvement of Electromigration Behavior in Sn-58Bi Solder Joint

NASA Astrophysics Data System (ADS)

Wang, Fengjiang; Zhou, Lili; Zhang, Zhijie; Wang, Jiheng; Wang, Xiaojing; Wu, Mingfang

2017-10-01

Reliability issues caused by the formation of a Bi-rich layer at the anode interface usually occurs in the Sn-58Bi eutectic solder joint during electromigration (EM). To improve the EM performance of a Sn-58Bi solder joint, Sn-3.0Ag-0.5Cu solder was introduced into it to produce SnBi-SnAgCu structural or compositional composite joints, and their EM behaviors were investigated with the current density of 1.0 × 104 A/cm2 for different stressing times. The structure of the compositional composite solder joint was obtained by the occurrence of partial or full mixing between Sn-Bi and Sn-Ag-Cu solder with a suitable soldering temperature. In the structural composite joint, melted Sn-Bi was partially mixed with Sn-Ag-Cu solder to produce a Cu/Sn-Bi/Sn-Ag-Cu/Sn-Bi/Cu structure. In the compositional composite joint, full melting and mixing between these two solders occurred to produce a Cu/Sn-Ag-Cu-Bi/Cu structure, in which the solder matrix was a homogeneous structure including Sn, Bi phases, Cu6Sn5 and Ag3Sn IMCs. After current stressing, the EM performance of Sn-Bi solder was obviously improved with the structural or the compositional composite joint. In Sn-58Bi joints, a thick Bi-rich layer was easily produced at the anode interface, and obviously increased with stressing time. However, after current stressing on the structural composite joints, the existence of s Sn-3.0Ag-0.5Cu interlayer between the two Sn-58Bi solders effectively acted as a diffusion barrier and significantly slowed the formation of the Bi-rich layer at the anode side and the IMC thicknesses at the interfaces.

Influence of nanoparticle addition on the formation and growth of intermetallic compounds (IMCs) in Cu/Sn–Ag–Cu/Cu solder joint during different thermal conditions

PubMed Central

Ting Tan, Ai; Wen Tan, Ai; Yusof, Farazila

2015-01-01

Nanocomposite lead-free solders are gaining prominence as replacements for conventional lead-free solders such as Sn–Ag–Cu solder in the electronic packaging industry. They are fabricated by adding nanoparticles such as metallic and ceramic particles into conventional lead-free solder. It is reported that the addition of such nanoparticles could strengthen the solder matrix, refine the intermetallic compounds (IMCs) formed and suppress the growth of IMCs when the joint is subjected to different thermal conditions such as thermal aging and thermal cycling. In this paper, we first review the fundamental studies on the formation and growth of IMCs in lead-free solder joints. Subsequently, we discuss the effect of the addition of nanoparticles on IMC formation and their growth under several thermal conditions. Finally, an outlook on the future growth of research in the fabrication of nanocomposite solder is provided. PMID:27877786

Wetting reaction of Sn-Ag based solder systems on Cu substrates plated with Au and/or Pd layer

NASA Astrophysics Data System (ADS)

Liu, C. Y.; Li, Jian; Vandentop, G. J.; Choi, W. J.; Tu, K. N.

2001-05-01

The wetting behavior of SnAg based Pb-free solders on Cu and Cu substrates plated with Au, Pd, and Au/Pd thin films have been studied. The wetting angle and kinetics of interfacial reaction were measured. The Au-plated substrates exhibit better wetting than the Pd-plated substrates. In the case of SnAg on Pd-plated Cu, SEM observation revealed that the solder cap was surrounded by an innerring of Cu-Sn compound and an outer ring of Pd-Sn compound. This implies that the molten SnAg solder had removed the Pd and wetted the Cu directly in the equilibrium state. The effects of pre-doping Cu in the SnAg solder on wetting behavior were also investigated. We found that wettability decreases with increasing Cu content in the solder. We also observed that the SnAgCu solders have a lower Cu consumption rate than the SnAg solder.

Imaging and Analysis of Void-defects in Solder Joints Formed in Reduced Gravity using High-Resolution Computed Tomography

NASA Technical Reports Server (NTRS)

Easton, John W.; Struk, Peter M.; Rotella, Anthony

2008-01-01

As a part of efforts to develop an electronics repair capability for long duration space missions, techniques and materials for soldering components on a circuit board in reduced gravity must be developed. This paper presents results from testing solder joint formation in low gravity on a NASA Reduced Gravity Research Aircraft. The results presented include joints formed using eutectic tin-lead solder and one of the following fluxes: (1) a no-clean flux core, (2) a rosin flux core, and (3) a solid solder wire with external liquid no-clean flux. The solder joints are analyzed with a computed tomography (CT) technique which imaged the interior of the entire solder joint. This replaced an earlier technique that required the solder joint to be destructively ground down revealing a single plane which was subsequently analyzed. The CT analysis technique is described and results presented with implications for future testing as well as implications for the overall electronics repair effort discussed.

Lead-free solder

DOEpatents

Anderson, Iver E.; Terpstra, Robert L.

2001-05-15

A Sn--Ag--Cu eutectic alloy is modified with one or more low level and low cost alloy additions to enhance high temperature microstructural stability and thermal-mechanical fatigue strength without decreasing solderability. Purposeful fourth or fifth element additions in the collective amount not exceeding about 1 weight % (wt. %) are added to Sn--Ag--Cu eutectic solder alloy based on the ternary eutectic Sn--4.7%Ag--1.7%Cu (wt. %) and are selected from the group consisting essentially of Ni, Fe, and like-acting elements as modifiers of the intermetallic interface between the solder and substrate to improve high temperature solder joint microstructural stability and solder joint thermal-mechanical fatigue strength.

An Accelerated Method for Testing Soldering Tendency of Core Pins

DOE Office of Scientific and Technical Information (OSTI.GOV)

Han, Qingyou; Xu, Hanbing; Ried, Paul

2010-01-01

An accelerated method for testing die soldering has been developed. High intensity ultrasonic vibrations has been used to simulate the die casting conditions such as high pressure and high impingement speed of molten metal on the pin. Soldering tendency of steels and coated pins has been examined. The results indicate that in the low carbon steel/Al system, the onset of soldering is 60 times faster with ultrasonic vibration than that without ultrasonic vibration. In the H13/A380 system, the onset of soldering reaction is accelerated to 30-60 times. Coating significantly reduces the soldering tendency of the core pins.

Laser-activated protein solder for peripheral nerve repair

NASA Astrophysics Data System (ADS)

Trickett, Rodney I.; Lauto, Antonio; Dawes, Judith M.; Owen, Earl R.

1995-05-01

A 100 micrometers core optical fiber-coupled 75 mW diode laser operating at a wavelength of 800 nm has been used in conjunction with a protein solder to stripe weld severed rat tibial nerves, reducing the long operating time required for microsurgical nerve repair. Welding is produced by selective laser denaturation of the albumin based solder which contains the dye indocyanine green. Operating time for laser soldering was 10 +/- 5 min. (n equals 20) compared to 23 +/- 9 min. (n equals 10) for microsuturing. The laser solder technique resulted in patent welds with a tensile strength of 15 +/- 5 g, while microsutured nerves had a tensile strength of 40 +/- 10 g. Histopathology of the laser soldered nerves, conducted immediately after surgery, displayed solder adhesion to the outer membrane with minimal damage to the inner axons of the nerves. An in vivo study is under way comparing laser solder repaired tibial nerves to conventional microsuture repair. At the time of submission 15 laser soldered nerves and 7 sutured nerves were characterized at 3 months and showed successful regeneration with compound muscle action potentials of 27 +/- 8 mV and 29 +/- 8 mW respectively. A faster, less damaging and long lasting laser based anastomotic technique is presented.

Effect of the Angle Between Sn Grain c-Axis and Electron Flow Direction on Cu-Reinforced Composite Solder Joints Under Current Stressing

NASA Astrophysics Data System (ADS)

Wang, Yan; Han, Jing; Wang, Yishu; Ma, Limin; Guo, Fu

2018-01-01

With a body-centered tetragonal crystal structure, Sn grains were demonstrated to have highly anisotropic behaviors in various properties. The electromigration behavior of lead-free solder was impacted by the grain orientations. In this paper, the angle between the c-axis and the electron flow direction in composite solder joints (angle θ) was proven to be an important factor during electromigration. The effects of angle θ on the electromigration of composite solder joints were investigated in this paper. Cu particle-reinforced Sn3.5Ag solder joints were stressed under a current density of 104 A/cm2 at room temperature. After 336 h current stressing time, different electromigration phenomena occurred at the two sides of the grain boundary in the composite solder joint which contained two Sn grains with different angle θ. The Sn grains with the larger angle θ had a smaller growth rate of Cu6Sn5. In addition, a composite solder joint with a single Sn grain was set as the contrast and its angle θ was smaller than that of the composite solder joint with two Sn grains. The growth rate of Cu6Sn5 in the composite solder joint with a single grain was faster than that of the composite solder joint with two Sn grains.

Evaluation of advanced microelectronic fluxless solder-bump contacts for hybrid microcircuits

NASA Technical Reports Server (NTRS)

Mandal, R. P.

1976-01-01

Technology for interconnecting monolithic integrated circuit chips with other components is investigated. The advantages and disadvantages of the current flip-chip approach as compared to other interconnection methods are outlined. A fluxless solder-bump contact technology is evaluated. Multiple solder-bump contacts were formed on silicon integrated circuit chips. The solder-bumps, comprised of a rigid nickel under layer and a compliant solder overlayer, were electroformed onto gold device pads with the aid of thick dry film photomasks. Different solder alloys and the use of conductive epoxy for bonding were explored. Fluxless solder-bump bond quality and reliability were evaluated by measuring the effects of centrifuge, thermal cycling, and high temperature storage on bond visual characteristics, bond electrical continuity, and bond shear tests. The applicability and suitability of this technology for hybrid microelectronic packaging is discussed.

30 CFR 77.1916 - Welding, cutting, and soldering; fire protection.

Code of Federal Regulations, 2010 CFR

2010-07-01

... 30 Mineral Resources 1 2010-07-01 2010-07-01 false Welding, cutting, and soldering; fire... OF UNDERGROUND COAL MINES Slope and Shaft Sinking § 77.1916 Welding, cutting, and soldering; fire protection. (a) One portable fire extinguisher shall be provided where welding, cutting, or soldering with...

Heat Lamps Solder Solar Array Quickly

NASA Technical Reports Server (NTRS)

Coyle, P. J.; Crouthamel, M. S.

1982-01-01

Interconnection tabs in a nine-solar-cell array have been soldered simultaneously with radiant heat. Cells and tabs are held in position for soldering by sandwiching them between compliant silicone-rubber vacuum platen and transparent polyimide sealing membrane. Heat lamps warm cells, producing smooth, flat solder joints of high quality.

Testing of printed circuit board solder joints by optical correlation

NASA Technical Reports Server (NTRS)

Espy, P. N.

1975-01-01

An optical correlation technique for the nondestructive evaluation of printed circuit board solder joints was evaluated. Reliable indications of induced stress levels in solder joint lead wires are achievable. Definite relations between the inherent strength of a solder joint, with its associated ability to survive stress, are demonstrable.

30 CFR 77.1916 - Welding, cutting, and soldering; fire protection.

Code of Federal Regulations, 2011 CFR

2011-07-01

... 30 Mineral Resources 1 2011-07-01 2011-07-01 false Welding, cutting, and soldering; fire... OF UNDERGROUND COAL MINES Slope and Shaft Sinking § 77.1916 Welding, cutting, and soldering; fire protection. (a) One portable fire extinguisher shall be provided where welding, cutting, or soldering with...

30 CFR 77.1916 - Welding, cutting, and soldering; fire protection.

Code of Federal Regulations, 2012 CFR

2012-07-01

... 30 Mineral Resources 1 2012-07-01 2012-07-01 false Welding, cutting, and soldering; fire... OF UNDERGROUND COAL MINES Slope and Shaft Sinking § 77.1916 Welding, cutting, and soldering; fire protection. (a) One portable fire extinguisher shall be provided where welding, cutting, or soldering with...

30 CFR 77.1916 - Welding, cutting, and soldering; fire protection.

Code of Federal Regulations, 2014 CFR

2014-07-01

... 30 Mineral Resources 1 2014-07-01 2014-07-01 false Welding, cutting, and soldering; fire... OF UNDERGROUND COAL MINES Slope and Shaft Sinking § 77.1916 Welding, cutting, and soldering; fire protection. (a) One portable fire extinguisher shall be provided where welding, cutting, or soldering with...

30 CFR 77.1916 - Welding, cutting, and soldering; fire protection.

Code of Federal Regulations, 2013 CFR

2013-07-01

... 30 Mineral Resources 1 2013-07-01 2013-07-01 false Welding, cutting, and soldering; fire... OF UNDERGROUND COAL MINES Slope and Shaft Sinking § 77.1916 Welding, cutting, and soldering; fire protection. (a) One portable fire extinguisher shall be provided where welding, cutting, or soldering with...

Reactions in Electrodeposited Cu/Sn and Cu/Ni/Sn Nanoscale Multilayers for Interconnects

PubMed Central

Chia, Pay Ying; Haseeb, A. S. M. A.; Mannan, Samjid Hassan

2016-01-01

Miniaturization of electronic devices has led to the development of 3D IC packages which require ultra-small-scale interconnections. Such small interconnects can be completely converted into Cu-Sn based intermetallic compounds (IMCs) after reflow. In an effort to improve IMC based interconnects, an attempt is made to add Ni to Cu-Sn-based IMCs. Multilayer interconnects consisting of stacks of Cu/Sn/Cu/Sn/Cu or Cu/Ni/Sn/Ni/Sn/Cu/Ni/Sn/Ni/Cu with Ni = 35 nm, 70 nm, and 150 nm were electrodeposited sequentially using copper pyrophosphate, tin methanesulfonic, and nickel Watts baths, respectively. These multilayer interconnects were investigated under room temperature aging conditions and for solid-liquid reactions, where the samples were subjected to 250 °C reflow for 60 s and also 300 °C for 3600 s. The progress of the reaction in the multilayers was monitored by using X-ray Diffraction, Scanning Electron Microscope, and Energy dispersive X-ray Spectroscopy. FIB-milled samples were also prepared for investigation under room temperature aging conditions. Results show that by inserting a 70 nanometres thick Ni layer between copper and tin, premature reaction between Cu and Sn at room temperature can be avoided. During short reflow, the addition of Ni suppresses formation of Cu3Sn IMC. With increasing Ni thickness, Cu consumption is decreased and Ni starts acting as a barrier layer. On the other hand, during long reflow, two types of IMC were found in the Cu/Ni/Sn samples which are the (Cu,Ni)6Sn5 and (Cu,Ni)3Sn, respectively. Details of the reaction sequence and mechanisms are discussed. PMID:28773552

New Coating Technique of Ceramic Implants with Different Glass Solder Matrices for Improved Osseointegration-Mechanical Investigations.

PubMed

Mick, Enrico; Markhoff, Jana; Mitrovic, Aurica; Jonitz, Anika; Bader, Rainer

2013-09-11

Ceramics are a very popular material in dental implant technology due to their tribological properties, their biocompatibility and their esthetic appearance. However, their natural surface structure lacks the ability of proper osseointegration, which constitutes a crucial process for the stability and, thus, the functionality of a bone implant. We investigated the application of a glass solder matrix in three configurations-consisting mainly of SiO₂, Al₂O₃, K₂O and Na₂O to TZP-A ceramic specimens. The corresponding adhesive strength and surface roughness of the coatings on ceramic specimens have been analyzed. Thereby, high adhesive strength (70.3 ± 7.9 MPa) was found for the three different coatings. The obtained roughness (R z ) amounted to 18.24 ± 2.48 µm in average, with significant differences between the glass solder configurations. Furthermore, one configuration was also tested after additional etching which did not lead to significant increase of surface roughness (19.37 ± 1.04 µm) or adhesive strength (57.2 ± 5.8 MPa). In conclusion, coating with glass solder matrix seems to be a promising surface modification technique that may enable direct insertion of ceramic implants in dental and orthopaedic surgery.

Control Al/Mg intermetallic compound formation during ultrasonic-assisted soldering Mg to Al.

PubMed

Xu, Zhiwu; Li, Zhengwei; Li, Jiaqi; Ma, Zhipeng; Yan, Jiuchun

2018-09-01

To prevent the formation of Al/Mg intermetallic compounds (IMCs) of Al 3 Mg 2 and Al 12 Mg 17 , dissimilar Al/Mg were ultrasonic-assisted soldered using Sn-based filler metals. A new IMC of Mg 2 Sn formed in the soldered joints during this process and it was prone to crack at large thickness. The thickness of Mg 2 Sn was reduced to 22 μm at 285 °C when using Sn-3Cu as the filler metal. Cracks were still observed inside the blocky Mg 2 Sn. The thickness of Mg 2 Sn was significantly reduced when using Sn-9Zn as the filler metal. A 17 μm Mg 2 Sn layer without crack was obtained at a temperature of 200 °C, ultrasonic power of Mode I, and ultrasonic time of 2 s. The shear strengths of the joints using Sn-9Zn was much higher than those using Sn-3Cu because of the thinner Mg 2 Sn layer in the former joints. Sn whiskers were prevented by using Sn-9Zn. A cavitation model during ultrasonic assisted soldering was proposed. Copyright © 2018 Elsevier B.V. All rights reserved.

Capacitor Test, Evaluation. and Modeling Within NASA Electronic Parts and Packaging (NEPP) Program. "Why Ceramic Capacitors Fracture During Manual Soldering and How to Avoid Failures"

NASA Technical Reports Server (NTRS)

Teverovsky, Alexander

2011-01-01

Presentation discusses: (1) Why Multi-Layer Ceramic Capacitors(MLCCs) crack during manual soldering? Workmanship and parts issues. (2) Do existing qualification requirements assure crack-free soldering? MIL-spec Thermal Shock (TS) testing. MIL-spec Resistance to Soldering Heat (RSH) test. (3) What test can assure reliable soldering? Mechanical characteristics of ceramics. Comparison of three TS techniques: LND, TSD, and IWT. (4) Simulation of TS conditions.

Solderability of pre-tinned Cu sheet

NASA Astrophysics Data System (ADS)

Sunwoo, A. J.; Morris, J. W.; Lucey, G. K.

1992-05-01

The reliability and integrity of pre-tinned copper-clad printed circuit (PC) boards are serious concerns in the manufacture of electronic devices. The factors that influence the wetting during soldering of Cu are discussed. The results suggest that pre-tinning with a Pb-rich solder, such as 95Pb-5Sn, is preferred to pre-tinning with eutectic solder, since the latter can develop exposed intermetallics during aging that wet poorly. The results also confirm that the use of flux leads to carbon contamination in the solder.

Aspects of the structural evolution of lead-free solder joints

NASA Astrophysics Data System (ADS)

Zribi, A.; Kinyanjui, R.; Borgesen, P.; Zavalij, L.; Cotts, E. J.

2002-06-01

Studies of the formation of intermetallic compounds at some lead-free solder/metallization interfaces are briefly reviewed in this article. SnAgCu/Ni and SnAgCu/Cu interfaces are examined in particular. It has been found that (Cu,Ni)6Sn5 forms at SnAgCu/Ni interfaces until copper is depleted from the solder matrix. This article also contrasts the formation of (Au,Ni)Sn4 and related compounds in PbSn/Ni solder joints and lead-free solder joints.

Laparoscopic laser soldering for repair of ureteropelvic junction obstruction in the porcine model.

PubMed

Shumalinsky, Dmitry; Lobik, Leonid; Cytron, Shmuel; Halpern, Marisa; Vasilyev, Tamar; Ravid, Avi; Katzir, Abraham

2004-03-01

Laparoscopic pyeloplasty is used for the repair of ureteropelvic junction (UPJ) obstruction. Our objective was to introduce laser soldering to this procedure. We developed a system based on a CO2 laser, an infrared detector, and two infrared transmitting optical fibers to obtain temperature-controlled laser soldering of cuts in tissues. The system was used for laparoscopic soldering of incisions in the kidneys of pigs. We carried out laparoscopic pyeloplasty successfully in a porcine model using fiberoptic laser soldering. Laparoscopic laser soldering was found to be faster than suturing. It was easier to use and provided watertight bonding. This technique will be useful in pyeloplasty as well as other laparoscopic surgical procedures.

Size effects in tin-based lead-free solder joints: Kinetics of bond formation and mechanical characteristics

NASA Astrophysics Data System (ADS)

Abdelhadi, Ousama Mohamed Omer

Continuous miniaturization of microelectronic interconnects demands smaller joints with comparable microstructural and structural sizes. As the size of joints become smaller, the volume of intermetallics (IMCs) becomes comparable with the joint size. As a result, the kinetics of bond formation changes and the types and thicknesses of IMC phases that form within the constrained region of the bond varies. This dissertation focuses on investigating combination effects of process parameters and size on kinetics of bond formation, resulting microstructure and the mechanical properties of joints that are formed under structurally constrained conditions. An experiment is designed where several process parameters such as time of bonding, temperature, and pressure, and bond thickness as structural chracteristic, are varied at multiple levels. The experiment is then implemented on the process. Scanning electron microscope (SEM) is then utilized to determine the bond thickness, IMC phases and their thicknesses, and morphology of the bonds. Electron backscatter diffraction (EBSD) is used to determine the grain size in different regions, including the bulk solder, and different IMC phases. Physics-based analytical models have been developed for growth kinetics of IMC compounds and are verified using the experimental results. Nanoindentation is used to determine the mechanical behavior of IMC phases in joints in different scales. Four-point bending notched multilayer specimen and four-point bending technique were used to determine fracture toughness of the bonds containing IMCs. Analytical modeling of peeling and shear stresses and fracture toughness in tri-layer four-point bend specimen containing intermetallic layer was developed and was verified and validated using finite element simulation and experimental results. The experiment is used in conjunction with the model to calculate and verify the fracture toughness of Cu6Sn5 IMC materials. As expected two different IMC phases, η-phase (Cu6Sn 5) and epsilon-phase (Cu3Sn), were found in almost all the cases regardless of the process parameters and size levels. The physics-based analytical model was successfully able to capture the governing mechanisms of IMC growth: chemical reaction controlled and diffusion-controlled. Examination of microstructures of solder joints of different sizes revealed the size of the solder joint has no effect on the type of IMCs formed during the process. Joint size, however, affected the thickness of IMC layers significantly. IMC layers formed in the solder joints of smaller sizes were found to be thicker than those in the solder joints of larger sizes. The growth rate constants and activation energies of Cu3Sn IMC layer were also reported and related to joint thickness. In an effort to optimize the EBSD imaging in the multi-layer configuration, an improved specimen preparation technique and optimum software parameters were determined. Nanoindentation results show that size effects play a major role on the mechanical properties of micro-scale solder joints. Smaller joints show higher Young's modulus, hardness, and yield strength and lower work hardening exponents comparing to thicker joints. To obtain the stress concentration factors in a multilayer specimen with IMC layer as bonding material, a four-point bending notched configuration was used. The analytical solutions developed for peeling and shear stresses in notched structure were used to evaluate the stresses at IMC interface layers. Results were in good agreement with the finite-element simulation. The values of interfacial stresses were utilized in obtaining fracture toughness of the IMC material. (Abstract shortened by UMI.)

Corrosive microenvironments at lead solder surfaces arising from galvanic corrosion with copper pipe.

PubMed

Nguyen, Caroline K; Stone, Kendall R; Dudi, Abhijeet; Edwards, Marc A

2010-09-15

As stagnant water contacts copper pipe and lead solder (simulated soldered joints), a corrosion cell is formed between the metals in solder (Pb, Sn) and the copper. If the resulting galvanic current exceeds about 2 μA/cm(2), a highly corrosive microenvironment can form at the solder surface, with pH < 2.5 and chloride concentrations at least 11 times higher than bulk water levels. Waters with relatively high chloride tend to sustain high galvanic currents, preventing passivation of the solder surface, and contributing to lead contamination of potable water supplies. The total mass of lead corroded was consistent with predictions based on the galvanic current, and lead leaching to water was correlated with galvanic current. If the concentration of sulfate in the water increased relative to chloride, galvanic currents and associated lead contamination could be greatly reduced, and solder surfaces were readily passivated.

Concentrated autologous plasma protein: a biochemically neutral solder for tissue welding.

PubMed

Stewart, R B; Bleustein, C B; Petratos, P B; Chin, K C; Poppas, D P; Kung, R T

2001-01-01

Xenographic or allographic serum protein solders used for laser welding may have immunologic and/or pathogenic complications. The objective of these studies was to develop a safe, autologous solder. Five methods of preparing concentrated autologous plasma protein solder (CAPPS) were evaluated. Next, the CAPPS was evaluated via (1) thermal denaturation studies using differential scanning calorimetry, (2) tissue welding studies to characterize both acute and healing properties. The optimal concentration method to produce CAPPS rapidly was a dialysis method using chemical (osmotic) forces. The CAPPS showed similar denaturation profiles to serum albumin (SA) solders. Acutely, CAPPS provided comparable breaking strengths to SA solders. At 7 days, there was no significant difference in breaking strength or histology between 50% human SA solder and CAPPS (using a porcine skin model). These studies demonstrate that the CAPPS system provides acceptable acute and chronic properties for laser welding. Copyright 2001 Wiley-Liss, Inc.

Modeling the Rate-Dependent Durability of Reduced-Ag SAC Interconnects for Area Array Packages Under Torsion Loads

NASA Astrophysics Data System (ADS)

Srinivas, Vikram; Menon, Sandeep; Osterman, Michael; Pecht, Michael G.

2013-08-01

Solder durability models frequently focus on the applied strain range; however, the rate of applied loading, or strain rate, is also important. In this study, an approach to incorporate strain rate dependency into durability estimation for solder interconnects is examined. Failure data were collected for SAC105 solder ball grid arrays assembled with SAC305 solder that were subjected to displacement-controlled torsion loads. Strain-rate-dependent (Johnson-Cook model) and strain-rate-independent elastic-plastic properties were used to model the solders in finite-element simulation. Test data were then used to extract damage model constants for the reduced-Ag SAC solder. A generalized Coffin-Manson damage model was used to estimate the durability. The mechanical fatigue durability curve for reduced-silver SAC solder was generated and compared with durability curves for SAC305 and Sn-Pb from the literature.

Laser Inspection Or Soldered Connections

NASA Astrophysics Data System (ADS)

Alper, Richard I.; Traub, Alan C.

1986-07-01

A sensitive infrared detection system monitors the slight warming and cooling of a solder joint on a PWB in response to a focused laser beam pulse lasting for 30 milliseconds. Heating and cooling rates depend on the surface finish of the solder and also upon its interr.1 features. Joints which are alike show similar heating rates; defects behave differently and are flagged as showing abnormal thermal signatures Defects include surface voids, cold solder, insufficient or missing solder, residual solder flux, contamination and large subsurface voids. Solder bridges can usually be found by targeting at suspected bridge locations. Feed-through joints at DIPs and lap joints at flat-pack ICs are readily inspected by this method. By use of computer-controlled tiltable optics, access is had to the "harder to see" joints such as at leadless chip carriers and other surface mounts. Inspection rates can be up to 10 joints per second.

Composition of low-strength solder joints in solar-concentrator-cell arrays

NASA Astrophysics Data System (ADS)

Chamberlain, M. B.; Nordstrom, T. V.

Bond strengths of Cu strips soldered to the backside metallization of solar concentrator cells were found to be unacceptably low. To determine whether contaminants in the cell metallization caused these low strengths, unsoldered cells and soldered cells were characterized by scanning Auger microscopy. The backside metallization consisted of a 5 micrometers Ag conductor layer, a 150 nm Pd diffusion barrier and a 150 nm Ti adhesion layer next to an Al ohmic contact layer on the Si cell. The analysis showed that the Ti layer are partially oxidized during soldering, that Pb from the Pb-5 wt % Sn - 2.5 wt % Ag solder segregated during soldering to the Pd-oxidized Ti interface, and that low strength fractures occurred in this Pb layer at the Pd-oxidized Ti interface. The problem was solved by changing the ambient gas used during soldering from N2 to forming gas (80% N2 + 20% H2).

30 CFR 77.1112 - Welding, cutting, or soldering with arc or flame; safeguards.

Code of Federal Regulations, 2010 CFR

2010-07-01

... 30 Mineral Resources 1 2010-07-01 2010-07-01 false Welding, cutting, or soldering with arc or... WORK AREAS OF UNDERGROUND COAL MINES Fire Protection § 77.1112 Welding, cutting, or soldering with arc or flame; safeguards. (a) When welding, cutting, or soldering with arc or flame near combustible...

30 CFR 77.1112 - Welding, cutting, or soldering with arc or flame; safeguards.

Code of Federal Regulations, 2011 CFR

2011-07-01

... 30 Mineral Resources 1 2011-07-01 2011-07-01 false Welding, cutting, or soldering with arc or... WORK AREAS OF UNDERGROUND COAL MINES Fire Protection § 77.1112 Welding, cutting, or soldering with arc or flame; safeguards. (a) When welding, cutting, or soldering with arc or flame near combustible...

30 CFR 77.1112 - Welding, cutting, or soldering with arc or flame; safeguards.

Code of Federal Regulations, 2014 CFR

2014-07-01

... 30 Mineral Resources 1 2014-07-01 2014-07-01 false Welding, cutting, or soldering with arc or... WORK AREAS OF UNDERGROUND COAL MINES Fire Protection § 77.1112 Welding, cutting, or soldering with arc or flame; safeguards. (a) When welding, cutting, or soldering with arc or flame near combustible...

30 CFR 77.1112 - Welding, cutting, or soldering with arc or flame; safeguards.

Code of Federal Regulations, 2012 CFR

2012-07-01

... 30 Mineral Resources 1 2012-07-01 2012-07-01 false Welding, cutting, or soldering with arc or... WORK AREAS OF UNDERGROUND COAL MINES Fire Protection § 77.1112 Welding, cutting, or soldering with arc or flame; safeguards. (a) When welding, cutting, or soldering with arc or flame near combustible...

30 CFR 77.1112 - Welding, cutting, or soldering with arc or flame; safeguards.

Code of Federal Regulations, 2013 CFR

2013-07-01

... 30 Mineral Resources 1 2013-07-01 2013-07-01 false Welding, cutting, or soldering with arc or... WORK AREAS OF UNDERGROUND COAL MINES Fire Protection § 77.1112 Welding, cutting, or soldering with arc or flame; safeguards. (a) When welding, cutting, or soldering with arc or flame near combustible...

Method for optical and mechanically coupling optical fibers

DOEpatents

Toeppen, J.S.

1996-10-01

A method and apparatus are disclosed for splicing optical fibers. A fluorescing solder glass frit having a melting point lower than the melting point of first and second optical fibers is prepared. The solder glass frit is then attached to the end of the first optical fiber and/or the end of the second optical fiber. The ends of the optical fibers are aligned and placed in close proximity to each other. The solder glass frit is then heated to a temperature which is lower than the melting temperature of the first and second optical fibers, but which is high enough to melt the solder glass frit. A force is applied to the first and second optical fibers pushing the ends of the fibers towards each other. As the solder glass flit becomes molten, the layer of molten solder glass is compressed into a thin layer between the first and second optical fibers. The thin compressed layer of molten solder glass is allowed to cool such that the first and second optical fibers are bonded to each other by the hardened layer of solder glass. 6 figs.

Method for optical and mechanically coupling optical fibers

DOEpatents

Toeppen, John S.

1996-01-01

A method and apparatus for splicing optical fibers. A fluorescing solder glass frit having a melting point lower than the melting point of first and second optical fibers is prepared. The solder glass frit is then attached to the end of the first optical fiber and/or the end of the second optical fiber. The ends of the optical fibers are aligned and placed in close proximity to each other. The solder glass frit is then heated to a temperature which is lower than the melting temperature of the first and second optical fibers, but which is high enough to melt the solder glass frit. A force is applied to the first and second optical fibers pushing the ends of the fibers towards each other. As the solder glass flit becomes molten, the layer of molten solder glass is compressed into a thin layer between the first and second optical fibers. The thin compressed layer of molten solder glass is allowed to cool such that the first and second optical fibers are bonded to each other by the hardened layer of solder glass.

Temperature-controlled laser-soldering system and its clinical application for bonding skin incisions

NASA Astrophysics Data System (ADS)

Simhon, David; Gabay, Ilan; Shpolyansky, Gregory; Vasilyev, Tamar; Nur, Israel; Meidler, Roberto; Hatoum, Ossama Abu; Katzir, Abraham; Hashmonai, Moshe; Kopelman, Doron

2015-12-01

Laser tissue soldering is a method of repairing incisions. It involves the application of a biological solder to the approximated edges of the incision and heating it with a laser beam. A pilot clinical study was carried out on 10 patients who underwent laparoscopic cholecystectomy. Of the four abdominal incisions in each patient, two were sutured and two were laser soldered. Cicatrization, esthetical appearance, degree of pain, and pruritus in the incisions were examined on postoperative days 1, 7, and 30. The soldered wounds were watertight and healed well, with no discharge from these wounds or infection. The total closure time was equal in both methods, but the net soldering time was much shorter than suturing. There was no difference between the two types of wound closure with respect to the pain and pruritus on a follow-up of one month. Esthetically, the soldered incisions were estimated as good as the sutured ones. The present study confirmed that temperature-controlled laser soldering of human skin incisions is clinically feasible, and the results obtained were at least equivalent to those of standard suturing.

Temperature-controlled laser-soldering system and its clinical application for bonding skin incisions.

PubMed

Simhon, David; Gabay, Ilan; Shpolyansky, Gregory; Vasilyev, Tamar; Nur, Israel; Meidler, Roberto; Hatoum, Ossama Abu; Katzir, Abraham; Hashmonai, Moshe; Kopelman, Doron

2015-01-01

Laser tissue soldering is a method of repairing incisions. It involves the application of a biological solder to the approximated edges of the incision and heating it with a laser beam. A pilot clinical study was carried out on 10 patients who underwent laparoscopic cholecystectomy. Of the four abdominal incisions in each patient, two were sutured and two were laser soldered. Cicatrization, esthetical appearance, degree of pain, and pruritus in the incisions were examined on postoperative days 1, 7, and 30. The soldered wounds were watertight and healed well, with no discharge from these wounds or infection. The total closure time was equal in both methods, but the net soldering time was much shorter than suturing. There was no difference between the two types of wound closure with respect to the pain and pruritus on a follow-up of one month. Esthetically, the soldered incisions were estimated as good as the sutured ones. The present study confirmed that temperature-controlled laser soldering of human skin incisions is clinically feasible, and the results obtained were at least equivalent to those of standard suturing.

New multicomponent solder alloys of low melting pointfor low-cost commercial electronic assembly

NASA Astrophysics Data System (ADS)

Al-Ganainy, G. S.; Sakr, M. S.

2003-09-01

The requirements of the telecommunications, automobile, electronics and aircraft industries for non-toxic solders with melting points close to that of near-eutectic Pb-Sn alloys has led to the development of new Sn-Zn-In solder alloys. Differential thermal analysis (DTA) shows melting points of 198, 195, 190 and 185 +/- 2 °C for the alloys Sn-9Zn, Sn-9Zn-2In, Sn-9Zn-4In and Sn-9Zn-6In, respectively. An equation that fits the data relating the melting point to the In content in the solders is derived. The X-ray diffraction patterns are analyzed to determine the phases that exist in each solder. The stress-strain curves are studied in the temperature range from 90 to 130 °C for all the solders except for those that contain 4 wt% of In, where the temperature range continues to 150 °C. The work-hardening parameters, y (the yield stress), f (the fracture stress), and the parabolic work-hardening coefficient X, increase with increasing indium content in the solders at all working temperatures. They decrease with increasing working temperature for each solder, and show two relaxation stages only for the Sn-9Zn-4In solder around a temperature of 120 °C. (

Tissue soldering with biodegradable polymer films: in-vitro investigation of hydration effects on weld strength

NASA Astrophysics Data System (ADS)

Sorg, Brian S.; Welch, Ashley J.

2001-05-01

Previous work demonstrated increased breaking strengths of tissue repaired with liquid albumin solder reinforced with a biodegradable polymer film compared to unreinforced control specimens. It was hypothesized that the breaking strength increase was due to reinforcement of the liquid solder cohesive strength. Immersion in a moist environment can decrease the adhesion of solder to tissue and negate any strength benefits gained from reinforcement. The purpose of this study was to determine if hydrated specimens repaired with reinforced solder would still be stronger than unreinforced controls. A 50%(w/v) bovine serum albumin solder with 0.5 mg/mL Indocyanine Green dye was used to repair an incision in bovine aorta. The solder was coagulated with 806-nm diode laser light. A poly(DL-lactic- co-glycolic acid) film was used to reinforce the solder (the controls had no reinforcement). The repaired tissues were immersed in phosphate buffered saline for time periods of 1 and 2 days. The breaking strengths of all of the hydrated specimens decreased compared to the acute breaking strengths. However, the reinforced specimens still had larger breaking strengths than the unreinforced controls. These results indicate that reinforcement of a liquid albumin solder may have the potential to improve the breaking strength in a clinical setting.

Effect of Strain Rate on Joint Strength and Failure Mode of Lead-Free Solder Joints

NASA Astrophysics Data System (ADS)

Lin, Jian; Lei, Yongping; Fu, Hanguang; Guo, Fu

2018-03-01

In surface mount technology, the Sn-3.0Ag-0.5Cu solder joint has a shorter impact lifetime than a traditional lead-tin solder joint. In order to improve the impact property of SnAgCu lead-free solder joints and identify the effect of silver content on tensile strength and impact property, impact experiments were conducted at various strain rates on three selected SnAgCu based solder joints. It was found that joint failure mainly occurred in the solder material with large plastic deformation under low strain rate, while joint failure occurred at the brittle intermetallic compound layer without any plastic deformation at a high strain rate. Joint strength increased with the silver content in SnAgCu alloys in static tensile tests, while the impact property of the solder joint decreased with increasing silver content. When the strain rate was low, plastic deformation occurred with failure and the tensile strength of the Sn-3.0Ag-0.5Cu solder joint was higher than that of Sn-0.3Ag-0.7Cu; when the strain rate was high, joint failure mainly occurred at the brittle interface layer and the Sn-0.3Ag-0.7Cu solder joint had a better impact resistance with a thinner intermetallic compound layer.

Nanocomposite SAC Solders: The Effect of Adding Ni and Ni-Sn Nanoparticles on Morphology and Mechanical Properties of Sn-3.0Ag-0.5Cu Solders

NASA Astrophysics Data System (ADS)

Yakymovych, A.; Švec, P.; Orovcik, L.; Bajana, O.; Ipser, H.

2018-01-01

This study investigates the effect of minor additions of Ni, Ni3Sn or Ni3Sn2 nanoparticles on the microstructure and mechanical properties of Cu/solder/Cu joints. The nanocomposite Sn-3.0Ag-0.5Cu (SAC305) solders with 0.5, 1.0 and 2.0 wt.% metallic nanoparticles were prepared through a paste mixing method. The employed Ni and Ni-Sn nanoparticles were produced via a chemical reduction method. The microstructure of as-solidified Cu/solder/Cu joints was studied by x-ray diffraction and scanning electron microscopy. The results showed that additions of Ni and Ni-Sn nanoparticles to the SAC305 solder paste lead initially to a decrease in the average thickness of the intermetallic compound layer in the interface between solder and substrate, while further additions up to 2.0 wt.% did not induce any significant changes. In addition, shear strength and microhardness tests were performed to investigate the relationship between microstructure and mechanical properties of the investigated solder joints. The results indicated an increase in both of these properties which was most significant for the solder joints using SAC305 with 0.5 wt.% Ni or Ni-Sn nanoparticles.

Laser Scanner For Automatic Inspection Of Printed Wiring Boards

NASA Astrophysics Data System (ADS)

Geise, Philip; George, Eugene; Freese, Fritz; Brown, Robert; Ruwe, Victor

1980-11-01

An, Instrument is described which inspects unpopulated, populated (components onserted and leads clinched), and soldered printed wiring boards for correct hole location, component presence, correct lead clinch direction and solder bridges. The instrument consists of a low power heliumneon laser, an x-y moving iron galvanometer scanner and several folding mirros. A unique shadow signature is detected by silicon photodiodes located at the optium geometry to allow rapid and reliable detection of components with correctly clinched leads. A reflective glint screen is utilized to inspect for a solder bridges. The detected signal are processed and evaluated by a minocomputer which also controls the scan inspection rate of at least 25 components or 50 components holes per second. The return of investment on this instrument for high volume production of printed wirind boards is less than one yea and only slightly longer for medium run military application.

Effect of soldering techniques and gap distance on tensile strength of soldered Ni-Cr alloy joint.

PubMed

Lee, Sang-Yeob; Lee, Jong-Hyuk

2010-12-01

The present study was intended to evaluate the effect of soldering techniques with infrared ray and gas torch under different gap distances (0.3 mm and 0.5 mm) on the tensile strength and surface porosity formation in Ni-Cr base metal alloy. Thirty five dumbbell shaped Ni-Cr alloy specimens were prepared and assigned to 5 groups according to the soldering method and the gap distance. For the soldering methods, gas torch (G group) and infrared ray (IR group) were compared and each group was subdivided by corresponding gap distance (0.3 mm: G3 and IR3, 0.5 mm: G5, IR5). Specimens of the experimental groups were sectioned in the middle with a diamond disk and embedded in solder blocks according to the predetermined distance. As a control group, 7 specimens were prepared without sectioning or soldering. After the soldering procedure, a tensile strength test was performed using universal testing machine at a crosshead speed 1 mm/min. The proportions of porosity on the fractured surface were calculated on the images acquired through the scanning electronic microscope. Every specimen of G3, G5, IR3 and IR5 was fractured on the solder joint area. However, there was no significant difference between the test groups (P > .05). There was a negative correlation between porosity formation and tensile strength in all the specimens in the test groups (P < .05). There was no significant difference in ultimate tensile strength of joints and porosity formations between the gas-oxygen torch soldering and infrared ray soldering technique or between the gap distance of 0.3 mm and 0.5 mm.

Effect of soldering techniques and gap distance on tensile strength of soldered Ni-Cr alloy joint

PubMed Central

Lee, Sang-Yeob

2010-01-01

PURPOSE The present study was intended to evaluate the effect of soldering techniques with infrared ray and gas torch under different gap distances (0.3 mm and 0.5 mm) on the tensile strength and surface porosity formation in Ni-Cr base metal alloy. MATERIALS AND METHODS Thirty five dumbbell shaped Ni-Cr alloy specimens were prepared and assigned to 5 groups according to the soldering method and the gap distance. For the soldering methods, gas torch (G group) and infrared ray (IR group) were compared and each group was subdivided by corresponding gap distance (0.3 mm: G3 and IR3, 0.5 mm: G5, IR5). Specimens of the experimental groups were sectioned in the middle with a diamond disk and embedded in solder blocks according to the predetermined distance. As a control group, 7 specimens were prepared without sectioning or soldering. After the soldering procedure, a tensile strength test was performed using universal testing machine at a crosshead speed 1 mm/min. The proportions of porosity on the fractured surface were calculated on the images acquired through the scanning electronic microscope. RESULTS Every specimen of G3, G5, IR3 and IR5 was fractured on the solder joint area. However, there was no significant difference between the test groups (P > .05). There was a negative correlation between porosity formation and tensile strength in all the specimens in the test groups (P < .05). CONCLUSION There was no significant difference in ultimate tensile strength of joints and porosity formations between the gas-oxygen torch soldering and infrared ray soldering technique or between the gap distance of 0.3 mm and 0.5 mm. PMID:21264189

Albumin-genipin solder for laser tissue repair.

PubMed

Lauto, A; Foster, L J R; Ferris, L; Avolio, A; Zwaneveld, N; Poole-Warren, L A

2004-01-01

Laser tissue soldering (LTS) is an alternative technique to suturing for tissue repair that avoids foreign body reaction and provides immediate sealing of the wound. One of the major drawbacks of LTS, however, is the weak tensile strength of the solder welds when compared to sutures. In this study, a crosslinking agent of low cytotoxicity was investigated for its ability to enhance the bond strength of albumin solders with sheep intestine. Solder strips were welded onto rectangular sections of sheep small intestine using a diode laser. The laser delivered in continuous mode a power of 170 +/- 10 mW at lambda = 808 nm, through a multimode optical fiber (core size = 200 microm) to achieve a dose of 10.8 +/- 0.5 J/mg. The solder thickness and surface area were kept constant throughout the experiment (thickness = 0.15 +/- 0.01 mm, area = 12 +/- 1.2 mm2). The solder was composed of 62% bovine serum albumin (BSA), 0.38% genipin, 0.25% indocyanin green dye (IG), and water. Tissue welding was also performed with a BSA solder without genipin, as a control group. The repaired tissue was tested for tensile strength by a calibrated tensiometer. Murine fibroblasts were also cultured in extracted media from heat-denatured genipin solder to assess cell growth inhibition in a 48 hours period. The tensile strength of the genipin solder was doubled that of the BSA solder (0.21 +/- 0.04 N and 0.11 +/- 0.04 N, respectively; P = 10(-15) unpaired t-test, N = 30). Media extracted from crosslinked genipin solder showed negligible toxicity to fibroblast cells under the culture conditions examined here. Addition of a chemical crosslinking agent, such as genipin, significantly increased the tensile strength of adhesive-tissue bonds. A proposed mechanism for this enhanced bond strength is the synergistic action of mechanical adhesion with chemical crosslinking by genipin.

Mechanistic Prediction of the Effect of Microstructural Coarsening on Creep Response of SnAgCu Solder Joints

NASA Astrophysics Data System (ADS)

Mukherjee, S.; Chauhan, P.; Osterman, M.; Dasgupta, A.; Pecht, M.

2016-07-01

Mechanistic microstructural models have been developed to capture the effect of isothermal aging on time dependent viscoplastic response of Sn3.0Ag0.5Cu (SAC305) solders. SnAgCu (SAC) solders undergo continuous microstructural coarsening during both storage and service because of their high homologous temperature. The microstructures of these low melting point alloys continuously evolve during service. This results in evolution of creep properties of the joint over time, thereby influencing the long term reliability of microelectronic packages. It is well documented that isothermal aging degrades the creep resistance of SAC solder. SAC305 alloy is aged for (24-1000) h at (25-100)°C (~0.6-0.8 × T melt). Cross-sectioning and image processing techniques were used to periodically quantify the effect of isothermal aging on phase coarsening and evolution. The parameters monitored during isothermal aging include size, area fraction, and inter-particle spacing of nanoscale Ag3Sn intermetallic compounds (IMCs) and the volume fraction of micronscale Cu6Sn5 IMCs, as well as the area fraction of pure tin dendrites. Effects of microstructural evolution on secondary creep constitutive response of SAC305 solder joints were then modeled using a mechanistic multiscale creep model. The mechanistic phenomena modeled include: (1) dispersion strengthening by coarsened nanoscale Ag3Sn IMCs in the eutectic phase; and (2) load sharing between pro-eutectic Sn dendrites and the surrounding coarsened eutectic Sn-Ag phase and microscale Cu6Sn5 IMCs. The coarse-grained polycrystalline Sn microstructure in SAC305 solder was not captured in the above model because isothermal aging does not cause any significant change in the initial grain size and orientation of SAC305 solder joints. The above mechanistic model can successfully capture the drop in creep resistance due to the influence of isothermal aging on SAC305 single crystals. Contribution of grain boundary sliding to the creep strain of coarse grained joints has not been modeled in this study.

Hi-rel lead-free printed wiring assemblies

NASA Technical Reports Server (NTRS)

Mehta, A. C.; Bonner, J. K.; Castillo, L. del

2002-01-01

The use of lead in electronics has come under increasing scrutiny. Given the trends in both Japan and Europe, it is highly likely that the U.S. will be driven by commercial interests to phase out of lead in electronics usage. This paper presents data collected on a recent NASA project to focus on finding suitable alternatives to eutectic tin-lead solders and solder pastes. The first phase of this project dealt with determining the most feasible candidates to replace tin-lead and to determine suitable processing operations in assemblies printed wiring boards.

Finite Element Analysis of Laser Engineered Net Shape (LENS™) Tungsten Clad Squeeze Pins

NASA Astrophysics Data System (ADS)

Sakhuja, Amit; Brevick, Jerald R.

2004-06-01

In the aluminum high-pressure die-casting and indirect squeeze casting processes, local "squeeze" pins are often used to minimize internal solidification shrinkage in heavy casting sections. Squeeze pins frequently fail in service due to molten aluminum adhering to the H13 tool steel pins ("soldering"). A wide variety of coating materials and methods have been developed to minimize soldering on H13. However, these coatings are typically very thin, and experience has shown their performance on squeeze pins is highly variable. The LENS™ process was employed in this research to deposit a relatively thick tungsten cladding on squeeze pins. An advantage of this process was that the process parameters could be precisely controlled in order to produce a satisfactory cladding. Two fixtures were designed and constructed to enable the end and outer diameter (OD) of the squeeze pins to be clad. Analyses were performed on the clad pins to evaluate the microstructure and chemical composition of the tungsten cladding and the cladding-H13 substrate interface. A thermo-mechanical finite element analysis (FEA) was performed to assess the stress distribution as a function of cladding thickness on the pins during a typical casting thermal cycle. FEA results were validated via a physical test, where the clad squeeze pins were immersed into molten aluminum. Pins subjected to the test were evaluated for thermally induced cracking and resistance to soldering of the tungsten cladding.

Effect of intracoronary nitroprusside injection on flow recovery during primary PCI in acute STEMI patients.

PubMed

Yang, Lixia; Mu, Lihua; Sun, Linhui; Qi, Feng; Guo, Ruiwei

2017-04-01

The no/slow reflow phenomenon during primary percutaneous coronary intervention (PPCI) causes the destruction of the coronary microcirculation and further myocardial damage. Some studies have shown that intracoronary nitroprusside infusion is a safe and effective method for managing the no/slow reflow phenomenon. However, it is uncertain whether the injection of nitroprusside at a specific time point during PPCI can most effectively prevent no-reflow. In this study, we investigated the effect of the timing of an intracoronary nitroprusside injection on flow recovery during PPCI in patients with ST elevation acute myocardial infarction (STEMI). One hundred twenty consecutive patients with STEMI who underwent PPCI were enrolled in the study. Patients who fulfilled the eligibility criteria were randomly allocated to three groups: control group (N.=40) received no nitroprusside before they completed PCI; the second group (N.=40) received nitroprusside before balloon dilatation; and the third group (N.=40) received nitroprusside after each balloon dilatation and before contrast agent refilling. The baseline clinical variables and the details of the PCI procedure were collected. The thrombolysis in myocardial infarction (TIMI) flow grades and the corrected TIMI frame count (cTFC) were evaluated immediately after stent implantation was completed. There were no significant differences in the baseline characteristics, antithrombotic drugs given before PCI, and details of the PCI procedure among the three groups (P>0.05). The incidence of TIMI grade 3 after PCI was significantly higher in the nitroprusside group than in the control group (P=0.025), whereas cTFC was significantly lower in the nitroprusside group (26.6±15.2) than in the control group (38.1±21.3, P=0.001). The incidence of TIMI grade 3 after PCI was significantly higher in the third group than in the second group (P=0.045), and cTFC was significantly lower in the third group (21.5±9.5) than in the second group (31.2±18.3, P=0.002). Multivariable linear regression analyses showed that the intracoronary nitroprusside injection time was a significant predictor of cTFC after PCI. These data suggest that the intracoronary injection of nitroprusside significantly reduced the incidence of no/slow reflow during PPCI. The intracoronary injection of nitroprusside most effectively prevented the no/slow reflow phenomenon when administered between balloon dilatation and contrast agent refilling during PPCI.

30 CFR 75.1106 - Welding, cutting, or soldering with arc or flame underground.

Code of Federal Regulations, 2010 CFR

2010-07-01

... 30 Mineral Resources 1 2010-07-01 2010-07-01 false Welding, cutting, or soldering with arc or... Protection § 75.1106 Welding, cutting, or soldering with arc or flame underground. [Statutory Provisions] All welding, cutting, or soldering with arc or flame in all underground areas of a coal mine shall, whenever...

Efforts to Develop a 300°C Solder

DOE Office of Scientific and Technical Information (OSTI.GOV)

Norann, Randy A

2015-01-25

This paper covers the efforts made to find a 300°C electrical solder solution for geothermal well monitoring and logging tools by Perma Works LLC. This paper covers: why a high temperature solder is needed, what makes for a good solder, testing flux, testing conductive epoxy and testing intermetallic bonds. Future areas of research are suggested.

21 CFR 189.240 - Lead solders.

Code of Federal Regulations, 2014 CFR

2014-04-01

... 21 Food and Drugs 3 2014-04-01 2014-04-01 false Lead solders. 189.240 Section 189.240 Food and...-Contact Surfaces § 189.240 Lead solders. (a) Lead solders are alloys of metals that include lead and are used in the construction of metal food cans. (b) Food packaged in any container that makes use of lead...

21 CFR 189.240 - Lead solders.

Code of Federal Regulations, 2013 CFR

2013-04-01

... 21 Food and Drugs 3 2013-04-01 2013-04-01 false Lead solders. 189.240 Section 189.240 Food and... Addition to Human Food Through Food-Contact Surfaces § 189.240 Lead solders. (a) Lead solders are alloys of metals that include lead and are used in the construction of metal food cans. (b) Food packaged in any...

21 CFR 189.240 - Lead solders.

Code of Federal Regulations, 2011 CFR

2011-04-01

... 21 Food and Drugs 3 2011-04-01 2011-04-01 false Lead solders. 189.240 Section 189.240 Food and... Addition to Human Food Through Food-Contact Surfaces § 189.240 Lead solders. (a) Lead solders are alloys of metals that include lead and are used in the construction of metal food cans. (b) Food packaged in any...

21 CFR 189.240 - Lead solders.

Code of Federal Regulations, 2012 CFR

2012-04-01

... 21 Food and Drugs 3 2012-04-01 2012-04-01 false Lead solders. 189.240 Section 189.240 Food and... Addition to Human Food Through Food-Contact Surfaces § 189.240 Lead solders. (a) Lead solders are alloys of metals that include lead and are used in the construction of metal food cans. (b) Food packaged in any...

21 CFR 189.240 - Lead solders.

Code of Federal Regulations, 2010 CFR

2010-04-01

... 21 Food and Drugs 3 2010-04-01 2009-04-01 true Lead solders. 189.240 Section 189.240 Food and... Addition to Human Food Through Food-Contact Surfaces § 189.240 Lead solders. (a) Lead solders are alloys of metals that include lead and are used in the construction of metal food cans. (b) Food packaged in any...

Anomalous creep in Sn-rich solder joints

DOE Office of Scientific and Technical Information (OSTI.GOV)

Song, Ho Geon; Morris Jr., John W.; Hua, Fay

2002-03-15

This paper discusses the creep behavior of example Sn-rich solders that have become candidates for use in Pb-free solder joints. The specific solders discussed are Sn-3.5Ag, Sn-3Ag-0.5Cu, Sn-0.7Cu and Sn-10In-3.1Ag, used in thin joints between Cu and Ni-Au metallized pads.

30 CFR 75.1106 - Welding, cutting, or soldering with arc or flame underground.

Code of Federal Regulations, 2013 CFR

2013-07-01

... 30 Mineral Resources 1 2013-07-01 2013-07-01 false Welding, cutting, or soldering with arc or... Protection § 75.1106 Welding, cutting, or soldering with arc or flame underground. [Statutory Provisions] All welding, cutting, or soldering with arc or flame in all underground areas of a coal mine shall, whenever...

30 CFR 75.1106 - Welding, cutting, or soldering with arc or flame underground.

Code of Federal Regulations, 2011 CFR

2011-07-01

... 30 Mineral Resources 1 2011-07-01 2011-07-01 false Welding, cutting, or soldering with arc or... Protection § 75.1106 Welding, cutting, or soldering with arc or flame underground. [Statutory Provisions] All welding, cutting, or soldering with arc or flame in all underground areas of a coal mine shall, whenever...

30 CFR 75.1106 - Welding, cutting, or soldering with arc or flame underground.

Code of Federal Regulations, 2014 CFR

2014-07-01

... 30 Mineral Resources 1 2014-07-01 2014-07-01 false Welding, cutting, or soldering with arc or... Protection § 75.1106 Welding, cutting, or soldering with arc or flame underground. [Statutory Provisions] All welding, cutting, or soldering with arc or flame in all underground areas of a coal mine shall, whenever...

30 CFR 75.1106 - Welding, cutting, or soldering with arc or flame underground.

Code of Federal Regulations, 2012 CFR

2012-07-01

... 30 Mineral Resources 1 2012-07-01 2012-07-01 false Welding, cutting, or soldering with arc or... Protection § 75.1106 Welding, cutting, or soldering with arc or flame underground. [Statutory Provisions] All welding, cutting, or soldering with arc or flame in all underground areas of a coal mine shall, whenever...

Thermo-Mechanical Response of Monolithic and NiTi Shape Memory Alloy Fiber Reinforced Sn-3.8Ag-0.7Cu Solder

DTIC Science & Technology

2005-09-01

novel adaptive Tin-Silver-Copper ( SnAgCu ) solder reinforced with NiTi shape-memory alloy (particles or fiber) developed. An experimental...to meet the demands of miniaturization and enhanced performance in severe environments, a novel adaptive Tin-Silver-Copper ( SnAgCu ) solder...4. Crack region of SnAgCu solder after TMF, from reference [1] ............. 5 Figure 5. Phase diagram of 95.5Sn-3.8Ag-0.7Cu solder, from reference

Method for making a high current fiber brush collector

NASA Astrophysics Data System (ADS)

Scuro, S. J.

1986-05-01

An axial-type homopolar motor having high density, high current fiber brush collectors affording efficient, low contact resistance and low operating temperatures is discussed. The collectors include a ring of concentric row of brushes in equally spaced beveled holes soldered in place using a fixture for heating the ring to just below the solder melting point at a soldering iron for the local application of additional heat at each brush. Prior to soldering, an oxide film is formed on the surfaces of the brushes and ring, and the bevels are burnished to form a wetting surface. Flux applied with the solder at each bevel removes to an effective soldering depth the oxide film on the brushes and the holes.

An Accelerated Method for Soldering Testing

DOE Office of Scientific and Technical Information (OSTI.GOV)

Han, Qingyou; Xu, Hanbing; Ried, Paul

2007-01-01

An accelerated method for testing die soldering has been developed. High intensity ultrasonic vibrations have been applied to simulate the die casting conditions such as high pressure and high molten metal velocity on the pin. The soldering tendency of steels and coated pins has been examined. The results suggest that in the low carbon steel/Al system, the onset of soldering is 60 times faster with ultrasonic vibration than that without ultrasonic vibration. In the H13/A380 system, the onset of soldering reaction is accelerated to between 30-60 times. Coatings significantly reduce the soldering tendency. For purposes of this study, several commercialmore » coatings from Balzers demonstrated the potential for increasing the service life of core pins between 15 and 180 times.« less

Soldering Tool for Integrated Circuits

NASA Technical Reports Server (NTRS)

Takahashi, Ted H.

1987-01-01

Many connections soldered simultaneously in confined spaces. Improved soldering tool bonds integrated circuits onto printed-circuit boards. Intended especially for use with so-called "leadless-carrier" integrated circuits.

Brightness field distributions of microlens arrays using micro molding.

PubMed

Cheng, Hsin-Chung; Huang, Chiung-Fang; Lin, Yi; Shen, Yung-Kang

2010-12-20

This study describes the brightness field distributions of microlens arrays fabricated by micro injection molding (μIM) and micro injection-compression molding (μICM). The process for fabricating microlens arrays used room-temperature imprint lithography, photoresist reflow, electroforming, μIM, μICM, and optical properties measurement. Analytical results indicate that the brightness field distribution of the molded microlens arrays generated by μICM is better than those made using μIM. Our results further demonstrate that mold temperature is the most important processing parameter for brightness field distribution of molded microlens arrays made by μIM or μICM.

Optimal parameters for laser tissue soldering

NASA Astrophysics Data System (ADS)

McNally-Heintzelman, Karen M.; Sorg, Brian S.; Chan, Eric K.; Welch, Ashley J.; Dawes, Judith M.; Owen, Earl R.

1998-07-01

Variations in laser irradiance, exposure time, solder composition, chromophore type and concentration have led to inconsistencies in published results of laser-solder repair of tissue. To determine optimal parameters for laser tissue soldering, an in vitro study was performed using an 808-nm diode laser in conjunction with an indocyanine green (ICG)- doped albumin protein solder to weld bovine aorta specimens. Liquid and solid protein solders prepared from 25% and 60% bovine serum albumin (BSA), respectively, were compared. The effects of laser irradiance and exposure time on tensile strength of the weld and temperature rise as well as the effect of hydration on bond stability were investigated. Optimum irradiance and exposure times were identified for each solder type. Increasing the BSA concentration from 25% to 60% greatly increased the tensile strength of the weld. A reduction in dye concentration from 2.5 mg/ml to 0.25 mg/ml was also found to result in an increase in tensile strength. The strongest welds were produced with an irradiance of 6.4 W/cm2 for 50 s using a solid protein solder composed of 60% BSA and 0.25 mg/ml ICG. Steady-state solder surface temperatures were observed to reach 85 plus or minus 5 degrees Celsius with a temperature gradient across the solid protein solder strips of between 15 and 20 degrees Celsius. Finally, tensile strength was observed to decrease significantly (20 to 25%) after the first hour of hydration in phosphate-buffered saline. No appreciable change was observed in the strength of the tissue bonds with further hydration.

Finite Element-Assisted Assessment of the Thermo-cyclic Characteristics of Leads Soldered with SnAgCu(+Bi,In) Alloys

NASA Astrophysics Data System (ADS)

Lis, Adrian; Nakanishi, Kohei; Matsuda, Tomoki; Sano, Tomokazu; Minagawa, Madoka; Okamoto, Masahide; Hirose, Akio

2017-07-01

Solder joints between leads and printed circuit boards in thin small outline packages were produced with conventional Sn1.0Ag0.7Cu (SAC107) and Sn3.0Ag0.7Cu (SAC305) solders as well as various solder alloys with gradually increasing amounts of Bi (up to 3.0 wt.%) and In (up to 1.0 wt.%) within the SAC107 base solder. The reliability of soldered leads in temperature cycle (TC) tests improved most with solder alloys containing both Bi (1.6 wt.%) and In (0.5 wt.%). Microindentation and electron probe microanalysis mappings revealed that the effect originates from a combination of solution and precipitation strengthening of the initial SAC alloy. The distribution of inelastic strain accumulation (ISA), as a measure for degradation, was determined in the solder joints by finite element calculations. It was shown that defects in the solder proximal to the lead (<60-75 μm) strongly impact the reliability and provoke crack initiation around the defect where the highest ISA is located. In particular, similar TC performance can be expected for defect-free joints and for those whose defects exceed the threshold distance from the lead (>60-75 μm), which was underpinned by similar cracking characteristics along the lead-solder interface. The ISA was confirmed to be lower in SAC+Bi/In alloys owing to their enhanced elasto-plastic properties. Moreover, the addition of a thin Cu coating on the leads could improve the joint reliability, as suggested by the calculation of the ISA and the acceleration factor.

Morphology and Shear Strength of Lead-Free Solder Joints with Sn3.0Ag0.5Cu Solder Paste Reinforced with Ceramic Nanoparticles

NASA Astrophysics Data System (ADS)

Yakymovych, A.; Plevachuk, Yu.; Švec, P.; Švec, P.; Janičkovič, D.; Šebo, P.; Beronská, N.; Roshanghias, A.; Ipser, H.

2016-12-01

To date, additions of different oxide nanoparticles is one of the most widespread procedures to improve the mechanical properties of metals and metal alloys. This research deals with the effect of minor ceramic nanoparticle additions (SiO2, TiO2 and ZrO2) on the microstructure and mechanical properties of Cu/solder/Cu joints. The reinforced Sn3.0Ag0.5Cu (SAC305) solder alloy with 0.5 wt.% and 1.0 wt.% of ceramic nanoparticles was prepared through mechanically stirring. The microstructure of as-solidified Cu/solder/Cu joints was studied using scanning electron microscopy. The additions of ceramic nanoparticles suppressed the growth of the intermetallic compound layer Cu6Sn5 at the interface solder/Cu and improved the microstructure of the joints. Furthermore, measurements of mechanical properties showed improved shear strength of Cu/composite solder/Cu joints compared to joints with unreinforced solder. This fact related to all investigated ceramic nanoinclusions and should be attributed to the adsorption of nanoparticles on the grain surface during solidification. However, this effect is less pronounced on increasing the nanoinclusion content from 0.5 wt.% to 1.0 wt.% due to agglomeration of nanoparticles. Moreover, a comparison analysis showed that the most beneficial influence was obtained by minor additions of SiO2 nanoparticles into the SAC305 solder alloy.

Dural reconstruction by fascia using a temperature-controlled CO2 laser soldering system

NASA Astrophysics Data System (ADS)

Forer, Boaz; Vasilyev, Tamar; Brosh, Tamar; Kariv, Naam; Gil, Ziv; Fliss, Dan M.; Katzir, Abraham

2005-04-01

Conventional methods for dura repair are normally based on sutures or stitches. These methods have several disadvantages: (1) The dura is often brittle, and the standard procedures are difficult and time consuming. (2) The seal is leaky. (3) The introduction of a foreign body (e.g. sutures) may cause an inflammatory response. In order to overcome these difficulties we used a temperature controlled fiber optic based CO2 laser soldering system. In a set of in vitro experiments we generated a hole of diameter 10 mm in the dura of a pig corpse, covered the hole with a segment of fascia, and soldered the fascia to the edges of the hole, using 47% bovine albumin as a solder. The soldering was carried out spot by spot, and each spot was heated to 65° C for 3-6 seconds. The soldered dura was removed and the burst pressure of the soldered patch was measured. The average value for microscopic muscular side soldering was 194 mm Hg. This is much higher than the maximal physiological pressure of the CSF fluid in the brain, which is 15 mm Hg. In a set of in vivo experiments, fascia patches were soldered on holes in five farm pigs. The long term results of these experiments were very promising. In conclusion, we have developed an advanced technique for dural reconstruction, which will find important clinical applications.

Failure Mechanisms of SAC/Fe-Ni Solder Joints During Thermal Cycling

NASA Astrophysics Data System (ADS)

Gao, Li-Yin; Liu, Zhi-Quan; Li, Cai-Fu

2017-08-01

Thermal cycling tests have been conducted on Sn-Ag-Cu/Fe- xNi ( x = 73 wt.% or 45 wt.%) and Sn-Ag-Cu/Cu solder joints according to the Joint Electron Device Engineering Council industrial standard to study their interfacial reliability under thermal stress. The interfacial intermetallic compounds formed for solder joints on Cu, Fe-73Ni, and Fe-45Ni were 4.5 μm, 1.7 μm, and 1.4 μm thick, respectively, after 3000 cycles, demonstrating excellent diffusion barrier effect of Fe-Ni under bump metallization (UBM). Also, two deformation modes, viz. solder extrusion and fatigue crack formation, were observed by scanning electron microscopy and three-dimensional x-ray microscopy. Solder extrusion dominated for solder joints on Cu, while fatigue cracks dominated for solder joints on Fe-45Ni and both modes were detected for those on Fe-73Ni. Solder joints on Fe-Ni presented inferior reliability during thermal cycling compared with those on Cu, with characteristic lifetime of 3441 h, 3190 h, and 1247 h for Cu, Fe-73Ni, and Fe-45Ni UBM, respectively. This degradation of the interfacial reliability for solder joints on Fe-Ni is attributed to the mismatch in coefficient of thermal expansion (CTE) at interconnection level. The CTE mismatch at microstructure level was also analyzed by electron backscatter diffraction for clearer identification of recrystallization-related deformation mechanisms.

The Shear Strength and Fracture Behavior of Sn-Ag- xSb Solder Joints with Au/Ni-P/Cu UBM

NASA Astrophysics Data System (ADS)

Lee, Hwa-Teng; Hu, Shuen-Yuan; Hong, Ting-Fu; Chen, Yin-Fa

2008-06-01

This study investigates the effects of Sb addition on the shear strength and fracture behavior of Sn-Ag-based solders with Au/Ni-P/Cu underbump metallization (UBM) substrates. Sn-3Ag- xSb ternary alloy solder joints were prepared by adding 0 wt.% to 10 wt.% Sb to a Sn-3.5Ag alloy and joining them with Au/Ni-P/Cu UBM substrates. The solder joints were isothermally stored at 150°C for up to 625 h to study their microstructure and interfacial reaction with the UBM. Single-lap shear tests were conducted to evaluate the mechanical properties, thermal resistance, and failure behavior. The results show that UBM effectively suppressed intermetallic compound (IMC) formation and growth during isothermal storage. The Sb addition helped to refine the Ag3Sn compounds, further improving the shear strength and thermal resistance of the solders. The fracture behavior evolved from solder mode toward the mixed mode and finally to the IMC mode with increasing added Sb and isothermal storage time. However, SnSb compounds were found in the solder with 10 wt.% Sb; they may cause mechanical degradation of the solder after long-term isothermal storage.

Evaluation of ENEPIG and Immersion Silver Surface Finishes Under Drop Loading

NASA Astrophysics Data System (ADS)

Pearl, Adam; Osterman, Michael; Pecht, Michael

2016-01-01

The effect of printed circuit board surface finish on the drop loading reliability of ball grid array (BGA) solder interconnects has been examined. The finishes examined include electroless nickel/electroless palladium/immersion gold (ENEPIG) and immersion silver (ImAg). For the ENEPIG finish, the effect of the Pd plating layer thickness was evaluated by testing two different thicknesses: 0.05 μm and 0.15 μm. BGA components were assembled onto the boards using either eutectic Sn-Pb or Sn-3.0Ag-0.5Cu (SAC305) solder. Prior to testing, the assembled boards were aged at 100°C for 24 h or 500 h. The boards were then subjected to multiple 1500-g drop tests. Failure analysis indicated the primary failure site for the BGAs to be the solder balls at the board-side solder interface. Cratering of the board laminate under the solder-attached pads was also observed. In all cases, isothermal aging reduced the number of drops to failure. The components soldered onto the boards with the 0.15- μm-Pd ENEPIG finish with the SAC305 solder had the highest characteristic life, at 234 drops to failure, compared with the other finish-solder combinations.

Sn-Ag-Cu Nanosolders: Solder Joints Integrity and Strength

NASA Astrophysics Data System (ADS)

Roshanghias, Ali; Khatibi, Golta; Yakymovych, Andriy; Bernardi, Johannes; Ipser, Herbert

2016-08-01

Although considerable research has been dedicated to the synthesis and characterization of lead-free nanoparticle solder alloys, only very little has been reported on the reliability of the respective joints. In fact, the merit of nanoparticle solders with depressed melting temperatures close to the Sn-Pb eutectic temperature has always been challenged when compared with conventional solder joints, especially in terms of inferior solderability due to the oxide shell commonly present on the nanoparticles, as well as due to compatibility problems with common fluxing agents. Correspondingly, in the current study, Sn-Ag-Cu (SAC) nanoparticle alloys were combined with a proper fluxing vehicle to produce prototype nanosolder pastes. The reliability of the solder joints was successively investigated by means of electron microscopy and mechanical tests. As a result, the optimized condition for employing nanoparticles as a competent nanopaste and a novel procedure for surface treatment of the SAC nanoparticles to diminish the oxide shell prior to soldering are being proposed.

Microstructure and mechanical behavior of low-melting point Bi-Sn-In solder joints

NASA Astrophysics Data System (ADS)

Nguyen, Van Luong; Kim, Sang Hoon; Jeong, Jae Won; Lim, Tae-Soo; Yang, Dong-Yeol; Kim, Ki Bong; Kim, Young Ja; Lee, Jun Hong; Kim, Yong-Jin; Yang, Sangsun

2017-09-01

Ternary Bi-31.5Sn-25.0In solder has been proposed and studied for application in temperature-sensitive electronic components. In a Bi-31.5Sn- 25.0In solder joint, In was detected in an intermetallic compound (IMC) layer formed at the solder/Cu substrate interface with a thickness of 4.8 μm. The microstructure of the bulk solder consisted of Sn-rich phases distributed in Bi-rich phases with dispersion of In in both phases. Meanwhile, the nanomechanical properties of the Bi-31.5Sn-25.0In solder showed great strain rate sensitivity. To be specific, hardness increased from 9.91 MPa to 56.84 MPa as the strain rate increased in the range of (0.0005-0.125) s-1. The strain-rate sensitivity exponent ( m) was found to be 0.28, indicating that the excellent ductility was shown for the solder tested under the present conditions. [Figure not available: see fulltext.

Interfacial Phenomena in Al/Al, Al/Cu, and Cu/Cu Joints Soldered Using an Al-Zn Alloy with Ag or Cu Additions

NASA Astrophysics Data System (ADS)

Pstruś, Janusz; Gancarz, Tomasz

2014-05-01

The studies of soldered joints were carried out in systems: Al/solder/Al, Al/solder/Cu, Cu/solder/Cu, where the solder was (Al-Zn)EUT, (Al-Zn)EUT with 0.5, 1.0, and 1.5 at.% of Ag and (Al-Zn)EUT with 0.5, 1.0, and 1.5 at.% of Cu addition. Brazing was performed at 500 °C for 3 min. The EDS analysis indicated that the composition of the layers starting from the Cu pad was CuZn, Cu5Zn8, and CuZn4, respectively. Wetting tests were performed at 500 °C for 3, 8, 15, and 30 min, respectively. Thickness of the layers and their kinetics of growth were measured based on the SEM micrographs. The formation of interlayers was not observed from the side of Al pads. On the contrary, dissolution of the Al substrate and migration of Al-rich particles into the bulk of the solder were observed.

Microstructural evolution and IMCs growth behavior of Sn-58Bi-0.25Mo solder joint during aging treatment

NASA Astrophysics Data System (ADS)

Yang, Li; Zhu, Lu; Zhang, Yaocheng; Zhou, Shiyuan; Xiong, Yifeng; Wu, Pengcheng

2018-02-01

The microstructural evolution and IMCs growth behavior of Sn-58Bi and Sn-58Bi-0.25Mo solder joints were investigated. The results showed that the microstructure is coarsened, the IMCs layer thickness is increased and the tensile strength of Sn-58Bi and Sn-58Bi-0.25Mo solder joints is decreased with increasing aging time and temperature. Aging temperature is the key factor that causes the excessive IMCs growth of the solder joint compared with aging time, and the activation energy of IMCs layer growth of Sn-58Bi and Sn-58Bi-0.25Mo solder joints is 48.94 kJ mol-1 and 53.79 kJ mol-1, respectively. During the aging treatment, the microstructure of Sn-58Bi solder joint is refined by adding Mo nanoparticles, and the appropriate IMCs layer thickness and improved mechanical properties are obtained by Sn-58Bi-0.25Mo solder joint.

Histologic assessment of mesh fixation following laser-assisted tissue soldering in a lapine model.

PubMed

Lanzafame, Raymond J; Brondon, Philip; Stadler, Istvan; DeVore, Dale P; Soltz, Robert; Soltz, Barbara A

2005-08-01

Wound histology and mesh bioincorporation following intraperitoneal fixation using laser-assisted soldering was evaluated. 2.8-3.2 kg NZW rabbits underwent laparotomy. Controls had 2x2 cm segments of Mersilene stapled to peritoneum. Group 2 segments were affixed with 55% collagen solder onlay by fiber-coupled diode laser (1.43 +/- 10 micro, 2.5 W CW, 4 mm spot, 60 degrees C set temperature). Group 4 had Mersilene inlaid into melted solder. Group 3 had solder-embedded Vicryl mesh affixed. Animals were euthanized at 0, 2, 4, 6 weeks. Fixed sections were assessed for integrity, inflammation, and fibrosis using H & E, Masson's Trichrome and Evans Van Gieson staining. Histology demonstrated cell types, local mesh reaction, and progressive evidence of solder reabsorption mimicking normal healing and bioincorporation. Mersilene groups demonstrated normal arrangement of collagen-rich layers around mesh. Collagen-based tissue soldering permits normal wound healing and may mitigate use of staples. Further development of this strategy is warranted. (c) 2005 Wiley-Liss, Inc.

Intermetallic compounds in 3D integrated circuits technology: a brief review

NASA Astrophysics Data System (ADS)

Annuar, Syahira; Mahmoodian, Reza; Hamdi, Mohd; Tu, King-Ning

2017-12-01

The high performance and downsizing technology of three-dimensional integrated circuits (3D-ICs) for mobile consumer electronic products have gained much attention in the microelectronics industry. This has been driven by the utilization of chip stacking by through-Si-via and solder microbumps. Pb-free solder microbumps are intended to replace conventional Pb-containing solder joints due to the rising awareness of environmental preservation. The use of low-volume solder microbumps has led to crucial constraints that cause several reliability issues, including excessive intermetallic compounds (IMCs) formation and solder microbump embrittlement due to IMCs growth. This article reviews technologies related to 3D-ICs, IMCs formation mechanisms and reliability issues concerning IMCs with Pb-free solder microbumps. Finally, future outlook on the potential growth of research in this area is discussed.

Intermetallic compounds in 3D integrated circuits technology: a brief review.

PubMed

Annuar, Syahira; Mahmoodian, Reza; Hamdi, Mohd; Tu, King-Ning

2017-01-01

The high performance and downsizing technology of three-dimensional integrated circuits (3D-ICs) for mobile consumer electronic products have gained much attention in the microelectronics industry. This has been driven by the utilization of chip stacking by through-Si-via and solder microbumps. Pb-free solder microbumps are intended to replace conventional Pb-containing solder joints due to the rising awareness of environmental preservation. The use of low-volume solder microbumps has led to crucial constraints that cause several reliability issues, including excessive intermetallic compounds (IMCs) formation and solder microbump embrittlement due to IMCs growth. This article reviews technologies related to 3D-ICs, IMCs formation mechanisms and reliability issues concerning IMCs with Pb-free solder microbumps. Finally, future outlook on the potential growth of research in this area is discussed.

Ultrasonic-assisted soldering of Cu/Ti joints

NASA Astrophysics Data System (ADS)

Cui, Wei; Wang, Chunyu; Li, Yuhang; Zhong, Tongtong; Yang, Jianguo; Bao, Yefeng

2018-03-01

Cu/Ti joints are expected to be used in various applications, while reliable joining method is still to be developed. It is commonly not possible to solder Ti alloys using Sn-based solder alloys because of their poor wettability. In this study, Sn-Ag-Cu soldering filler metal was used to joining TC4 titanium alloy and pure copper using ultrasonic-assisted soldering. The influence of different temperature and different ultrasonic time on the welded joint is studied and explored. Microstructure of the joints was investigated. Shear strength of the joints reached the maximum value, i.e. 38.2MPa. Relationship between the sonication parameters and the microstructure and strength of the joints was discussed. Thus, it is verified that dissimilar metal brazing of TC4 and copper is suitable for low temperature soldering.

Synthesis of tin, silver and their alloy nanoparticles for lead-free interconnect applications

NASA Astrophysics Data System (ADS)

Jiang, Hongjin

SnPb solders have long been used as interconnect materials in microelectronic packaging. Due to the health threat of lead to human beings, the use of lead-free interconnect materials is imperative. Three kinds of lead-free interconnect materials are being investigated, namely lead-free metal solders (SnAg, SnAgCu, etc.), electrically conductive adhesives (ECAs) and carbon nanotubes (CNTs). However, there are still limitations for the full utilization of these lead-free interconnect materials in the microelectronic packaging, such as higher melting point of lead-free metal solders, lower electrical conductivity of the ECAs and poor adhesion of CNTs to substrates. This thesis is devoted to the research and development of low processing temperature lead-free interconnect materials for microelectronic packaging applications with an emphasis on fundamental studies of nanoparticles synthesis, dispersion and oxidation prevention, and nanocomposites fabrication. Oxide-free tin (Sn), tin/silver (96.5Sn3.5Ag) and tin/silver/copper (96.5Sn3.0Ag0.5Cu) alloy nanoparticles with different sizes were synthesized by a low temperature chemical reduction method. Both size dependent melting point and latent heat of fusion of the synthesized nanoparticles were obtained. The nano lead-free solder pastes/composites created by dispersing the SnAg or SnAgCu alloy nanoparticles into an acidic type flux spread and wet on the cleaned copper surface at 220 to 230°C. This study demonstrated the feasibility of nano sized SnAg or SnAgCu alloy particle pastes for low processing temperature lead-free interconnect applications in microelectronic packaging.

METHOD FOR SOLDERING NORMALLY NON-SOLDERABLE ARTICLES

DOEpatents

McGuire, J.C.

1959-11-24

Methods are presented for coating and joining materials which are considered difficult to solder by utilizing an abrasive wheel and applying a bar of a suitable coating material, such as Wood's metal, to the rotating wheel to fill the cavities of the abrasive wheel and load the wheel with the coating material. The surface of the base material is then rubbed against the loaded rotating wheel, thereby coating the surface with the soft coating metal. The coating is a cohesive bonded layer and holds the base metal as tenaciously as a solder holds to easily solderable metals.

Reduced impedance and superconductivity of SnAgCu solder alloy at high frequency

NASA Astrophysics Data System (ADS)

Yao, Wei; Basaran, Cemal

2012-10-01

Skin effect of lead-free solder joints is investigated over a wide frequency band. Contrary to common believe that `effective impedance of solder alloys increases with frequency', resistance tends to saturate when frequency reaches a critical value, 10 MHz for SAC solder alloys. Negative surface impedance growth rate is observed when employs square waveform AC current loading at high current density. Further increased frequency causes a dramatic reduction of effective resistance. At 11 MHz with current density of 106 A/cm2, effective resistance of solder alloy drops to near zero value.

Natural radioactive contaminants in solder

NASA Astrophysics Data System (ADS)

Bunzl, K.; Kracke, W.

1985-07-01

Comparatively high surface count rates for alpha- and beta-radiation were observed for several solders. They were identified as 210Pb and 210Po. The corresponding specific activities in solder were determined.

Effect of surface finish on the failure mechanisms of flip-chip solder joints under electromigration

NASA Astrophysics Data System (ADS)

Lin, Y. L.; Lai, Y. S.; Tsai, C. M.; Kao, C. R.

2006-12-01

Two substrate surface finishes, Au/Ni and organic solderable preservative (OSP), were used to study the effect of the surface finish on the reliability of flip-chip solder joints under electromigration at 150°C ambient temperature. The solder used was eutectic PbSn, and the applied current density was 5×103 A/cm2 at the contact window of the chip. The under bump metallurgy (UBM) on the chip was sputtered Cu/Ni. It was found that the mean-time-to-failure (MTTF) of the OSP joints was six times better than that of the Au/Ni joints (3080 h vs. 500 h). Microstructure examinations uncovered that the combined effect of current crowding and the accompanying local Joule heating accelerated the local Ni UBM consumption near the point of electron entrance. Once Ni was depleted at a certain region, this region became nonconductive, and the flow of the electrons was diverted to the neighboring region. This neighboring region then became the place where electrons entered the joint, and the local Ni UBM consumption was accelerated. This process repeated itself, and the Ni-depleted region extended further on, creating an ever-larger nonconductive region. The solder joint eventually, failed when the nonconductive region became too large, making the effective current density very high. Accordingly, the key factor determining the MTTF was the Ni consumption rate. The joints with the OSP surface finish had a longer MTTF because Cu released from the substrate was able to reduce the Ni consumption rate.

Effect of varying chromophores used in light-activated protein solders on tensile strength and thermal damage profile of repairs.

PubMed

Hoffman, Grant T; Byrd, Brian D; Soller, Eric C; Heintzelman, Douglas L; McNally-Heintzelman, Karen M

2003-01-01

Clinical adoption of laser tissue welding (LTW) techniques has been beleaguered by problems associated with thermal damage of tissue and insufficient strength of the resulting tissue bond. The magnitude of these problems has been significantly reduced with the incorporation of indocyanine green (ICG)-doped protein solders into the LTW procedure to form a new technique known as laser tissue soldering (LTS). With the addition of ICG, a secondary concern has arisen relating to the potential harmful effects of the degradation products of the chromophore upon thermal denaturation of the protein solder with a laser. In this study, two different food colorings were investigated, including blue #1 and green consisting of yellow #5 and blue #1, as alternative chromophores for use in LTS techniques. Food coloring has been found to have a suitable stability and safety profile for enteral use when heated to temperatures above 200 degrees C; thus, it is a promising candidate chromophore for LTS which typically requires temperatures between 50 degrees C and 100 degrees C. Experimental investigations were conducted to test the tensile strength of ex vivo repairs formed using solders doped with these alternative chromophores in a bovine model. Two commonly used chromophores, ICG and methylene blue (MB), were investigated as a reference. In addition, the temperature rise, depth of thermal coagulation in the protein solder, and the extent of thermal damage in the surrounding tissue were measured. Temperature rise at the solder/tissue interface, and consequently the degree of solder coagulation and collateral tissue thermal damage, was directly related to the penetration depth of laser light in the protein solder. Variation of the chromophore concentration such that the laser light penetrated to a depth approximately equal to half the thickness of the solder resulted in uniform results between each group of chromophores investigated. Optimal tensile strength of repairs was achieved by optimizing laser and solder parameters to obtain a temperature of approximately 65 degrees C at the solder/tissue interface. The two alternative chromophores tested in this study show considerable promise for application in LTS techniques, with equivalent tensile strength to solders doped with ICG or MB, and the potential advantage of eliminating the risks associated with harmful byproducts.

Investigation of corrosion and stress corrosion cracking susceptibility of S30400 and S31600 stainless steels exposed to commercial soldering flux containing zinc chloride

DOE Office of Scientific and Technical Information (OSTI.GOV)

Nguyen, D.T.

1995-10-01

A corrosion investigation was conducted to determine corrosion behavior and stress corrosion cracking (SCC) susceptibility of S30400 and S31600 stainless steel exposed to soldering flux paste containing 25 wt% zinc chloride. Electrochemical test results indicated that soldering flux paste was not corrosive to S30400 and S31600 at room temperature. The wax phase (light phase) of soldering flux was also not corrosive to S30400 and S31600. However, the heavy phase of solder flux was corrosive to S30400 and S31600 at elevated temperatures. In heavy phase, S30400 did not passivate, while S31600 passivated at temperatures up to 80 C while no passivitymore » was observed at 85 C and above. AC impedance test results showed that S30400 and S31600 corroded at rates of less than 0.1 mpy in solder flux pastes at room temperature. In the soldering flux heavy phase, corrosion rates were about 2 mpy or less for S30400 at temperatures up to 75 C and S31600 at temperatures up to 70 C. However, corrosion rates of S30400 in the soldering flux heavy phase increased to 5, 8, 10, and 22 mpy at 80, 85, 90, and 95 C while corrosion rates of S31600 sst in the soldering flux heavy phase increased to 4, 5, 7, and 11, and 30 mpy at 75, 80, 85, 90 and 95 C, respectively. CERT results revealed that no SCC susceptibility when S30400 and S31600 were exposed to soldering flux paste at room temperature and wax phase at 65 and 95 C. However, both test alloys were susceptible to transgranular SCC when exposed to the soldering flux heavy phase at temperatures of 65+ C. Severity of SCC increased with temperature increase. SCC fractures were characterized by reduction of ductility and numerous SCC secondary cracks on the specimen gage length. The most severe SCC fracture was observed on a S30400 specimen partially submersed in the soldering flux heavy phase and partially submersed in the soldering flux wax phase at 95 C. No similar cracking was observed on S31600.« less

Facilitating NASA's Use of GEIA-STD-0005-1, Performance Standard for Aerospace and High Performance Electronic Systems Containing Lead-Free Solder

NASA Technical Reports Server (NTRS)

Plante, Jeannete

2010-01-01

GEIA-STD-0005-1 defines the objectives of, and requirements for, documenting processes that assure customers and regulatory agencies that AHP electronic systems containing lead-free solder, piece parts, and boards will satisfy the applicable requirements for performance, reliability, airworthiness, safety, and certify-ability throughout the specified life of performance. It communicates requirements for a Lead-Free Control Plan (LFCP) to assist suppliers in the development of their own Plans. The Plan documents the Plan Owner's (supplier's) processes, that assure their customer, and all other stakeholders that the Plan owner's products will continue to meet their requirements. The presentation reviews quality assurance requirements traceability and LFCP template instructions.

Design and fabrication of lanthanum-doped tin-silver-copper lead-free solder for the next generation of microelectronics applications in severe environment

NASA Astrophysics Data System (ADS)

Sadiq, Muhammad

Tin-Lead solder (Sn-Pb) has long been used in the Electronics industry. But, due to its toxic nature and environmental effects, certain restrictions are made on its use by the European Rehabilitation of Hazardous Substances (RoHS) directive, and therefore, many researchers are looking to replace it. The urgent need for removing lead from solder alloys led to the very fast introduction of lead-free solder alloys without a deep knowledge of their behavior. Therefore, an extensive knowledge and understanding of the mechanical behavior of the emerging generation of lead-free solders is required to satisfy the demands of structural reliability. Sn-Ag-Cu (SAC) solders are widely used as lead-free replacements but their coarse microstructure and formation of hard and brittle Inter-Metallic Compounds (IMCs) have limited their use in high temperature applications. Many additives are studied to refine the microstructure and improve the mechanical properties of SAC solders including iron (Fe), bismuth (Bi), antimony (Sb) and indium (In) etc. Whereas many researchers studied the impact of novel rare earth (RE) elements like lanthanum (La), cerium (Ce) and lutetium (Lu) on SAC solders. These RE elements are known as “vitamins of metals” because of their special surface active properties. They reduce the surface free energy, refine the grain size and improve the mechanical properties of many lead free solder alloys like Sn-Ag, Sn-Cu and SAC but still a systematic study is required to explore the special effects of “La” on the eutectic SAC alloys. The objective of this PhD thesis is to extend the current knowledge about lead free solders of SAC alloys towards lanthanum doping with varying environmental conditions implemented during service. This thesis is divided into six main parts.

49 CFR 393.67 - Liquid fuel tanks.

Code of Federal Regulations, 2012 CFR

2012-10-01

..., by brazing, by silver soldering, or by techniques which provide heat resistance and mechanical... soldering with a lead-based or other soft solder. (2) Fittings. The fuel tank body must have flanges or...

49 CFR 393.67 - Liquid fuel tanks.

Code of Federal Regulations, 2011 CFR

2011-10-01

..., by brazing, by silver soldering, or by techniques which provide heat resistance and mechanical... soldering with a lead-based or other soft solder. (2) Fittings. The fuel tank body must have flanges or...

49 CFR 393.67 - Liquid fuel tanks.

Code of Federal Regulations, 2013 CFR

2013-10-01

..., by brazing, by silver soldering, or by techniques which provide heat resistance and mechanical... soldering with a lead-based or other soft solder. (2) Fittings. The fuel tank body must have flanges or...

Acid soldering flux poisoning

MedlinePlus

Acid soldering flux is a chemical used to clean and protect the area where two pieces of metal are ... The harmful substances in soldering fluxes are called hydrocarbons. They include: Ammonium chloride Rosin Hydrochloric acid Zinc chloride

49 CFR 393.67 - Liquid fuel tanks.

Code of Federal Regulations, 2014 CFR

2014-10-01

..., by brazing, by silver soldering, or by techniques which provide heat resistance and mechanical... soldering with a lead-based or other soft solder. (2) Fittings. The fuel tank body must have flanges or...

Intermetallic compounds in 3D integrated circuits technology: a brief review

PubMed Central

Annuar, Syahira; Mahmoodian, Reza; Hamdi, Mohd; Tu, King-Ning

2017-01-01

Abstract The high performance and downsizing technology of three-dimensional integrated circuits (3D-ICs) for mobile consumer electronic products have gained much attention in the microelectronics industry. This has been driven by the utilization of chip stacking by through-Si-via and solder microbumps. Pb-free solder microbumps are intended to replace conventional Pb-containing solder joints due to the rising awareness of environmental preservation. The use of low-volume solder microbumps has led to crucial constraints that cause several reliability issues, including excessive intermetallic compounds (IMCs) formation and solder microbump embrittlement due to IMCs growth. This article reviews technologies related to 3D-ICs, IMCs formation mechanisms and reliability issues concerning IMCs with Pb-free solder microbumps. Finally, future outlook on the potential growth of research in this area is discussed. PMID:29057024

Ductile fracture mechanism of low-temperature In-48Sn alloy joint under high strain rate loading.

PubMed

Kim, Jong-Woong; Jung, Seung-Boo

2012-04-01

The failure behaviors of In-48Sn solder ball joints under various strain rate loadings were investigated with both experimental and finite element modeling study. The bonding force of In-48Sn solder on an Ni plated Cu pad increased with increasing shear speed, mainly due to the high strain-rate sensitivity of the solder alloy. In contrast to the cases of Sn-based Pb-free solder joints, the transition of the fracture mode from a ductile mode to a brittle mode was not observed in this solder joint system due to the soft nature of the In-48Sn alloy. This result is discussed in terms of the relationship between the strain-rate of the solder alloy, the work-hardening effect and the resulting stress concentration at the interfacial regions.

The effects of additives to SnAgCu alloys on microstructure and drop impact reliability of solder joints

NASA Astrophysics Data System (ADS)

Liu, Weiping; Lee, Ning-Cheng

2007-07-01

The impact reliability of solder joints in electronic packages is critical to the lifetime of electronic products, especially those portable devices using area array packages such as ball-grid array (BGA) and chip-scale packages (CSP). Currently, SnAgCu (SAC) solders are most widely used for lead-free applications. However, BGA and CSP solder joints using SAC alloys are fragile and prone to premature interfacial failure, especially under shock loading. To further enhance impact reliability, a family of SAC alloys doped with a small amount of additives such as Mn, Ce, Ti, Bi, and Y was developed. The effects of doping elements on drop test performance, creep resistance, and microstructure of the solder joints were investigated, and the solder joints made with the modified alloys exhibited significantly higher impact reliability.

Ceramic ball grid array package stress analysis

NASA Astrophysics Data System (ADS)

Badri, S. H. B. S.; Aziz, M. H. A.; Ong, N. R.; Sauli, Z.; Alcain, J. B.; Retnasamy, V.

2017-09-01

The ball grid array (BGA), a form of chip scale package (CSP), was developed as one of the most advanced surface mount devices, which may be assembled by an ordinary surface ball bumps are used instead of plated nickel and gold (Ni/Au) bumps. Assembly and reliability of the BGA's printed circuit board (PCB), which is soldered by conventional surface mount technology is considered in this study. The Ceramic Ball Grid Array (CBGA) is a rectangular ceramic package or square-shaped that will use the solder ball for external electrical connections instead of leads or wire for connections. The solder balls will be arranged in an array or grid at the bottom of the ceramic package body. In this study, ANSYS software is used to investigate the stress on the package for 2 balls and 4 balls of the CBGA package with the various force range of 1-3 Newton applied to the top of the die, top of the substrate and side of the substrate. The highest maximum stress was analyzed and the maximum equivalent stress was observed on the solder ball and the die. From the simulation result, the CBGA package with less solder balls experience higher stress compared to the package with many solder balls. Therefore, less number of solder ball on the CBGA package results higher stress and critically affect the reliability of the solder balls itself, substrate and die which can lead to the solder crack and also die crack.

Determination of Anand parameters for SnAgCuCe solder

NASA Astrophysics Data System (ADS)

Zhang, Liang; Xue, Songbai; Gao, Lili; Zeng, Guang; Sheng, Zhong; Chen, Yan; Yu, Shenglin

2009-10-01

A unified viscoplastic constitutive model, Anand equations, was used to represent the inelastic deformation behavior for Sn3.8Ag0.7Cu/Sn3.8Ag0.7 Cu0.03Ce solders in surface mount technology. The Anand parameters of the constitutive equations for the SnAgCu and SnAgCuCe solders were determined from separated constitutive relations and experimental results. Non-linear least-squares fitting was selected to determine the model constants. Comparisons were then made with experimental measurements of the stress-inelastic strain curves: excellent agreement was found. The model accurately predicted the overall trend of steady-state stress-strain behavior of SnAgCu and SnAgCuCe solders for the temperature ranges from -55 to 125 °C and for the strain rate range from 1% s-1 to 0.01% s-1. It is concluded that the Anand model can be applied to represent the inelastic deformation behavior of solders at high homologous temperatures and can be recommended for finite element simulation of the stress-strain response of lead-free soldered joints. Based on the Anand model, the investigations of thermo-mechanical behavior of SnAgCu and SnAgCuCe soldered joints in fine pitch quad flat package by the finite element code have been done under thermal cyclic loading, and it is found that the reliability of the SnAgCuCe soldered joints is better than that of the SnAgCu soldered joints.

Solderability test system

DOEpatents

Yost, Fred; Hosking, Floyd M.; Jellison, James L.; Short, Bruce; Giversen, Terri; Reed, Jimmy R.

1998-01-01

A new test method to quantify capillary flow solderability on a printed wiring board surface finish. The test is based on solder flow from a pad onto narrow strips or lines. A test procedure and video image analysis technique were developed for conducting the test and evaluating the data. Feasibility tests revealed that the wetted distance was sensitive to the ratio of pad radius to line width (l/r), solder volume, and flux predry time.

Fast formation and growth of high-density Sn whiskers in Mg/Sn-based solder/Mg joints by ultrasonic-assisted soldering: Phenomena, mechanism and prevention.

PubMed

Li, M Y; Yang, H F; Zhang, Z H; Gu, J H; Yang, S H

2016-06-08

A universally applicable method for promoting the fast formation and growth of high-density Sn whiskers on solders was developed by fabricating Mg/Sn-based solder/Mg joints using ultrasonic-assisted soldering at 250 °C for 6 s and then subjected to thermal aging at 25 °C for 7 d. The results showed that the use of the ultrasonic-assisted soldering could produce the supersaturated dissolution of Mg in the liquid Sn and lead to the existence of two forms of Mg in Sn after solidification. Moreover, the formation and growth of the high-density whiskers were facilitated by the specific contributions of both of the Mg forms in the solid Sn. Specifically, interstitial Mg can provide the persistent driving force for Sn whisker growth, whereas the Mg2Sn phase can increase the formation probability of Sn whiskers. In addition, we presented that the formation and growth of Sn whiskers in the Sn-based solders can be significantly restricted by a small amount of Zn addition (≥3 wt.%), and the prevention mechanisms are attributed to the segregation of Zn atoms at grain or phase boundaries and the formation of the lamellar-type Zn-rich structures in the solder.

Decomposition of Ag-based soldering alloys used in space maintainers after intra-oral exposure. A retrieval analysis study.

PubMed

Soteriou, Despo; Ntasi, Argyro; Papagiannoulis, Lisa; Eliades, Theodore; Zinelis, Spiros

2014-02-01

The aim of this study was to evaluate the elemental alterations of Ag soldering alloys used in space maintainers after intra-oral exposure. Twenty devices were fabricated by using two different soldering alloys; US (Dentaurum Universal Silver Solder, n = 10) and OS (Leone Orthodontic Solder, n = 10). All devices were manufactured by the same technician. Surface morphology and elemental quantitative analysis of the soldering alloys before and after intra-oral placement in patients was determined by scanning electron microscopy and energy-dispersive X-ray microanalysis (SEM/EDX). Statistical analysis was performed by t-test, Mann Whitney tests and Pearson's correlation. For all tests a 95% confidence level was used (α = 0.05). Both soldering alloys demonstrated substantially increase in surface roughness after intra-oral aging. Statistical analysis illustrated a significant decrease in the Cu and Zn content after treatment. OS demonstrated higher Cu release than US (p < 0.05). The remaining relative concentrations of Cu and Zn after the treatment did not show any correlation (p > 0.05) with intra-oral exposure time, apart from Zn in OS (r = 0.840, p = 0.04). Both soldering alloys demonstrated a significant Cu and Zn reduction after intra-oral exposure that may raise biocompatibility concerns.

Low temperature electrical properties of some Pb-free solders

NASA Astrophysics Data System (ADS)

Kisiel, Ryszard; Pekala, Marek

2006-03-01

The electronic industry is engaged in developing Pb-free technologies for more than ten years. However till now not all properties of new solders are described. The aim of the paper is to present some electrical properties of new series of Pb-free solders (eutectic SnAg, near eutectic SnAgCu with and without Bi) in low temperature ranges 10 K to 273K. The following parameters were analyzed: electrical resistivity, temperature coefficient of resistance and thermoelectric power. The electrical resistivity at temperatures above 50 K is a monotonically rising function of temperature for Pb-free solders studied. The electrical resistivity of the Bi containing alloys is higher as compared to the remaining ones. The thermoelectric power values at room temperature are about -8 μV/K to -6 μV/K for Pb-free solders studied, being higher as compared to typical values -3 μVK of SnPb solder. The relatively low absolute values as well as the smooth and weak temperature variation of electrical resistivity in lead free solders enable the possible low temperature application. The moderate values of thermoelectric power around and above the room temperature show that when applying the solders studied the temperature should be kept as uniform as possible, in order to avoid spurious or noise voltages.

The failure models of Sn-based solder joints under coupling effects of electromigration and thermal cycling

NASA Astrophysics Data System (ADS)

Ma, Limin; Zuo, Yong; Liu, Sihan; Guo, Fu; Wang, Xitao

2013-01-01

Currently, the main concerns of Pb-free solder joints are focusing on electromigration (EM) and thermomechanical fatigue (TMF) problems. Many models have been established to understand the failure mechanisms of the joint under such single test conditions. Based on the fact that almost all microelectronic devices serve in combination conditions of fluctuated temperature and electric current stressing, the coupling effects of EM and TMF on evolution of microstructure and resistance of solder joint had been investigated. The failure models of binary SnBi alloy and ternary SnAgCu (SAC) solder under the coupling stressing were divided into four and three different stages, respectively. The failure mechanisms were dominant by the relationship of phase segregation, polarity effect, phase coarsening, and the coefficient of thermal expansion mismatch. Cracks tend to form and propagate along the interface between intermetallic compound layers and solder matrix in SAC solder. However, grain boundary was considered as the nucleation sites for microcracks in SnBi solder. High current density alleviates the deterioration of solder at the beginning stage of coupling stressing through Joule heating effect. An abrupt jump of resistance could be observed before the failure of the joint. The failure molds were determined by interactions of EM behaviors and TMF damages.

Lead-Free Electronics: Impact for Space Electronics

NASA Technical Reports Server (NTRS)

Sampson, Michael J.

2010-01-01

Pb is used as a constituent in solder alloys used to connect and attach electronic parts to printed wiring boards (PWBs). Similar Pbbearing alloys are electroplated or hot dipped onto the terminations of electronic parts to protect the terminations and make them solderable. Changing to Pb-free solders and termination finishes has introduced significant technical challenges into the supply chain. Tin/lead (Sn/Pb) alloys have been the solders of choice for electronics for more than 50 years. Pb-free solder alloys are available but there is not a plug-in replacement for 60/40 or 63/37 (Sn/Pb) alloys, which have been the industry workhorses.

Working with Consortia - Advanced Packaging Reliability

NASA Technical Reports Server (NTRS)

Blanche, Jim; Strickland, Mark

2010-01-01

Description: Support the responsible NASA official for lead-free solder evaluation. Serve as the NASA technical liaison to the NASA/DoD Pb-free Project. Assure NASA areas of interest are included in JG-PP follow-on work. Support NASA/DoD telcons and face-to-face meetings. Update MSFC lead-free solder lessons learned report. FY10 plans: - Reliability data on lead-free solder applications for various part lead finishes and board finishes. - Update lead-free solder risks and risk mitigation strategies for NASA. - Evaluate lead-free alloy/lead-free finish reliability in design application. - Status CAVE project on Pb-free solder aging effects. - Compile the LTESE flight and bench data.

Multiwire conductor having greatly increased interwire resistance and method for making same

DOEpatents

Luhman, Thomas; Suenaga, Masaki

1984-01-17

An improved multiwire conductor of the type which is mechanically stabilized by a tin based solder filler. A solder filled conductor is heated to a temperature above its melting point for a period long enough to allow a substantial amount of copper to be dissolved from the wires comprising the conductor. The copper forms the brittle intermetallic compound Cu.sub.5 Sn.sub.6 with tin in the solder. After cooling the conductor is flexed causing a random cracking of the solder, and thereby increasing the interwire resistance of the conductor. The subject invention is particularly adapted for use with braided, ribbon-type solder filled superconductors.

Thermal Testing and Quality Assurance of BGA LCC & QFN Electronic Packages

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kuper, Cameron Mathias

The purpose of this project is to experimentally validate the thermal fatigue life of solder interconnects for a variety of surface mount electronic packages. Over the years, there has been a significant amount of research and analysis in the fracture of solder joints on printed circuit boards. Solder is important in the mechanical and electronic functionality of the component. It is important throughout the life of the product that the solder remains crack and fracture free. The specific type of solder used in this experiment is a 63Sn37Pb eutectic alloy. Each package was surrounded conformal coating or underfill material.

Alignment-enhancing feed-through conductors for stackable silicon-on-sapphire wafers

NASA Technical Reports Server (NTRS)

Anthony, Thomas R. (Inventor)

1983-01-01

Alignment-enhancing electrically conductive feed-through paths are provided for the high-speed low-loss transfer of electrical signals between integrated circuits of a plurality of silicon-on-sapphire bodies arrayed in a stack. The alignment-enhancing feed-throughs are made by a process involving the drilling of holes through the body, double-sided sputtering, electroplating, and the filling of the holes with solder by capillary action. The alignment-enhancing feed-throughs are activated by forming a stack of wafers and remelting the solder whereupon the wafers, and the feed-through paths, are pulled into alignment by surface tension forces.

The NASA welding assessment program

NASA Technical Reports Server (NTRS)

Scott-Monck, J.; Bozek, J.

1984-01-01

The potential cost and performance advantages of welding was understood but ignored by solar panel manufacturers in the U.S. Although NASA, DOD and COMSAT have supported welding development efforts, soldering remains the only U.S. space qualified method for interconnecting solar cells. The reason is that no U.S. satellite prime contractor found it necessary, due to mission requirements, to abandon the space proven soldering process. It appears that the proposed NASA space station program will provide an array requirement, a 10 year operation in a low Earth orbital environment, that mandates welding. The status of welding technology in the U.S. is assessed.

Insert sleeve prevents tube soldering contamination

NASA Technical Reports Server (NTRS)

Stein, J.

1966-01-01

Teflon sleeve insert prevents contamination of internal tube surfaces by solder compound during soldering operations that connect and seal the tube ends. The sleeve insert is pressed into the mating tube ends with a slight interference fit.

Electromigration Failure Mechanism in Sn-Cu Solder Alloys with OSP Cu Surface Finish

NASA Astrophysics Data System (ADS)

Chu, Ming-Hui; Liang, S. W.; Chen, Chih; Huang, Annie T.

2012-09-01

Organic solderable preservative (OSP) has been adopted as the Cu substrate surface finish in flip-chip solder joints for many years. In this study, the electromigration behavior of lead-free Sn-Cu solder alloys with thin-film under bump metallization and OSP surface finish was investigated. The results showed that severe damage occurred on the substrate side (cathode side), whereas the damage on the chip side (cathode side) was not severe. The damage on the substrate side included void formation, copper dissolution, and formation of intermetallic compounds (IMCs). The OSP Cu interface on the substrate side became the weakest point in the solder joint even when thin-film metallization was used on the chip side. Three-dimensional simulations were employed to investigate the current density distribution in the area between the OSP Cu surface finish and the solder. The results indicated that the current density was higher along the periphery of the bonding area between the solder and the Cu pad, consistent with the area of IMC and void formation in our experimental results.

Influence of Co and W powders on viscosity of composite solders during soldering of specially shaped diamond-abrasive tools

NASA Astrophysics Data System (ADS)

Sokolov, E. G.; Aref’eva, S. A.; Svistun, L. I.

2018-03-01

The influence of Co and W powders on the structure and the viscosity of composite solders Sn-Cu-Co-W used for the manufacture of the specially shaped diamond tools has been studied. The solders were obtained by mixing the metallic powders with an organic binder. The mixtures with and without diamonds were applied to steel rollers and shaped substrates. The sintering was carried out in a vacuum at 820 ° C with time-exposure of 40 minutes. The influence of Co and W powders on the viscosity solders was evaluated on the basis of the study of structures and according to the results of sintering specially shaped diamond tools. It was found that to provide the necessary viscosity and to obtain the uniform diamond-containing layers on the complex shaped surfaces, Sn-Cu-Co-W solder should contain 27–35 vol % of solid phase. This is achieved with a total solder content of 24–32 wt % of cobalt powder and 7 wt % of tungsten powder.

The influence of temperature and humidity on printed wiring board surface finishes: Immersion tin vs organic azoles

NASA Astrophysics Data System (ADS)

Ray, U.; Artaki, I.; Gordon, H. M.; Vianco, P. T.

1994-08-01

Substitution of lead-free solders in electronic assemblies requires changes in the conventional Sn:Pb finishes on substrates and component leads to prevent contamination of the candidate lead-free solder. Options for solderability preservative coatings on the printed wiring board include organic (azole or rosin/resin based) films and tin-based plated metallic coatings. This paper compares the solderability performance and corrosion protection effectiveness of electroless tin coatings vs organic azole films after exposure to a series of humidity and thermal cycling conditions. The solderability of immersion tin is directly related to the tin oxide growth on the surface and is not affected by the formation of SnCu intermetallic phases as long as the intermetallic phase is underneath a protective Sn layer. Thin azole films decompose upon heating in the presence of oxygen and lead to solderability degradation. Evaluations of lead-free solder pastes for surface mount assembly applications indicate that immersion tin significantly improves the spreading of Sn:Ag and Sn:Bi alloys as compared to azole surface finishes.

A maximum entropy fracture model for low and high strain-rate fracture in TinSilverCopper alloys

NASA Astrophysics Data System (ADS)

Chan, Dennis K.

SnAgCu solder alloys exhibit significant rate-dependent constitutive behavior. Solder joints made of these alloys exhibit failure modes that are also rate-dependent. Solder joints are an integral part of microelectronic packages and are subjected to a wide variety of loading conditions which range from thermo-mechanical fatigue to impact loading. Consequently, there is a need for non-empirical rate-dependent failure theory that is able to accurately predict fracture in these solder joints. In the present thesis, various failure models are first reviewed. But, these models are typically empirical or are not valid for solder joints due to limiting assumptions such as elastic behavior. Here, the development and validation of a maximum entropy fracture model (MEFM) valid for low strain-rate fracture in SnAgCu solders is presented. To this end, work on characterizing SnAgCu solder behavior at low strain-rates using a specially designed tester to estimate parameters for constitutive models is presented. Next, the maximum entropy fracture model is reviewed. This failure model uses a single damage accumulation parameter and relates the risk of fracture to accumulated inelastic dissipation. A methodology is presented to extract this model parameter through a custom-built microscale mechanical tester for Sn3.8Ag0.7Cu solder. This single parameter is used to numerically simulate fracture in two solder joints with entirely different geometries. The simulations are compared to experimentally observed fracture in these same packages. Following the simulations of fracture at low strain rate, the constitutive behavior of solder alloys across nine decades of strain rates through MTS compression tests and split-Hopkinson bar are presented. Preliminary work on using orthogonal machining as novel technique of material characterization at high strain rates is also presented. The resultant data from the MTS compression and split-Hopkinson bar tester is used to demonstrate the localization of stress to the interface of solder joints at high strain rates. The MEFM is further extended to predict failure in brittle materials. Such an extension allows for fracture prediction within intermetallic compounds (IMCs) in solder joints. It has been experimentally observed that the failure mode shifts from bulk solder to the IMC layer with increasing loading rates. The extension of the MEFM would allow for prediction of the fracture mode within the solder joint under different loading conditions. A fracture model capable of predicting failure modes at higher strain rates is necessary, as mobile electronics are becoming ubiquitous. Mobile devices are prone to being dropped which can induce loading rates within solder joints that are much larger than experienced under thermo-mechanical fatigue. A range of possible damage accumulation parameters for Cu6Sn 5 is determined for the MEFM. A value within the aforementioned range is used to demonstrate the increasing likelihood of IMC fracture in solder joints with larger loading rates. The thesis is concluded with remarks about ongoing work that include determining a more accurate damage accumulation parameter for Cu6Sn 5 IMC, and on using machining as a technique for extracting failure parameters for the MEFM.

Solderability test system

DOEpatents

Yost, F.; Hosking, F.M.; Jellison, J.L.; Short, B.; Giversen, T.; Reed, J.R.

1998-10-27

A new test method to quantify capillary flow solderability on a printed wiring board surface finish. The test is based on solder flow from a pad onto narrow strips or lines. A test procedure and video image analysis technique were developed for conducting the test and evaluating the data. Feasibility tests revealed that the wetted distance was sensitive to the ratio of pad radius to line width (l/r), solder volume, and flux predry time. 11 figs.

Solder Creep-Fatigue Interactions with Flexible Leaded Part

NASA Technical Reports Server (NTRS)

Ross, R. G., Jr.; Wen, L. C.

1994-01-01

In most electronic packaging applications it is not a single high stress event that breaks a component solder joint; rather it is repeated or prolonged load applications that result in fatigue or creep failure of the solder. The principal strain in solder joints is caused by differential expansion between the part and its mounting environment due to hanges in temperature (thermal cycles) and/or due to temperature gradients between the part and the board.

Tin soldering of aluminum and its alloys

NASA Technical Reports Server (NTRS)

Gallo, Gino

1921-01-01

A method is presented for soldering aluminum to other metals. The method adopted consists of a galvanic application to the surface of the light-metal parts to be soldered, of a layer of another metal, which, without reacting electrolytically on the aluminum, adheres strongly to the surface to which it is applied, and is, on the other hand, adapted to receive the soft solder. The metal found to meet the criteria best was iron.

Electromigration induced high fraction of compound formation in SnAgCu flip chip solder joints with copper column

NASA Astrophysics Data System (ADS)

Xu, Luhua; Han, Jung-Kyu; Liang, Jarrett Jun; Tu, K. N.; Lai, Yi-Shao

2008-06-01

To overcome the effect of current crowding on electromigration-induced pancake-type void formation in flip chip solder joints, two types of Cu column in 90μm flip chip SnAgCu solder joints have been studied. They were (1) the solder contacts the Cu column at bottom and side walls and (2) the solder wets only the bottom surface of the copper column. With a current density of 1.6×104A/cm2 at 135°C, no failure was detected after 1290h. However, the resistance increased by about 10% due to the formation of a large fraction of intermetallic compounds. We found that electromigration has accelerated the consumption rate of copper column and converted almost the entire solder joint into intermetallic compound. Mechanically, drop impact test indicates a brittle fracture failure in the intermetallic. The electromigration critical product for the intermetallic is discussed.

Soldering mask laser removal from printed circuit boards aiming copper recycling.

PubMed

Raele, Marcus Paulo; De Pretto, Lucas Ramos; Zezell, Denise Maria

2017-10-01

Management of waste of electric and electronic equipment (WEEE) is a key issue for modern societies; furthermore, it contains valuable materials that can be recycled, especially in printed circuit boards (PCB), which have approximately one-third of their weight in copper. In this study we demonstrated the use of laser to strip the covering soldering mask on PCB's, thus exposing the copper underneath so that extraction techniques may take place. Using a Q-Switched Nd:YAG laser operating at 1064nm and 532nm we tested the procedure under different energy conditions. The laser stripping of the soldering mask was achieved with satisfactory results by irradiation with 225mJ at 1064nm. However, when using similar parameters at 532nm the process of the coating ejection was not promoted properly, leading to a faulty detachment. Infrared laser PCB stripping presents itself to be technically viable and environmental friendly, since it uses no chemicals inputs, offering one more option to WEEE treatment and recycling. Copyright © 2017 Elsevier Ltd. All rights reserved.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rejent, J.A.; Vianco, P.T.; Woodrum, R.A.

Aging analyses were performed on solder joints from two radar units: (1) a laboratory, N57 tube-type radar unit and (2) a field-returned, B61-0, tube-type radar unit. The cumulative temperature environments experienced by the units during aging were calculated from the intermetallic compound layer thickness and the mean Pb-rich phase particle size metrics for solder joints in the units, assuming an aging time of 35 years for both radars. Baseline aging metrics were obtained from a laboratory test vehicle assembled at AS/FM and T; the aging kinetics of both metrics were calculated from isothermal aging experiments. The N57 radar unit interconnectmore » board solder joints exhibited very little aging. The eyelet solder joints did show cracking that most likely occurred at the time of assembly. The eyelet, SA1126 connector solder joints, showed some delamination between the Cu pad and underlying laminate. The B61 field-returned radar solder joints showed a nominal degree of aging. Cracking of the eyelet solder joints was observed. The Pb-rich phase particle measurements indicated additional aging of the interconnects as a result of residual stresses. Cracking of the terminal pole connector, pin-to-pin solder joint was observed; but it was not believed to jeopardize the electrical functionality of the interconnect. Extending the stockpile lifetime of the B61 tube-type radar by an additional 20 years would not be impacted by the reliability of the solder joints with respect to further growth of the intermetallic compound layer. Additional coarsening of the Pb-rich phase will increase the joints' sensitivity to thermomechanical fatigue.« less

Electromigration Critical Product to Measure Effect of Underfill Material in Suppressing Bi Segregation in Sn-58Bi Solder

NASA Astrophysics Data System (ADS)

Zhao, Xu; Takaya, Satoshi; Muraoka, Mikio

2017-08-01

Recently, we detected length-dependent electromigration (EM) behavior in Sn-58Bi (SB) solder and revealed the existence of Bi back-flow, which retards EM-induced Bi segregation and is dependent on solder length. The cause of the back-flow is attributed to an oxide layer formed on the SB solder. At present, underfill (UF) material is commonly used in flip-chip packaging as filler between chip and substrate to surround solder bumps. In this study, we quantitatively investigated the effect of UF material as a passivation layer on EM in SB solder strips. EM tests on SB solder strips with length of 50 μm, 100 μm, and 150 μm were conducted simultaneously. Some samples were coated with commercial thermosetting epoxy UF material, which acted as a passivation layer on the Cu-SB-Cu interconnections. The value of the critical product for SB solder was estimated to be 38 A/cm to 43 A/cm at 353 K to 373 K without UF coating and 59 A/cm at 373 K with UF coating. The UF material acting as a passivation layer suppressed EM-induced Bi segregation and increased the threshold current density by 37% to 55%. However, at very high current density, this effect became very slight. In addition, Bi atoms can diffuse to the anode side through the Sn phase, hence addition of microelements to the Sn phase to form obstacles, such as intermetallic compounds, may retard Bi segregation in SB solder.

Joint Lead-Free Solder Test Program for High Reliability Military and Space Applications

NASA Technical Reports Server (NTRS)

Brown, Christina

2004-01-01

Current and future space and defense systems face potential risks from the continued use of tin-lead solder, including: compliance with current environmental regulations, concerns about potential environmental legislation banning lead-containing products, reduced mission readiness, and component obsolescence with lead surface finishes. For example, the United States Environmental Protection Agency (USEPA) has lowered the Toxic Chemical Release reporting threshold for lead to 100 pounds. Overseas, the Waste Electrical and Electronic Equipment (WEEE) and the Restriction on Hazardous Substances (RoHS) Dicctives in Europe and similar mandates in Japan have instilled concern that a legislative body will prohibit the use of lead in aerospace/military electronics soldering. Any potential banning of lead compounds could reduce the supplier base and adversely affect the readiness of missions led by the National Aeronautics and Space Administration (NASA) and the U.S. Department of Defense (DoD). Before considering lead-free electronics for system upgrades or future designs, however, it is important for the DoD and NASA to know whether lead-free solders can meet their systems' requirements. No single lead-free solder is likely to qualify for all defense and space applications. Therefore, it is important to validate alternative solders for discrete applications. As a result of the need for comprehensive test data on the reliability of lead-free solders, a partnership was formed between the DoD, NASA, and several original equipment manufactures (OEMs) to conduct solder-joint reliability (laboratory) testing of three lead-free solder alloys on newly manufactured and reworked circuit cards to generate performance data for high-reliability (IPC Class 3) applications.

Albumin solder covalently bound to a polymer membrane: New approach to improve binding strength in laser tissue soldering in-vitro.

PubMed

Hiebl, B; Ascher, L; Luetzow, K; Kratz, K; Gruber, C; Mrowietz, C; Nehring, M E; Lendlein, A; Franke, R-P; Jung, F

2018-01-01

Laser tissue soldering (LTS) based on indocyanine green (ICG)-mediated heat-denaturation of proteins might be a promising alternative technique for micro-suturing, but up to now the problem of too weak shear strength of the solder welds in comparison to sutures is not solved. Earlier reports gave promising results showing that solder supported by carrier materials can enhance the cohesive strength of the liquid solder. In these studies, the solder was applied to the carriers by dip coating. Higher reliability of the connection between the solder and the carrier material is expected when the solder is bound covalently to the carrier material. In the present study a poly(ether imide) (PEI) membrane served as carrier material and ICG-supplemented albumin as solder substrate. The latter was covalently coupled to the carrier membrane under physiological conditions to prevent structural protein changes. As laser source a diode continuous-wave laser emitting at 808 nm with intensities between 250 mW and 1500 mW was utilized. The albumin functionalized carrier membrane was placed onto the tunica media of explanted pig thoracic aortae forming an overlapping area of approximately 0.5×0.5 cm2. All tests were performed in a dry state to prevent laser light absorption by water. Infrared spectroscopy, spectro-photometrical determination of the secondary and primary amine groups after acid orange II staining, contact angle measurements, and atomic force microscopy proved the successful functionalization of the PEI membrane with albumin. A laser power of 450 mW LTS could generate a membrane-blood vessel connection which was characterized by a shear strength of 0.08±0.002 MPa, corresponding to 15% of the tensile strength of the native blood vessel. Theoretically, an overlapping zone of 4.1 mm around the entire circumference of the blood vessel could have provided shear strength of the PEI membrane-blood vessel compound identical to the tensile strength of the native blood vessel. These in-vitro results confirmed the beneficial effects of solder reinforcement by carrier membranes, and suggest LTS with covalently bound solders on PEI substrates for further studies in animal models.

The mechanism of exogenous adiponectin in the prevention of no-reflow phenomenon in type 2 diabetic patients with acute myocardial infarction during PCI treatment.

PubMed

Zhang, C-J; Deng, Y-Z; Lei, Y-H; Zhao, J-B; Wei, W; Li, Y-H

2018-04-01

To investigate the mechanism of exogenous adiponectin in the prevention of no-reflow phenomenon in type 2 diabetic (T2DM) patients with acute myocardial infarction (AMI) during percutaneous coronary intervention (PCI) treatment. 66 patients were randomly divided into control group and observation group, 33 cases in each group. According to the percutaneous coronary intervention (PCI) emergency treatment principle, patients from the control group were treated with an intracoronary injection of adenosine combined with a micro-pump intravenous infusion of tirofiban. Patients from the observation group were injected with exogenous adiponectin in addition to the adenosine and tirofiban treatments. There were no significant differences in gender, age, location of the target lesion, degree of stenosis, stent implantation number, length and the inner diameter between control and observation group (p > 0.05). Lower frequent of slow blood flow and no-reflow and shorter interventional procedures were observed in observation group compared with those of control group (p < 0.05). Moreover, the increase of plasma creatine kinase (CK-MB) in patients of observation group was lower than that of the patients in control group (p < 0.05). In addition, the levels of troponin-I (cTnI), IL-6, TNF- α, endothelin-1 (ET-1), vascular endothelial adhesion molecular I (VCAM-1) and bax/Bcl-2 were significantly lower in observation group than those in control (p < 0.05). Furthermore, the occurrence of major adverse cardiac events (MACE) during a 12-month follow-up was significantly lower in the observation group than that of control (p < 0.05). Exogenous adiponectin further reduced the no-reflow phenomenon during PCI treatment of the patients with T2DM combined with AMI. The function of exogenous adiponectin is associated with the reduced myocardial and endothelial cell injury and the inhibited inflammation and apoptosis. The application of exogenous adiponectin can significantly improve the clinical outcomes.

Prediction of the filter no-reflow phenomenon in patients with angina pectoris by using multimodality: Magnetic resonance imaging, optical coherence tomography, and serum biomarkers.

PubMed

Matsumoto, Kenji; Ehara, Shoichi; Hasegawa, Takao; Otsuka, Kenichiro; Yoshikawa, Junichi; Shimada, Kenei

2016-05-01

Although the occurrence of no-reflow during percutaneous coronary intervention (PCI) has been shown to be associated with worse short- and long-term clinical outcomes, the clinical relevance of preventing flow deterioration by using the filter-based distal protection devices (DPDs) is controversial. We investigated predictors of the filter no-reflow (FNR) phenomenon during PCI by using multimodality, such as hyperintense plaques (HIPs) in the coronary artery on T1-weighted imaging (T1WI) non-contrast magnetic resonance, plaque composition by using optical coherence tomography (OCT), and serum biomarkers, in patients with angina pectoris. Fifty lesions from 50 patients with angina were examined. All patients underwent T1WI within 24 h before invasive coronary angiography was performed, and preinterventional OCT was performed on a native atherosclerotic culprit lesion. The signal intensity of coronary plaque to cardiac muscle ratio (PMR) was calculated on a standard console of the magnetic resonance system. Of the 50 lesions, 20 lesions showed FNR during PCI, while non-FNR was observed in 30 lesions. A cut-off value >1.85 of PMR had a sensitivity of 65%, a specificity of 93%, a positive predictive value of 87%, and a negative predictive value of 80% for identifying lesions with FNR. Multivariate analysis revealed that the presence of HIPs with PMR >1.85 (p=0.008) was the only independent predictor of the FNR phenomenon during PCI. This study shows that the presence of HIPs with PMR >1.85 on T1WI was a novel independent predictor of the FNR phenomenon during PCI in angina patients. This result may help in identifying high-risk lesions for no-reflow to deploy filter-based DPDs. Copyright © 2015 Japanese College of Cardiology. Published by Elsevier Ltd. All rights reserved.

Multiwire conductor having greatly increased interwire resistance and method for making same

DOEpatents

Luhman, T.; Suenaga, M.

1982-03-15

An improved multiwire conductor of the type which is mechanically stabilized by a tin based solder filler is described. A solder filled conductor is heated to a temperature above its melting point for a period long enough to allow a substantial amount of copper to be dissolved from the wires comprising the conductor. The copper forms the brittle intermetallic compound Cu/sub 5/Sn/sub 6/ with tin in the solder. After cooling the conductor is flexed causing a random cracking of the solder, and thereby increasing the interwire resistance of the conductor. The subject invention is particularly adapted for use with braided, ribbon-type solder filled superconductors.

Induction soldering of photovoltaic system components

DOEpatents

Kumaria, Shashwat; de Leon, Briccio

2015-11-17

A method comprises positioning a pair of photovoltaic wafers in a side-by-side arrangement. An interconnect is placed on the pair of wafers such that the interconnect overlaps both wafers of the pair, solder material being provided between the interconnect and the respective wafers. A solder head is then located adjacent the interconnect, and the coil is energized to effect inductive heating of the solder material. The solder head comprises an induction coil shaped to define an eye, and a magnetic field concentrator located at least partially in the eye of the coil. The magnetic field concentrator defines a passage extending axially through the eye of the coil, and may be of a material with a high magnetic permeability.

Accelerated Metastable Solid-liquid Interdiffusion Bonding with High Thermal Stability and Power Handling

NASA Astrophysics Data System (ADS)

Huang, Ting-Chia; Smet, Vanessa; Kawamoto, Satomi; Pulugurtha, Markondeya R.; Tummala, Rao R.

2018-01-01

Emerging high-performance systems are driving the need for advanced packaging solutions such as 3-D integrated circuits (ICs) and 2.5-D system integration with increasing performance and reliability requirements for off-chip interconnections. Solid-liquid interdiffusion (SLID) bonding resulting in all-intermetallic joints has been proposed to extend the applicability of solders, but faces fundamental and manufacturing challenges hindering its wide adoption. This paper introduces a Cu-Sn SLID interconnection technology, aiming at stabilization of the microstructure in the Cu6Sn5 metastable phase rather than the usual stable Cu3Sn phase. This enables formation of a void-free interface yielding higher mechanical strength than standard SLID bonding, as well as significantly reducing the transition time. The metastable SLID technology retains the benefits of standard SLID with superior I/O pitch scalability, thermal stability and current handling capability, while advancing assembly manufacturability. In the proposed concept, the interfacial reaction is controlled by introducing Ni(P) diffusion barrier layers, designed to effectively isolate the metastable Cu6Sn5 phase preventing any further transformation. Theoretical diffusion and kinetic models were applied to design the Ni-Cu-Sn interconnection stack to achieve the targeted joint composition. A daisy chain test vehicle was used to demonstrate this technology as a first proof of concept. Full transition to Cu6Sn5 was successfully achieved within a minute at 260°C as confirmed by scanning electron microscope (SEM) and x-ray energy dispersive spectroscopy (XEDS) analysis. The joint composition was stable through 10× reflow, with outstanding bond strength averaging 90 MPa. The metastable SLID interconnections also showed excellent electromigration performance, surviving 500 h of current stressing at 105 A/cm2 at 150°C.

Preliminary biocompatibility experiment of polymer films for laser-assisted tissue welding.

PubMed

Sorg, Brian S; Welch, Ashley J

2003-01-01

The purpose of this study was to examine the impact of a polymer film for liquid solder strength reinforcement on the short term healing of a wound closed by laser-tissue soldering. Full thickness incisions created on the dorsum of Sprague-Dawley rats were closed by laser-tissue soldering: albumin solder with Indocyanine Green (ICG) dye was inserted between the incision edges and photothermally coagulated with a diode laser. A poly(DL-lactic-co-glycolic acid) (PLGA) polymer film was implanted subcutaneously in the bottom of the incision (controls had no film). Specimens were harvested at 0, 3, 7, and 14 days for breaking strength testing and histological analysis. Breaking strengths of the controls at 0 and 14 days were statistically stronger than the specimens with the implanted films (t-test, P < 0.05). A slight difficulty in apposing the wound edges due to the film presence may have contributed to the low acute strengths. Interference with the wound contraction process by the films possibly contributed to the lower breaking strength at 14 days. Wound histology indicated a mild foreign body reaction to the polymer film material. The polymer film was well tolerated by the tissue, and the tissue response to the material was consistent with that seen in the literature. The breaking strength differences between control and film-implanted specimens at 0 and 14 days were probably the result of mechanical complications (tissue apposition and wound contraction) due to the presence of the film, and not due to the film material itself. The use of polymer film patches for liquid solder reinforcement and breaking strength enhancement may have certain application specific issues that need to be addressed. Strategies to account for these issues require further research. Copyright 2003 Wiley-Liss, Inc.

The Failure Models of Lead Free Sn-3.0Ag-0.5Cu Solder Joint Reliability Under Low-G and High-G Drop Impact

NASA Astrophysics Data System (ADS)

Gu, Jian; Lei, YongPing; Lin, Jian; Fu, HanGuang; Wu, Zhongwei

2017-02-01

The reliability of Sn-3.0Ag-0.5Cu (SAC 305) solder joint under a broad level of drop impacts was studied. The failure performance of solder joint, failure probability and failure position were analyzed under two shock test conditions, i.e., 1000 g for 1 ms and 300 g for 2 ms. The stress distribution on the solder joint was calculated by ABAQUS. The results revealed that the dominant reason was the tension due to the difference in stiffness between the print circuit board and ball grid array, and the maximum tension of 121.1 MPa and 31.1 MPa, respectively, under both 1000 g or 300 g drop impact, was focused on the corner of the solder joint which was located in the outmost corner of the solder ball row. The failure modes were summarized into the following four modes: initiation and propagation through the (1) intermetallic compound layer, (2) Ni layer, (3) Cu pad, or (4) Sn-matrix. The outmost corner of the solder ball row had a high failure probability under both 1000 g and 300 g drop impact. The number of failures of solder ball under the 300 g drop impact was higher than that under the 1000 g drop impact. The characteristic drop values for failure were 41 and 15,199, respectively, following the statistics.

Fast formation and growth of high-density Sn whiskers in Mg/Sn-based solder/Mg joints by ultrasonic-assisted soldering: Phenomena, mechanism and prevention

PubMed Central

Li, M. Y.; Yang, H. F.; Zhang, Z. H.; Gu, J. H.; Yang, S. H.

2016-01-01

A universally applicable method for promoting the fast formation and growth of high-density Sn whiskers on solders was developed by fabricating Mg/Sn-based solder/Mg joints using ultrasonic-assisted soldering at 250 °C for 6 s and then subjected to thermal aging at 25 °C for 7 d. The results showed that the use of the ultrasonic-assisted soldering could produce the supersaturated dissolution of Mg in the liquid Sn and lead to the existence of two forms of Mg in Sn after solidification. Moreover, the formation and growth of the high-density whiskers were facilitated by the specific contributions of both of the Mg forms in the solid Sn. Specifically, interstitial Mg can provide the persistent driving force for Sn whisker growth, whereas the Mg2Sn phase can increase the formation probability of Sn whiskers. In addition, we presented that the formation and growth of Sn whiskers in the Sn-based solders can be significantly restricted by a small amount of Zn addition (≥3 wt.%), and the prevention mechanisms are attributed to the segregation of Zn atoms at grain or phase boundaries and the formation of the lamellar-type Zn-rich structures in the solder. PMID:27273421

From cells to laminate: probing and modeling residual stress evolution in thin silicon photovoltaic modules using synchrotron X-ray micro-diffraction experiments and finite element simulations

DOE PAGES

Tippabhotla, Sasi Kumar; Radchenko, Ihor; Song, W. J. R.; ...

2017-04-12

Fracture of silicon crystalline solar cells has recently been observed in increasing percentages especially in solar photovoltaic (PV) modules involving thinner silicon solar cells (<200 μm). Many failures due to fracture have been reported from the field because of environmental loading (snow, wind, etc.) as well as mishandling of the solar PV modules (during installation, maintenance, etc.). However, a significantly higher number of failures have also been reported during module encapsulation (lamination) indicating high residual stress in the modules and thus more prone to cell cracking. Here in this paper we report through the use of synchrotron X-ray submicron diffractionmore » coupled with physics-based finite element modeling, the complete residual stress evolution in mono-crystalline silicon solar cells during PV module integration process. For the first time, we unravel the reason for the high stress and cracking of silicon cells near soldered inter-connects. Our experiments revealed a significant increase of residual stress in the silicon cell near the solder joint after lamination. Moreover, our finite element simulations show that this increase of stress during lamination is a result of highly localized bending of the cell near the soldered inter-connects. Further, the synchrotron X-ray submicron diffraction has proven to be a very effective way to quantitatively probe mechanical stress in encapsulated silicon solar cells. Thus, this technique has ultimately enabled these findings leading to the enlightening of the role of soldering and encapsulation processes on the cell residual stress. This model can be further used to suggest methodologies that could lead to lower stress in encapsulated silicon solar cells, which are the subjects of our continued investigations.« less

From cells to laminate: probing and modeling residual stress evolution in thin silicon photovoltaic modules using synchrotron X-ray micro-diffraction experiments and finite element simulations

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tippabhotla, Sasi Kumar; Radchenko, Ihor; Song, W. J. R.

Fracture of silicon crystalline solar cells has recently been observed in increasing percentages especially in solar photovoltaic (PV) modules involving thinner silicon solar cells (<200 μm). Many failures due to fracture have been reported from the field because of environmental loading (snow, wind, etc.) as well as mishandling of the solar PV modules (during installation, maintenance, etc.). However, a significantly higher number of failures have also been reported during module encapsulation (lamination) indicating high residual stress in the modules and thus more prone to cell cracking. Here in this paper we report through the use of synchrotron X-ray submicron diffractionmore » coupled with physics-based finite element modeling, the complete residual stress evolution in mono-crystalline silicon solar cells during PV module integration process. For the first time, we unravel the reason for the high stress and cracking of silicon cells near soldered inter-connects. Our experiments revealed a significant increase of residual stress in the silicon cell near the solder joint after lamination. Moreover, our finite element simulations show that this increase of stress during lamination is a result of highly localized bending of the cell near the soldered inter-connects. Further, the synchrotron X-ray submicron diffraction has proven to be a very effective way to quantitatively probe mechanical stress in encapsulated silicon solar cells. Thus, this technique has ultimately enabled these findings leading to the enlightening of the role of soldering and encapsulation processes on the cell residual stress. This model can be further used to suggest methodologies that could lead to lower stress in encapsulated silicon solar cells, which are the subjects of our continued investigations.« less

Equilibrative nucleoside transporter 1 (ENT1) regulates postischemic blood flow during acute kidney injury in mice

PubMed Central

Grenz, Almut; Bauerle, Jessica D.; Dalton, Julee H.; Ridyard, Douglas; Badulak, Alexander; Tak, Eunyoung; McNamee, Eóin N.; Clambey, Eric; Moldovan, Radu; Reyes, German; Klawitter, Jost; Ambler, Kelly; Magee, Kristann; Christians, Uwe; Brodsky, Kelley S.; Ravid, Katya; Choi, Doo-Sup; Wen, Jiaming; Lukashev, Dmitriy; Blackburn, Michael R.; Osswald, Hartmut; Coe, Imogen R.; Nürnberg, Bernd; Haase, Volker H.; Xia, Yang; Sitkovsky, Michail; Eltzschig, Holger K.

2012-01-01

A complex biologic network regulates kidney perfusion under physiologic conditions. This system is profoundly perturbed following renal ischemia, a leading cause of acute kidney injury (AKI) — a life-threatening condition that frequently complicates the care of hospitalized patients. Therapeutic approaches to prevent and treat AKI are extremely limited. Better understanding of the molecular pathways promoting postischemic reflow could provide new candidate targets for AKI therapeutics. Due to its role in adapting tissues to hypoxia, we hypothesized that extracellular adenosine has a regulatory function in the postischemic control of renal perfusion. Consistent with the notion that equilibrative nucleoside transporters (ENTs) terminate adenosine signaling, we observed that pharmacologic ENT inhibition in mice elevated renal adenosine levels and dampened AKI. Deletion of the ENTs resulted in selective protection in Ent1–/– mice. Comprehensive examination of adenosine receptor–knockout mice exposed to AKI demonstrated that renal protection by ENT inhibitors involves the A2B adenosine receptor. Indeed, crosstalk between renal Ent1 and Adora2b expressed on vascular endothelia effectively prevented a postischemic no-reflow phenomenon. These studies identify ENT1 and adenosine receptors as key to the process of reestablishing renal perfusion following ischemic AKI. If translatable from mice to humans, these data have important therapeutic implications. PMID:22269324

A non-contact measurement technique at the micro scale

NASA Astrophysics Data System (ADS)

Ghosh, Santaneel

During their production and normal use, electronic packages experience large temperature excursions, leading to high thermo-mechanical stress gradients that cause fatigue failure of the solder joints. In order to prevent premature failure and prolong the fatigue life of solder joints, there is a pressing need for the characterization of the solder, especially lead-free solder, at the micro-level (joint size). The characterization and modeling of solder behavior at the appropriate scale is a major issue. However, direct measurement techniques are not applicable to characterize the deformation response of solder joints because of their micro scale dimensions. Therefore, a non-contact measurement technique utilizing a Scanning Electron Microscope (SEM) in conjunction with Digital Image Correlation (DIC) has been developed. Validation was achieved by performing a four-point bending test in both an in-house optical system with DIC and inside the SEM. This non-contact measurement technique was then used to extract the stress-strain response of the solder. Mechanical tests were performed on solder joints that were created using the same type of solder balls used in the electronic industry and were representative of normal joint scales. The SEM-DIC technique has been proven to be applicable for the determining the stress-strain response of solder material at the micro-scale. This study resulted in a validated material characterization technique specifically designed for micro-scale material response. One of the main contributions of this study is that the method is a lot simpler and cheaper, yet highly effective, compared to the previous methods. This technique is also readily applicable to the measurement of the stress-strain response of any micro-scale specimen, such as other metals, polymers, etc. Also, the measured displacement field by obtained by DIC can be used as the base for calculating the strain field on the surface of a specimen.

Laser-tissue soldering with biodegradable polymer films in vitro: film surface morphology and hydration effects.

PubMed

Sorg, B S; Welch, A J

2001-01-01

Previous research introduced the concept of using biodegradable polymer film reinforcement of a liquid albumin solder for improvement of the tensile strength of repaired incisions in vitro. In this study, the effect of creating small pores in the PLGA films on the weld breaking strength is studied. Additionally, the effect of hydration on the strength of the reinforced welds is investigated. A 50%(w/v) bovine serum albumin solder with 0.5 mg/mL Indocyanine Green dye was used to repair an incision in bovine aorta. The solder was coagulated with an 806-nm CW diode laser. A poly(DL-lactic-co-glycolic acid) (PLGA) film was used to reinforce the solder (the controls had solder but no reinforcement). Breaking strengths were measured acutely and after hydration in saline for 1 and 2 days. The data were analyzed by ANOVA (P < 0.05) and multiple comparisons of means were performed using the Newman-Keuls test. The creation of pores in the PLGA films qualitatively improved the film flexibility without having an apparent adverse effect on the breaking strength, while the actual technique of applying the film and solder had more of an effect. The acute maximum average breaking strengths of some of the film reinforced specimens (114.7 g-134.4 g) were significantly higher (P < 0.05) than the acute maximum average breaking strength of the unreinforced control specimens (68.3 g). Film reinforced specimens were shown to have a statistically significantly higher breaking strength than unreinforced controls after 1- and 2-day hydration. Reinforcement of liquid albumin solders in laser-assisted incision repair appears to have advantages over conventional methods that do not reinforce the cohesive strength of the solder in terms of acute breaking strength and after immersion in moist environments for short periods of time. Using a film with the solder applied to one surface only may be advantageous over other techniques.