Reaction Diffusion in the Au-Cu-Pb-Sn System at Low Temperature
The microstructure of a Cu 3 Au v. Pb-5wt%Sn diffusion couple was examined in the as-dipped and annealed conditions. The as-dipped couple showed no reaction between the solder and the base metal. The couple developed intermediate layers of two intermetallic phases upon annealing for 289 hours at 169°C. These phases were identified as phi and eta’ which are contained in the Au-Cu-Sn ternary system. No phases containing significant amounts of Pb formed, indicating that even at low concentrations in a Pb-Sn solder, Sn is the active chemical specie in the solder for the Au-Cu-Pb-Sn system. The microhardness of the eta’ phase was found to be equal to that of Cu 3 Sn, which forms in the absence of Au in the Cu base metal. However, the the phi phase was harder, and therefore the presence of Au in the base metal may adversely affect the thermal fatigue resistance of the solder joint.
A new Ni-W thin film metallization for solder interconnections and design method of metallization thickness
The demand for reliable thin-film metallization that can be repaired repeatedly by soldering has been increasing because multichip module on ceramic (MCM-C) has become widely used in workstations as well as main frame computers. This kind of metallization is also suitable for use with Pb-free solder with a high Sn content whereas a conventional metallization is consumed quickly by Sn. A Ni-W sputtered metallization satisfying this requirement has been developed by the authors. The reaction between Ni-W and Sn during soldering creates a Sn-Ni-W alloy layer. The diffusion of Sn into Ni-W and the formation of Sn-Ni-W is slower than any other thin-film metallization for solder interconnections ever applied to electronic devices, and this makes multiple solder repairs on a substrate possible. Furthermore, Ni-W is adequate for LSI metallization. Additionally, the film thickness appropriate to given amount of solder can be determined by adding the term for solder height to the frequency factor Do. This is especially important in designing fine connections for electronic devices.
Thermal analysis of AuSn-Pb quasibinary section
AbstractAuSn is a compound that melts congruently and which has been shown by previous work to come into quasibinary eutectic equilibrium with Pb. Because there is some disagreement in the results of previous workers, a redetermination of the AuSn-Pb section has been undertaken before the investigation of the total constitution of the Au-Pb-Sn ternary system.