Small-Scale Multiaxial Deformation Experiments on Solder for High-Fidelity Model Development

[摘要] Solder in our applications is used for more than just an electrical connection. It also serves as the load bearing structures for some electronic components. Thus the mechanical properties of solder interconnects were studied to ensure the reliability of electronic assemblies. Studies include deformation and failure associated with size effect, deformation mechanism map, and microstructural coarsening. Results show that tensile stress-strain behavior is size dependent. Small solder specimens do not follow bulk material properties when the cross-sectional area of the gage section is less than 0.1 mm{sup 2}. The effect of microstructural size is found to be minimal, based on two averaged Pb-rich phase sizes, 2 and 4 {micro}m. From multiaxial creep experiments at room temperature and 100 C, the activation energy and stress exponent are consistent with published values for Region-I creep behavior. The creep conditions explored in this study establish the aspects of a multiaxial deformation mechanism map that are typical of normal stockpile conditions. The Von Mises equivalent stress appears to work well for various loading modes. The coarsening phenomenon of eutectic solder is still not very clear. It requires a large number of observations to mitigate the extensive variability in both starting microstructure and response. From isothermal torsional fatigue at 10{sup -4} and 10{sup -5} s{sup -1}, there is no correlation between the initial phase size and the magnitude of accumulated strain experienced by the specimen. In creep specimens, localized coarsening is observed at the failed region for some loading conditions, predominantly under pure shear.

[发布日期] 2002-12-01 [发布机构] Sandia National Laboratories

[关键词] Metallurgical Flux;Mechanical Properties;Eutectics;36 Materials Science;Shear