Stress analysis of Cu pad/solder interfaces

Interfacial fracturing is the most important failure mode of solder joints. In this paper, interfacial stresses of Cu pad/solder interfaces are evaluated based on the theory of interfacial mechanics and the finite element method. Effects of solder joint shapes and solder materials on the stress intensity are investigated. The results show that Sn37Pb/Cu interface has greater stress intensity than that of Sn3.5Ag/Cu and Sn3.0Ag0.5Cu/Cu interfaces, a fatter solder shape increases the stress intensity. Elastic-plastic deformation and strain rate effects in the solder joints reduce the intensity.