Influence of microstructure inhomogeneity on the current density and temperature gradient in microscale line-type Sn58Bi solder joints under current stressing

Abstract

Due to the increasing miniaturization of microelectronic packaging, the electromigration (EM) phenomenon generally exists in microscale lead-free solder joints, which is mainly caused by high current stressing. To address the limitation of experimental measurement at a microscale, this study performed a finite element analysis (FEA) based on microstructure simulation and image recognition to characterize the influence of microstructure inhomogeneity on the magnitude and distribution of current density and temperature gradient in microscale line-type Sn58Bi solder joints under current stressing. The simulation results indicate that the microstructure inhomogeneity has a significant influence on the magnitude and distribution of the current density and temperature gradient in Sn58Bi solder joints. Specifically, the current density and the total current-induced Joule heats in the Sn-rich phase are much higher than those in the Bi-rich phase. However, the temperature gradient in the Sn-rich phase is smaller than that in the Bi-rich phase. Moreover, similar results and conclusions can be obtained from both two- and three-dimensional FEA.