The influence of microstructure characteristic on the electromigration behaviour of line-type Sn58Bi solder joints

摘要

The electromigration (EM) behaviour in the joint mainly depends on the current density; however, for the limitation of experimental methods, the influence of microstructure characteristic of solder matrix on the magnitude and distribution of current density has long been neglected. In this study, the microstructure evolution of eutectic Sn-Bi alloy was modeled numerically using Monte Carlo Potts approach first, and simulation results are consistent well with experimental observation. Then, finite element models based on microstructural simulation results under current stressing were established and analyzed. Simulation results show that the characteristic of eutectic Sn58Bi alloy has obvious influence on the distribution and magnitude of current densities in Sn58Bi solder joints. Moreover, refining the eutectic microstructure has very limited influence on the average current densities in the solder joints, while it may reduce the maximum current density and improve the electromigration reliability. It is speculated that the coarsening process of eutectic structure under current stressing may may affect the EM behaviour of solder joints.