Decoupling microstructure evolution and electric current stressing on damping capacity of serving Sn58Bi solder

The electronics miniaturization, which increases electric current density, has made electromigration (EM) a crucial reliability issue. To quasi-in situ deeply study how the vibration resistance of the serving Sn58Bi solder varies under long-time electric current stressing (ECS), firstly the Sn58Bi solder was imposed under 8.0 A with different time (0, 120, 360, 720, and 1440 h) to trigger EM-induced microstructure evolution. Then, the EM-treated Sn58Bi solders were used to conduct damping tests under different electric currents (0, 4.0, and 8.0 A). The results show that damping capacities under instantaneous ECS are continuously elevated with increasing current, which is attributed to instantaneous physical interaction between the current and microstructure. Moreover, there is a transition in the damping mechanism from dislocation motion dominatedto phase boundary sliding dominated with increasing temperature. Meanwhile, both the strain-dependent and temperature-dependent damping capacities decreased with prolonged EM treatment time, and the deterioration was significant in the initial stage, but then tended to be mitigated. Additionally, as the microstructure coarsened with increasing EM treatment time, the phase boundary sliding dominated damping capacity decreased continuously, while the dislocation motion dominated damping capacity also decreased. The former phenomenon was attributed to microstructure coarsening inducing lower phase boundary density. The latter phenomenon was due to the elevation effect of phase coarsening being weaker than the deterioration effect of tiny Bi particles within the Sn-rich phase by pinning the dislocation motion.