The effects of creep on electromigration behaviors in Sn-based Pb-free solder joints

Nowadays, the combination effects of thermal, mechanical and electrical on the reliability issues of solder joint gain more and more attentions. The independent failure mechanisms of solder joints are widely investigated and comprehended under single conditions as listed above. However, the coupling effect of thermal, mechanical and electrical needs further exploration. Consequently, the failure behaviors of solder joint under coupling of high current density and creep become a critical problem. The sandwich Cu/Sn3.0Ag0.5Cu/Cu solder joints which subject to constant ambient temperature and creep stress but different current density are systematically investigated in the study. The failure behaviors of solder is analyzed and discussed by observation of the resistance change, microstructure evolution and orientation transition of solder joints. The effects of mechanical, thermal, and electrical on the damage calculation are also illustrated individually. The results indicate that, failure mechanism of solder joint under a constant creep stress of 5.5MPa and low current density was controlled by grain boundary sliding. The damage easily accumulated near both interfaces of solder/Cu. The electromigration process could alleviate creep damage by released grain boundary sliding and changed stress distribution in the solder joint at initial stage.