The Evolution of Micro-Voids in Sn37Pb Solder Joints Under Electromechanical Coupling Loading

In this study, a Sn37Pb solder joint was subjected to mechanical loading (constant 5 N force applied in the vertical direction) for a duration of 400 h in order to investigate the evolution of micro-voids. Under electromechanical loading, micro-voids exhibited growth and subsequent shrinkage. Solder joint resistance initially increased and then decreased. The decrease in void volume and the reduction in solder joint resistance are both attributed to the creep deformation occurring in the vertical direction of the solder joint. Notably, no significant element migration was observed within the solder joints after 400 h of loading. The significant stress gradients within the solder joints result in increased back stress, thus balancing the electromigration stress and completely suppressing element migration.