Effects of Grain Orientation on the Electromigration of Cu-Reinforced Composite Solder Joints

Grain orientations are a significant factor under high-density current stressing, but there are few literature reports about the influence of grain orientation on electromigration in composite solder joints. Most research relating to the electromigration behavior of composite solders have been carried out by adding different kinds of reinforced particles in order to relieve the electromigration phenomena, while the impacts of grain orientation on the electromigration have been neglected. In this paper, Sn-3.5Ag composite solder joints reinforced by 2 vol.% Cu were fabricated to investigate the effects of Sn grain orientation on electromigration. The one-dimensional single-grained solder joints were stressed under a constant current density of 10 4 A/cm 2 for different times at room temperature. The samples, of which the c -axis of the Sn grains was nearly parallel to the electron flow direction, exhibited serious electromigration-induced phenomena after current stressing for 528 h. However, electromigration was not observed in the samples where the Sn grains had their c -axis perpendicular to the electron flow direction. Therefore, the grain orientations have a great influence on the electromigration behavior in composite solders and Cu atoms moved faster along the c -axis of the Sn grains than along the a - and b -axes during current stressing.