Study of DC and AC Electromigration Behavior in Eutectic Pb-Sn Solder Joints
In this study, direct current (DC) and alternating current (AC) electromigration experiments were carried out using solder joints with a Cu/eutectic Pb-Sn/Cu joint configuration. During stressing using DC and AC, a fixed current density of 104 A/cm2 was applied to the joints at 150°C. In the joints stressed by DC, electromigration-induced damage occurred, and the corresponding microstructural changes mainly included valley and hillock formation in the solder region, pronounced phase segregation of Pb-rich and Sn-rich domains, asymmetric growth of Cu-Sn intermetallics at the interfaces, and excessive depletion of Cu at the cathode side. In contrast, no significant electromigration was observed after the AC treatments. This was especially true for the treatment with AC frequencies higher than 1 h−1. The dependence of the damage on AC frequency suggests that electromigration in solder joints can be inhibited to a large extent when a proper reverse current is delivered.