The effect of electromigration (EM) on Sn(Cu)/Ni/Cu solder joint interfaces under current stressing of 10 4 A/cm 2 at 160°C was studied. In the pure Sn/Ni/Cu case, the interfacial compound layer was mainly the Cu 6Sn 5 compound phase, which suffered serious EM-induced dissolution, eventually resulting in serious Cu-pad consumption. In the Sn-0.7Cu case, a (Cu,Ni) 6Sn 5 interfacial compound layer formed at the joint interface, which showed a strong resistance to EM-induced dissolution. Thus, there was no serious consumption of the Cu pad under current stressing. In the Sn-3.0Cu case, we believe that the massive Cu 6Sn 5 phase in the solder matrix eased possible EM-induced dissolution at the interfacial compound layer due to current stressing.
- Ni/Cu bilayer UBM