Effect of Passivation Opening on Electromigration in Eutectic SnPb Solder Joints

Effect of passivation opening on electromigration in eutectic SnPb solder joints is investigated in this study. Solder bumps were fabricated with a polyimide (PI) and without a PI layer. Both sets of solder joints were subjected to electromigration tests by 0.8A at 150 degrees C. Kelvin probes were employed to monitor the increase in bump resistance during electromigration. The bump failure is defined when the bump resistance increase to 100% of its initial value. It is found that the failure time is different for the two joints and the failure occurs in different locations for the two joints. 3D simulation on current density is performed to examine the difference in current distribution for the two joints. It is found that the current density distribution plays key roles in the failure location of electromigration.