Electromigration in Lead-Free Sn3.8Ag0.7Cu Solder Reaction Couple

Electromigration is one of the severe reliability problems in IC progress. In this paper, the electromigration of eutectic Sn3.8Ag0.7Cu solder reaction couples were studied under high temperature (150degC) and high current density (5times10³ A/cm²) in three days. An original design which could reduce the local Joule heating caused by current crowding was produced. Voltage change was also monitored during this experiment. Hillocks and valleys were found at the anode side and cathode side respectively. Unlike aging test, electromigration could promote the formation of intermetallic compound (IMC) at cathode side and inhibit the formation of IMC at anode side. Cracks also appeared along the cathode side after electromigration in three days, but they were not leading the solder reaction couple to failure.