Effects of current density and temperature on Sn/Ni interfacial reactions under current stressing

This research studied the electromigration effects on Sn/Ni/Sn sandwich-type couple interfacial reactions with various electric current densities at different temperatures. The Sn/Ni cathode side is always formed with a uniform Ni3Sn4 layer. At the opposite Ni/Sn anode interface either Ni3Sn4 or NiSn4 could form, which depends on the reaction temperatures and current densities. The results reveal that with a current density of 1000 A/cm2 at 180 °C, the Ni3Sn4 phase remains layer-structured. As the applied current exceeds 2000 A/cm2, Ni atoms are driven by electromigration force to migrate into the Sn matrix to form the irregular bulk Ni3Sn4 and NiSn4. With a higher current density of 5000 A/cm2, large amounts of the Ni3Sn4 phase are distributed into the Sn matrix and even the Ni substrate is seriously consumed. At lower temperatures, below 150 °C and with 5000 A/cm2 current, the plate-like metastable NiSn4 phase is found in the Sn matrix at the anode side. In this electromigration study on the Sn/Ni interfacial reactions, both the reaction temperatures and the applied current densities greatly affect the reaction phase species and their morphologies.