Room-temperature electromigration was monitored in a thin stripe of eutectic Sn-Pb solder which was stressed using a current density of 105A/cm2. Hillocks and voids grew at the anode and the cathode, respectively. It was noted that, although the dominant diffusing species was Sn in the 2-phase alloy, the growth of the hillocks originated from Pb grains. They were extruded under a compressive stress that was due to the incoming flux of Sn atoms. The morphology of the voids at the cathode also indicated that the Sn grains were depleted during the process. A clear relationship was observed between microstructural change and electromigration.

Microstructure-Electromigration Correlation in a Thin Stripe of Eutectic SnPb Solder Stressed between Cu Electrodes. C.Y.Liu, C.Chen, C.N.Liao, K.N.Tu: Applied Physics Letters, 1999, 75[1], 58-60