Electromigration behavior in Cu/Sn–8Zn–3Bi/Cu solder joint

Electromigration behavior in a one-dimensional Cu/Sn–8Zn–3Bi/Cu solder joint structure was investigated in ambient with a current density of 3.5 × 104 A/cm2 at 60 °C. Due to the compressive stress induced by volume expansion resulting from Cu–Zn intermetallic compound (IMC) growth, Cu5Zn8 IMC layers were squeezed out continuously along IMC/Cu interfaces at both the anode and the cathode with increasing the current stressing time, which was not only driven by the concentration gradient, but also accelerated by the electromigration. And a few voids propagated and formed at the anode and the cathode solder/IMC interfaces during electromigration. Additionally, Sn hillocks occurred in the bulk solder, and Sn hillocks formed at the anode side were larger than those at the cathode side.