Effects of Ce and Zn additions on the microstructure and mechanical properties of Sn–3Ag–0.5Cu solder joints

It has been reported that the rapid growth of tin whiskers occurring on the surface of rare earth containing solders can be prevented by the addition of 0.5 wt.% Zn into a Sn–3Ag–0.5Cu–0.5Ce alloy. The present study shows that the tensile strength of Sn–3Ag–0.5Cu–0.5Ce alloy alloyed with Zn increases significantly in comparison to the Zn-free Sn–3Ag–0.5Cu and Sn–3Ag–0.5Cu–0.5Ce solder. Moreover, the growth of intermetallic compounds at the solder/pad interfaces during the thermal aging at 100 °C and 150 °C was inhibited by the Zn addition. Nevertheless, the excess of Zn addition to 0.5 wt.% causes poor junction in the Sn–3Ag–0.5Cu–0.5Ce packages. An optimized addition amount of Zn in Sn–3Ag–0.5Cu–0.5Ce solders is 0.2 wt.% for both inhibiting the growth of tin whiskers and strengthening the solder joints, although its ductility is still lower than that of the original Sn–3Ag–0.5Cu.