Creep behavior of near-peritectic Sn-5Sb solders containing small amount of Ag and Cu

Sn-5%Sb is one of the materials considered for replacing Pb-bearing alloys in electronic packaging. In the present study, the effects of minor additives of Ag and Cu on the as-cast microstructure and creep properties of the Sn-5Sb solder alloy are investigated by means of optical microscopy (OM), scanning electron microscopy (SEM), energy dispersive X-ray spectroscope (EDS) and tensile tests. Results show that addition of Ag and Cu resulted not only in the formation of new Ag₃Sn and Cu₆Sn₅ intermetallic compounds (IMCs), but also in the refinement of the grain size of Sn-5Sb solder. Accordingly, the creep properties of the Ag or Cu-containing solder alloys are notably improved. Attention has been paid to the role of IMCs on creep behavior. The lead-free Sn-5Sb-0.7Cu solder shows superior creep performance over the other two solders in terms of much higher creep resistance and vastly elongated creep fracture lifetime. An analysis of the creep behavior at elevated temperatures suggested that the presence of hard Cu₆Sn₅ and fine SbSn IMCs in the Sn-5Sb-0.7Cu alloy increases the resistance to dislocation movement, which improves the creep properties.