Improvement of Ga and Zn alloyed Sn–0.7Cu solder alloys and joints

In this study, it is proposed to utilize the advantages of Zn and Ga alloying to achieve improved performance Sn–0.7Cu solder alloys. As dual addition of Ga and Zn into Sn–0.7Cu alloy, wetting force increased while wetting time was reduced simultaneously. Zn promoted the nucleation of β-Sn and lead to the increase of nucleation temperatures. Meanwhile Ga reduced the melting temperature of Sn–0.7Cu. Zn addition introduced another Cu–Zn–Sn intermetallic formation, refined the microstructure. Vickers hardness of Sn–0.7Cu solder alloy and also impact shear strength of Sn–0.7Cu/Ni–Au/Cu solder joints have been obviously improved. The improvements can be attributed to Cu–Zn intermetallic acting as participation phases and solid solution strengthening brought by Ga in β-Sn matrix.