Investigation on the intermetallic compound layer growth of Sn–0.5Ag–0.7Cu–xGa/Cu solder joints during isothermal aging

Abstract

This work was focused on the influence of Ga on the thermal properties, microstructural evolution and interfacial morphology with aging treatment at 150 °C of low-silver Sn–0.5Ag–0.7Cu (SAC) lead-free solder. The melting temperature of the SAC–Ga solder was decreased owing to the low melting point element Ga and the formations of intermetallic compound (IMC) and growth at the interfaces of SAC/Cu and SAC–0.5Ga/Cu were studied for different aging time ranging from 0 to 720 h. The results indicated that for both solders, the thickness of the IMC increased with aging time prolonging. However, compared with the interface of SAC/Cu, the thickness of the interface of SAC–Ga/Cu was obviously suppressed and the growing speed was slowed down, which may be attributed to the decreased activity of copper atoms by Ga addition, so that the SAC–Ga solder showed relatively planar-like IMC instead of scallop-like at the interface.