Effects of Ga addition on microstructure and properties of Sn-Ag-Cu/Cu solder joints

The effects of Ga alloying on melting behaviors of the SnAgCu solder, the interfacial reaction behaviors and mechanical properties of the SnAgCu/Cu solder joints were investigated in this study. The melting behaviors of the Sn3.5Ag0.7Cu1.5Ga solder alloy was analyzed firstly and compared with the Sn3.5Ag0.7Cu solder, then the interfacial microstructure, shear and fatigue properties of the SnAgCu/ Cu and SnAgCuGa/Cu solder joints were studied. It was found that addition of Ga element can obviously decrease the melting point of the SnAgCu solder. During the soldering process, the Ga element forms the Cu2Ga phase around the joint interface, which decreases the growth rate of the interfacial intermetallic compounds layer. Shear strength of the SnAgCuGa/Cu solder joints are slightly higher than the SnAgCu/ Cu solder joints, and their fatigue properties are about the same. Under different mechanical loadings, there is no fracture occurs at the Cu2Ga/solder interface or the Cu2Ga/Cu6Sn5 interface, neither in the Cu2Ga phase, indicating that the Ga addition has little negative effect on interfacial mechanical property of the SnAgCu/Cu solder joint. (C) 2014 Elsevier B. V. All rights reserved.