Shear strength and interfacial microstructures of low-Ag SAC/Cu and SAC-Bi-Ni/Cu solder joints

Recently, the development of low-Ag Sn-Ag-Cu (SAC) solders has become a new research field in electronic packaging industry because of the braze reliability and cost concerns. In this study, the shear strength and interfacial microstructures of two kinds of low-Ag solder joints, SAC/Cu and SAC-Bi-Ni/Cu, were investigated. The results obtained affirmed that the addition of Ni and Bi in low-Ag SAC0705 solder improves the shear strength of the solder joints and decreases the fracture ductility of the alloy. With 3.5% Bi and 0.1% Ni addition, the shear strength increases from 11.09MPa to 19.51MPa. For low-Ag solder joints investigated in this research, the shear dimples mostly appear at the interface between bulk solder and interfacial IMC.