Abstract
The purpose of this study is to investigate the effect of Ni addition to low Ag lead-free solder on the mechanical properties of solder joints by tensile test and their fracture surfaces. It is found that the Ni added specimens form plain interfacial reaction layer, and suppress the occurrence of cracks into the reaction layer. Ni addition increases the solder/Cu joint strength because of fine Sn primary phase. The fracture position changes from the inside of solder bulk to the vicinity of the interface between reaction layer and solder bulk or into the interfacial reaction layer. And then fracture mode changes from ductility to brittleness.
