LAUSR

Abstract The effects of crystal structure of Nickel on the interfacial phase and growth mechanism were clarified in Sn/Ni soldered joints by using polycrystal nickel and single crystal nickel substrate. It was found that the intermetallic compounds (IMCs) phase, Ni3Sn4, was formed at the interface of Sn/polycrystal nickel joints; while, it changed into NiSn4 when using single crystal nickel substrate. At the following thermal aging process, Ni3Sn4 and NiSn4 exhibited different behaviors: Ni3Sn4 grew faster than NiSn4 showing a much thicker layer. Kinetics analysis indicated that different diffusion mechanisms governed the IMCs layer growth, namely Ni3Sn4 was controlled by diffusion of the reaction elements, whereas NiSn4 was controlled by reaction rate.