Retardation of (Cu,Ni)6Sn5 spalling in Sn–Ag–Cu/Ni solder joints via controlling the grain structure of Ni metallization layer

Abstract

In the Sn–3.0Ag–0.5 Cu/Ni (wt%; SAC305/Ni) solder joint, the (Cu,Ni)6Sn5 spalling was suppressed by altering the microstructure of Ni films. Ni films with intertwined and straight grain boundaries (GBs) were fabricated by the diverse target powers of the direct current magnetron sputter. The intertwined GB and the straight GB of Ni films determined the degree of the (Cu,Ni)6Sn5 spalling. Ni films with straight GB accelerated the (Cu,Ni)6Sn5 spalling due to the fast diffusion path of Ni and Cu in straight GB of Ni films. In contrast, the winding grain structure of Ni film, called intertwined GB-Ni film, can suppress the interdiffusion of Cu and Ni. Thus, the (Cu,Ni)6Sn5 spalling was successfully retarded by the Ni structure with intertwined GB.