Morphology and growth mechanisms of SAC305-xNi/pad joints intermetallic compounds

摘要

The formation and growth of intermetallic compounds (IMC) is a key factor to the reliability of soldering joints in modern electronic mounting and packaging industry. In this paper, by means of Olympus, scanning electron microscope (SEM) and Energy Dispersive X-ray (EDX) analysis methods, the morphology and growth mechanisms of IMCs between SAC305-xNi and Cu joint during soldering as well as aging were studied. Ni addition made IMC of SAC305/Cu joint turn into (Cu1-x, Nix)6Sn5 which appeared irregular island shape. The content of Ni in the IMC was different as the aged time prolonged. The average content of Ni in the SAC305-0.1Ni/Cu joint IMC which showed an increasing tend from the side near Cu to the bulk solder side was 5wt%. However, the two regions which average content of Ni in the SAC305/Ni joint IMC was respectively 17wt% and 7wt% showed a descending tend from the side near Ni to the bulk solder substrate side. It would force the type transformation to form (Ni, Cu)3Sn4 when the content of Ni was more than 22wt.% in the SAC305-0.1Ni/Ni joint IMC. The formation and evolution physics model of IMC was established by analysis of SAC305-x(Ni, Bi)/pad interfacial microstructure.