Interfacial reaction between Sn-3.0Ag-0.5Cu liquid solder and Ni-xZn novel UBM layers

This work aims to investigate the interfacial reaction under liquid reactions of Sn-3.0Ag-0.5Cu (SAC305) joints with Ni-xZn films by sputtering. The surface roughness and residual stress of the Ni-xZn film, which was regarded to an under bump metallization (UBM), were evaluated using atomic force microscope (AFM) and the curvature measurement. The X-ray diffractometry (XRD) was used to further identify microstructures. Detailed morphology of the interfacial reaction in SAC305/Ni-xZn joints was performed by a field-emission scanning electron microscope (FE-SEM) with low angle backscattered electron detector (LABE). It was demonstrated that the microstructure evolution and phase formation in the SAC305/Ni-7Zn and SAC305/Ni-20Zn joints varied from reflow time and Zn content in the UBM films. The influence of the Zn concentration in Ni-7Zn and Ni-20Zn films on the different interfacial reactions was discussed and proposed.