Employment of sputtered Ni-Zn films for under bump metallization with Sn-3.0Ag-0.5Cu solder attached during liquid reactions

This study aims to investigate the feasibility of sputtered Ni-xZn films for application as the under bump metallization (UBM). The interfacial reaction under liquid reactions of Sn-3.0Ag-0.5Cu (SAC305) joints with Ni-Zn films will be evaluated. Various kinds of Ni-Zn films were fabricated by sputtering. The surface roughness and residual stress of the Ni-Zn film was evaluated using atomic force microscope (AFM) and the curvature technique. The X-ray diffractometry (XRD) was used to further identify the structure and phases in the films. 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 electrons detector (LABE). Different structure growth in sputtered deposition might lead to distinct IMC formation. The microstructure evolution and phase formation in the SAC305/Ni-7Zn and SAC305/Ni-20Zn joints varied with reflow time. This study demonstrated that the binary Ni-Zn film might be a potential alternative for under-bump metallization application. In addition, the influence of Zn on Ni-Zn films UBM during liquid reactions was discussed and probed.