Microstructure, creep properties, and electrical resistivity of magnetron sputtering deposited SAC305 thin films

This paper investigates the surface morphology, mechanical properties, and electrical resistivity of 96.5Sn-3.0Ag-0.5Cu (SAC305) thin films deposited on Si and SiO2 substrates through RF magnetron sputtering. Various deposition parameters were tested using both DC and RF power sources at different pressures and powers to produce robust continuous films. The most optimal surface morphology, with an average grain size of similar to 1 mu m and a thickness of similar to 2.2 mu m, was accomplished at a pressure of 2.4 mTorr and 200W power. After polishing, a uniform thickness of 1800 nm with a mean roughness (Ra) of 14.9 nm was obtained. The samples contained polycrystalline beta-Sn grains at (200) diffraction planes with a preferred orientation 2 theta of 30.70 degrees. Although the XRD pattern did not indicate any Ag peaks, weak peaks of Ag3Sn were observed at 2 theta of 37.60 degrees and 39.59 degrees, corresponding to diffraction planes (020) and (211), respectively. The electrical resistivity of the SAC305 thin film deposited on the SiO2 substrate and of the bulk SAC305 samples were measured as 19.6 and 13.7 mu Omega cm, respectively. It was noted that changes in hold time at peak loads or the rate of loading in the creep experiments did not significantly influence the creep properties of the SAC305 bulk or thin film material.