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 ∼1 μm and a thickness of ∼2.2 μm, was accomplished at a pressure of 2.4 mTorr and 200 W power. After polishing, a uniform thickness of 1800 nm with a mean roughness (Ra) of 14.9 nm was obtained. The samples contained polycrystalline β-Sn grains at (200) diffraction planes with a preferred orientation 2θ of 30.70°. Although the XRD pattern did not indicate any Ag peaks, weak peaks of Ag₃Sn were observed at 2θ of 37.60° and 39.59°, 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 μΩ 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.