| dc.description.abstract | Amounts of corrosive gas affect the reliability of electronic devices. In order to prevent corrosion reaction on automobile printed circuit broads (PCBs), surface finish is adopted to protect the surface of PCBs. In this investigation, PCBs were coated several metallic thin films on the surface, such as electroless nickel immersion gold (ENIG), immersion tin (ImSn), electroless cobalt (EC), and electroless cobalt immersion gold immersion tin (ECIGS). The air-tight clave, pumping the SO2 gas, was utilized to explore the anticorrosion capability and the corrosion products for samples. The concentration of SO2 gas was either 15 or 1500 ppm at 80 oC for 48 and 120 h. The humidity was processed with 100% relative humidity (RH) to confirm the water-film on the surface. Negligible corrosion products formed on the surface after 15 ppm SO2 for 48 and 120 h. The multiple corrosion products formed and covered whole sample on the ENIG surface after 1500 ppm SO2 for 48 h. At the same condition, corrosion products some grew on the ECIGS surface. In addition, slight corrosion products formed on the ImSn and EC after 1500 ppm SO2 for 48 h. When exposed time increased to 120 h, the corrosion products covered whole the ENIG and EC samples. Additionally, Cu signals was observed on the corrosion products for ENIG, ImSn, and EC but not on the ECIGS. The surface finishes also were investigated by electrochemical analyses such as Tafel test. According to Tafel curve, ECIGS was stable coating in this investigation. The results of transfer coefficient showed that reduction reaction dominated when EC sample immersed in the 0.5 M H2SO4. The ECIGS exhibited the effective anticorrosion capability for high reliability device in this investigation. | en_US |