2008 Volume 57 Issue 2 Pages 96-101
Silver, a typical electronic material, corrodes in sulfur gas released from rubber. To evaluate the corrosion damage, we established a method for estimating concentration of sulfur gas released from rubber. Firstly, we showed that the silver corrosion behavior in sulfur gas released from rubber is similar to that in sulfur gas released from sulfur flower using a boxy-vessel test. Moreover, the corrosion product on silver was Ag2S only, and the thickness of the corrosion product increased linearly with exposure time. We also found that the silver corrosion rate in the boxy-vessel test depends on both the corrosion reaction and the diffusion of sulfur gas. The former mainly determines the silver corrosion rate. The corrosion rate was therefore calculated by corrosion analysis considering the sulfur gas diffusion and corrosion reaction. Under the condition that the corrosion analysis assumed an inverse problem, the concentration of sulfur gas released from rubber was estimated from the corrosion rate measured by a pre-experiment. By using the corrosion analysis under the boundary condition of concentration of sulfur gas released from rubber, we can estimate the silver corrosion rate in the space of electronic equipment where silver coexists with rubber. We can therefore verify effective countermeasures against corrosion and ensure the corrosion reliability of electronic equipment.