The effects and applications of Ge to electronic parts in Pd

In this paper, we focused attention to the grain refiner that is added to palladium plating solution for the purpose of improving the palladium film properties. Generally, arsenic or selenium is added to other precious metal plating solution such as silver plating. In gold plating solution, thallium or lead is added to obtain larger crystal grains for stronger wire bondability. In this way, it has been confirmed that plated film properties vary significantly by adding a small amount of grain refiner to plating solution in just proportion. Thus, it is expected that the preventive effect against the diffusion of metallic impurities from the substrate due to heat treatment is improved by enlarging crystal grain size with the change of film properties through the addition of grain refiner to palladium plating solution. In this study, we have narrowed down its choice of grain refiner to thallium, which is used for gold plating, or germanium and bismuth which are considered as metallic additive. Since germanium showed the most effective result for solder wettability as we evaluated each additive in small amount, the addition effect of germanium was then examined in detail. Furthermore, we focused on the degradation of working environment owing to the ammonia evaporation, which is the conventional problem of Pd plating solution, and thereby developed palladium plating solution having a neutral pH range.