Bright nickel film deposited by supercritical carbon dioxide emulsion using additive-free Watts bath

This paper is aimed on studying film smoothening effect of supercritical carbon dioxide emulsion (Sc-CO 2-E) on nickel film electroplated using an additive-free Watts bath. Morphology of nickel film electroplated with Sc-CO 2-E was found to be similar to that of nickel film prepared from electroless plating. Surface roughness ( R a) of nickel film electroplated with Sc-CO 2-E was lower than that of nickel film electroplated through conventional method. A minimum R a was found for nickel film electroplated through conventional method and Sc-CO 2-E when increasing current density from 0.010 to 0.150 A/cm 2. The minimum R a was 69.8 nm at 0.020 A/cm 2 and 14.0 nm at 0.030 A/cm 2, respectively for conventional and Sc-CO 2-E case. After the minimum point, increasing rate of R a increased was lower for Sc-CO 2-E case; this was because of higher hydrogen solubility in Sc-CO 2. Grain size of nickel film electroplated with Sc-CO 2-E was found to be finer than that of conventional case.