The Characteristics of Nickel-Electroplating on Copper Substrate in CO2 Supercritical Fluid

Abstract

In this work, a nickel electroplating was performed on the copper substrate using nonionic surfactant in supercritical carbon dioxide to improve the dispersion characteristics of nickel nano-particles. The electric resistance of emulsion decreased rapidly from 46 to 25 Ω with an increasing pressure from 8 MPa to 16 MPa and was nearly constant at 25 Ω over 14 MPa. The conductivity of emulsion solution was highest at nonionic surfactant concentration of 0.1 vol% and the dispersion of nickel nano-particles was better than at any other concentration. CO2 concentration was controlled under 0.5 vol% to reduce electric resistance in emulsion solution. Roughness (Ra) of copper substrate without plating was 0.084 ㎛, however, that of nickel film plated for 10 min was smoothed to 0.020 ㎛ and the surface of nickel film plated was smoothed with an increasing plating time. The plating properties of nickel in CO2 supercritical fluid showed better properties than in conventional method.