Study of an Environmentally Friendly Surface Etching System of ABS for Improving Adhesion of Electroless Cu film

Abstract

In this paper, an environmentally friendly system containing H2SO4-MnO2 colloid was used to investigate surface etching of acrylonitrile-butadiene-styrene (ABS) resin as a replacement for the chromic acid etching solutions. The effects of the H2SO4 concentrations, bath temperatures and etching times on the etching effectiveness were studied. The surface roughness and surface hydrophilicity of ABS substrates were improved greatly with the etching treatment. After the electroless plating of copper, the adhesion strength between the electroless copper and ABS substrate reached 1.19 KN m−1, which was much higher than that required in PCB process (over 0.7 KN m−1). Electrical potential measurements indicated that the etching performance depended strongly on the oxidation potential of MnO2 and the “soluble” MnO2 concentration in the colloid. The FT-IR spectra and XPS results demonstrated that the C=C bonds of butadiene on the ABS surface were oxidized, and –COOH and –OH groups were formed on the ABS surface with the etching treatment. Meanwhile, some –C≡N groups of acrylonitrile were changed to –CONH2 groups with etching treatment, and the –CONH2 groups increased with the etching time. The formation of –COOH, –OH and –CONH2 groups on the surface enhanced hydrophilicity and decreased surface contact angle, which was beneficial to improve the adhesion strength. These results suggest that the H2SO4-MnO2 colloid is an effective and environment-friendly surface etchant for ABS surface etching.