Adhesion improvement of ABS resin by MnO₂-H₃PO₄-H₂SO₄ colloid with ultrasound-assisted etching treatment

The adhesion strength between electroless copper and acrylonitrile-butadiene-styrene (ABS) resin could be improved significantly by MnO2-H3PO4-H2SO4 colloid system. In this paper, when the concentrations of H3PO4 and H2SO4 in the colloid were 4.2 and 10.4 M, respectively, the effect of the ultrasound-assisted etching (UAE) time on the etching performance of ABS resin were investigated. With the UAE for 10 min, much more uniform cavities formed on the ABS surface, the average surface roughness (Ra) decreased from 143 to 107 nm, which was much lower than etched by CrO3-H2SO4 colloid (420 nm). Though the average surface roughness (Ra) was decreased, the average adhesion strength between the electroless copper film and ABS substrate increased from 1.39 to 1.60 kN m−1, which was also higher than chromic acid etching treatment (1.42 kN m−1). The density of the hydrophilic groups and the uniformity of cavities on the ABS surface were increased with the UAE, which resulted in high adhesion strength and low average surface roughness.