Manganese Dioxide - Phosphoric Acid - Sulfuric Acid Micro-corrosion System For Micro-pitting On The Surface Of Abs Plastic

Though the surface metallization technology of plastic has been used widely in production, more attention is paid on the environmental problem of its surface etching. Nowadays, surface etching for plastics was carried out by chromic anhydride/sulfuric acid solution, which cause serious pollution to the environment of Cr(Ⅵ). In order to reduce the pollution, the effects of environment-friendly MnO2-H3PO4-H2SO4 colloid on the surface etching of ABS resin were investigated.Because the solubility of MnO2 was less than that that expected, the ABS surface could not be etched effectively in a short time, which causes that MnO2-H2SO4 system was not used widely in industry. In the thesis, H3PO4 was introduce the MnO2-H2SO4 system to increase the solubility of Mn(IV) ions in the system, because Mn(Ⅳ) ions could be coordinated by H3PO4. At first, the open circuit potential of MnO2-H2SO4 system was measured. When the redox potential was 1.426 V, the etching performance was better. Based on the redox potential of the etching system, the component of MnO2-H3PO4-H2SO4 system was speculated. When the ratio of volume (H2O:H3PO4:H2SO4) was 1:1:2.5 and the content of MnO2 was 60 g/L, the oxidation-reduction potential of the system was 1.340 V, which was lower than that of MnO2-H2SO4 system. The effects of different components of MnO2-H3PO4-H2SO4 system on the etching performance were studied. The surface topography and hydrophily of ABS before and after the etching process were measured by SEM, AFM, surface contact angle, ATR-IR and XPS.When ABS substrate was treated in H2O:H3PO4:H2SO4 colloid (v:v:v=1:1:2.5) at 70℃for 10 min and MnO2 was kept at 60 g/L, a good etching performance was obtained. The average roughness (Ra) increased from 34 nm to 143 nm, and the contact angle decreased from 92.1°to 33.4°. After etching 10 min, a large number of carboxyl and carbonyl groups appeared on the surface, the content of carbon decreased, the content of C=O and -COOH increased. The adhesion strength between ABS substrate and copper film increased to 1.35 kN/m, which was close to the adhesion strength etched by CrO3/H2SO4 (1.42 kN/m).In addition, surface etchings of ABS with an ultrasound-assisted treatment in MnO2-H3PO4-H2SO4 system were studied. After ultrasound-assisted treatment for 10 min, the adhesion strength increased to 1.60 kN/m, and a significant improvement of adhesion strength was obtained.Finally, MnO2-H3PO4-H2SO4 system was an environmental friendly chemical etching system. The improvement adhesion of deposited copper to plastic's surface was of great importance for the reliability in high density electronic assembles.