| With the extensive application of the plastic surface metallization technology, more attention has been paid to the environmental problem caused by the surface etching process. More than100thousand tons ABS plastic have been used for surface metalization annually after surface etching by a chromic acid-sulfuric acid system, which results in serious environmental pollution. In order to reduce environmental pollution, the effects of MnO2-H2SO4-H3PO4and MnO2-H2SO4-Na5P3O10colloids on the surface etching of ABS plastic were investigated.The surface etching of ABS plastic was studied using a solution comprising of MnO2, H2SO4and Na5P3O10. The results show that:(1) When the concentration of sulfuric acid was fixed, the oxidation reduction potential of etching system was increased with an increase of the phosphoric acid concentration. Because of the phosphate complexation, the optimal oxidation reduction potential reduced from1.426V to1.342V.(2) The soluble Mn(IV) ion content of etching system was first increased and then decreased with an increase of the H3PO4concentration. When the H2SO4and H3PO4concentrations were12.5mol/L and0,94mol/L respectively, the soluble Mn(IV) ion concentration in colloids reached a maximum of4.98g/L, and then decreased to3.55g/L with an increase of the H3PO4concentration, suggesting that phosphoric acid has good complexation in etching system.(3) With the proper etching treatment, the adhesion strength increased from1.19kN/m to1.29kN/m. The optimal conditions were as follows:CH2SO4(12.5mol/L), CH3PO4(0.94mol/L), MnO2(60g/L), treatment time10min, and bath temperature60℃. The contact angle of ABS surface was reduced from92.1°to33°, and the adhesion strength between the electroless copper film and ABS substrates surface reached1.29kN/m.In order to expand the research field, NasP3O10was added into the MnO2-H2SO4system to constitute a new system of MnO2-H2SO4-NasP3O10, Mn(IV)-sodium tripolyphosphate complexes could be formed. The effects of MnO2-H2SO4-NasP3O10colloids on the surface etching of ABS plastic were investigated.The adhesion strength can be improved significantly by a low pollution etching system comprising of manganese dioxide, sulfuric acid, sodium tripolyphosphate. The relationship between the composition of etching solution and its oxidation capacity were analyzed by the measurement of oxidation reduction potential and soluble Mn(IV) ion concentration. The effects of the H2SO4concentration and Na5P3O10content on the surface topography and the adhesion strength were studied. When fixed the concentration of sulfuric acid, the oxidation reduction potential of etching system was decreased with the increase of the sodium tripolyphosphate concentration, because of the reaction of sulfuric acid and sodium tripolyphosphate system. When the H2SO4concentration was13.5mol/L and the Na5P3O10content was60g/L, a good etching performance was obtained. Many cavities appeared on the ABS surface and the density and depth of cavities were large, the roughness reached the maximum, and the ABS surface changed from a hydrophobic to a hydrophilic, as well as the adhesion strength increased from1.19kN/m to1.25kN/m. The optimal conditions were as follows: CH2so4(13.5mol/L), Na5P3O10(60g/L), treatment time10min, and bath temperature60℃. The contact angle of ABS surface was reduced from92.1°to30.5°, and XPS analysis results indicated that a great amount of carbonyl and carboxyl were formed on the surface of ABS substrate with an etching treatment and the content of carbonyl and carboxyl reached to6.8%and6.1%respectively. The adhesion strength between the electroless copper film and ABS substrates surface reached1.25kN/m.In this work, we conclude that excellent adhesion strength between electroless copper layer and the ABS substrates surface was obtained in the etching process of MnO2-H2SO4-H3PO4and MnO2-H2SO4-Na5P3O10, which were low pollution etching systems. The improved adhesion strength played a great important role in the electronic industry. |
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