Abs Engineering Plastic Surface Chromium Coarsening The Microetch System Research

With the extensive application of the plastic surface metallization technology, more attention has been paid to the environmental problem caused in surface etching process. More than100thousand ton ABS resins have used for surface metalization annually after surface etching by a chromic acid/sulfuric acid system, which results a serious environmental pollution. In order to reduce environmental pollution, the effects of MnO2-H2SO4-H3PO4-H2O colloids on the surface etching of ABS resin were investigated.Our experimental group had investigated the effects of the treatment condition and the compositions of MnO2-H2SO4-H2O colloids on the surface etching performance of ABS resin, and found that when MnO2content was30g/L, H2SO4concentration was12.3mol?L-1, bath temperature was70℃and treatment time was20min, the ABS surface can be etched effectively, the adhesion between the metallic layer and ABS surface reached to1.19kNm-1. However, there were some defects in this system, for example the treatment temperature was too high, the treatment time was too long and the surface adsorption of palladium ion was poor. These factors restricted its application prospects. In order to solve the problems, phosphoric acid was added to the etching system. Because of a strong coordination of the phosphoric acid, Mn(IV)-phosphoric acid complexes could be formed and the soluble Mn(IV) ion concentration could be enhanced. The increase of soluble Mn(IV) ion concentration in the etching system was a key factor to improve surface etching performance of ABS resin.When the concentration of phosphoric acid was fixed, the effects of the concentration of sulfuric acid upon the etching performance were investigated firstly. The results indicted that:(1) The oxidation potential of etching system was increased with an increase of the sulfuric acid concentration. When the H2SO4concentration in the etching system was9.4mol?L-1, the oxidation potential of etching system was1.307V. The oxidation potential was quickly increased to1.390V, when the H2SO4concentration was11.3mol?L-1. The increase of the oxidation potential strengthens the oxidation capacity of etching system. Because of the phosphate complexation, the optimal oxidation potential reduced from1.426V to1.368V.(2) The soluble Mn(IV) ion contents were lower than0.87g/L in MnO2-H2SO4-H2O colloids, and it increased with an addition of phosphoric acid. And in the MmO2-H2SO4-H3PO4-H2O colloids, when H2SO4concentration was10.7mol?L-1, the soluble Mn(IV) ion concentration in colloids reached maximum (10.60g/L), and then decreased to8.08g/L with an increase of the sulfuric acid concentration in the etching system.(3) With an increase of soluble Mn(IV) ion concentration in etching system, the etching temperature was dereased from70℃to60℃, and the etching time was also dereased from20min to10min. With the proper etching treatment, the adhesion strength increased from1.19kNm-1to1.33kNm-1.The optimal conditions were as follows:C(H3PO4)4.2mol?L-1, C(H2SO4)10.7mol?L-1, MnO260g/L, treatment time10-15min, and bath temperature60℃. With the optimal etching treatment, the average surface roughness of ABS surface was increased from20nm to248nm, and the contact angle was reduced from92.1°to29.6°. FT-IR spectra 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 to6.2%and3.1%respectively. The adhesion strength between the electroless copper film and ABS surface reached1.33kNm-1, which was increased obviously with the etching treatment.We studied the effect of different H3PO4concentration upon etching performance. The results showed that:when the H2SO4concentration was fixed, the main factor to affect the oxidation potential of the etching system was the H3PO4content. When the H2SO4and H3PO4concentrations were10.5mol?L-1and5.6mol?L-1, the oxidation potential of etching system was1.350V. After surface etching, the surface contact angle reduced from92.1°to51.7°. When the H2SO4and H3PO4concentrations were10.5mol?L-1and1.8mol?L-1, the oxidation potential became to1.292V. The surface contact angle was reduced from92.1°to72°with the etching treatment, which indicated that the oxidation potential in the etching system was too low.Eventually, we conclude that the etching process used as MnO2-H2SO4-H3PO4-H2O is a new effective method which can be used to produce an excellent adhesion quality toward metallic layer for ABS plastics. The improved adhesion of deposited copper to surface of plastics is of great important for the reliability in electronic industry.