Surface Roughening Process Before Plating ABS- Polycarbonate Plastic Chemistry

Polycarbonate and acrylonitrile-butadiene-styrene alloys (PC/ABS) are used widely in many field. In the PC/ABS alloys, the PC phase is used to improve the thermal deformation temperature and the toughness. Besides reduce the cost, the ABS phase is used to improve physical aging, low sensitivity of thickness for impact strength. With the surface metallization of PC/ABS alloys, more specific properties of the PC/ABS resins can be enhanced. Because of the poor wettability and low surface energy, the adhesion strength between the PC/ABS resin and the electroless copper film was weak. Hence, a variety of surface treatment techniques have been developed to functionalize the surfaces property, such as the wet chemical, plasma, UV/ozone and laser treatment. Due to simplicity and low cost, the wet chemical treatment is one of the most used processes for the metallization. A chromic acid/sulfuric acid etching solution is usual applied to obtain favorable adhesion strength between electroless copper film and the PC/ABS substrate. However, the presence of Cr (VI) poses a serious environmental threat, and so, the use of Cr (VI) should be limited as much as possible.PC/ABS substrate is a blend of acrylonitrile, butadiene, styrene and polycarbonate four species, because of the complex composition, it is important for PC/ABS substrate to choose a suitable swelling system. In thesis, four swelling systems were designed to investigate the surface swelling for PCABS substrate. First swelling system is consisting of ethyl acetoacetate (EAA),1-Methyl-2-pyrrolidinone (NMP) and ethanol. Although the surface hydrophilicity of the substrate was improved by the swelling treatment, almost no cavity was formed on the PC/ABS substrate. And so, this swelling system was not suitable for PC/ABS surface swelling. Then the swelling systems containing NMP, ethanol and water was designed for PC/ABS swelling solution. When the concentration of NMP in swelling solution was55%, the surface hydrophilicity and surface topography were improved. When the concentration of NMP in swelling solution was60%, the excessive swelling was found. The optional swelling area was small. Then the swelling systems containing NMP, ethylene glycol monobutyl ether and water was was designed to use, when the concentration of NMP in swelling solution was from20%to40%, swelling temperature form35℃to55℃, the PC/ABS substrate were not well swelled by the solution. When the concentration of the EAA was increased to50%, the surface was swelled well. After etching in MnO2-H3PO4H2SO4etching system with the mole rate of1:1:3.0, the surface hydrophilicity and surface topography was inproved significantly, however, the adhesion strength between the substrate and the Cu film was0.78kN/m.As known, the PC resin is very stable for the strong oxidizing organic or inorganic acids, but the ABS resin is easily oxidized by inorganic acids, and so, it was difficulty for PC/ABS resin to be etched in an etching condition. However, PC resin is easily hydrolyzed in a strong basic solution. A swelling system, containing tetramethyl-ammonium hydroxide (TMAH), and1-Methyl-2-pyrrolidinone (NMP), was used to investigate the surface swelling for PC/ABS. In order to obtain the appropriate swelling conditions for NMP-TMAH-H2O system, when PC/ABS substrates were swelled with NMP-TMAH-H2O solution at35℃for3-10min, the effects of NMP concentration and swelling time on the surface topography, surface hydrophilic were investigated. The results indicated that when PC/ABS substrates were swelled in83%NMP for5min, the etching performance was excellent and the density and amount of the cavities on the surface were increased, the surface contact angle decreased from96°to28°. The results showed that the optinal swelling conditions for NMP system was83%NMP solution at35℃for5min.In order to obtain the optimal etching conditions, when PC/ABS substrates were swelled in NMP-TMAH-H2O swelling system, the effects of etching condition on the surface topography, the surface contact angle and the adhesion strength were investigated. The results showed that when the PC/ABS substrates were etched in the colloid with H2SO4concentration of10.9mol/L at60℃for10min, a good performance and hydrophilic were obtained, and the adhesion strength between PC/ABS substrate and electroless-plated copper reached to1.04kN/m.With the optimal swelling condition and etching condition, the FT-IR spectra of the treated PC/ABS surface was analysed, the new hydrophilic groups such as carboxyl and hydroxyl were formed, which leads to a hydrophilic surface. The Cls spectrum of PC/ABS after swelling treatment and etching treatment were analysisted by XPS. The Cls spectrum of untreated PC/ABS shown four species due to C-C, C-H, C=C (284.9eV), C-O, C=N (286.7eV),-O-CO-0(290.8eV), and n-n*(292.3eV), respectively. After the swelling treatment by NMP-TMAH for5min, a new peak at energy bonding of288.6eV, which is attributed to-COOH peak, appeared. After etching treatment, the -C=O peak at287.6eV and-COOH appeared, which was agreement with the FT-IR spectra.In this work, we found that the swelling process with NMP-TMAH-H2O and the etching process with MnO2-H2SO4-H3PO4were a new effective method, by which an excellent adhesion between electroless copper layer and the PC/ABS substrates was obtained. The improved adhesion of deposited copper to surface of plastics is of great important for the reliability of the metal plating.