| Polycarbonates (PC) are a kind of engineering plastics with super performance. It has been widely used in industry because of its good impact resistance, heat distortion resistance, high temperature resistant performance and high hardness. The metallization of PC surface can enhance a lot of performance, however, untreated PC surface more smooth level off, lead to the adhesion strength between the PC and copper plating metal layer is very poor. In order to have a successful metallic deposition, a great number of methods have been introduced to enhance the surface roughness and the wetting characteristics of the substrate surface, such as wet chemical, plasma processes, ion track etching, and surface graft copolymerization treatments.Numerous studies have found that a great number of methods have been developed to functionalize the surfaces property, such as the plasma processes, wet chemical, ultraviolet light catalysis and ion etching can be used for surface treatment of PC. Due to simplicity and low cost, the wet chemical treatment is one of the most frequently used processes for the metallization. The wet chemical treatment mainly includes four steps:degreasing, swelling, etching and neutralizing treatments. The swelling and etching treatments are the key steps among them.However, traditional chromic anhydride brings a lot of environmental problems, the use of chromic anhydride should be limited as much as possible. In this dissertation, a newly-designed swelling system was used to swell PC substrate before the etching treatment, the chromium-free and low environmental pollution chemical treatment was used for swelled PC substrate surface etching treatment. Due to the etching treatment principles of the surface of PC different from the ABS, the swelling of the surface has an important role in the etching treatment process. In thesis, four swelling systems were designed to investigate the surface swelling for PC substrate. The first swelling system is consists of1-Methyl-2-pyrrolidinone (NMP), ethanol and water. Although the surface hydrophilicity of the substrate was improved by the swelling treatment, there is almost no cavity formed on the PC substrate by SEM observation. And so, this swelling system is not suitable for PC surface swelling. Then the swelling systems containing NMP, tetramethylammonium hydroxide (TMAH) and water was designed for PC swelling solution. Although the surface hydrophilicity of the substrate was improved by the swe- Iling treatment, there is almost no ideal microporous structure formed on the PC substrate, the surface of microporous aperture is bigger, the depth is shallow by SEM observation. This swelling system is also not suitable for PC surface swelling. We also design swelling systems containing NMP, ethylene glycol diethyl ether and water, when the volume fraction of NMP in swelling solution was from60%to80%, swelling temperature form35℃to50℃, the PC substrate can swelled well by the solution. When the concentration of NMP was increased to75%, the surface was swelled well. After etching in then in MnO2-HsPO4-H2O-H2SO4etching system with the mole rate of1:1:3.5, the surface hydrophilicity and surface topography was improved significantly, however, the adhesion strength between the PC substrate and the Cu film was weak.A swelling system, containing glycol ethylene ether,1-Methyl-2-pyrrolidinone (NMP) and water, was used to investigate the surface swelling of PC. When PC substrates were swelled with1-Methyl-2-pyrrolidinone-glycol ether-water solution at40℃for3-10min, the effects of NMP concentration and swelling time on the surface topography, surface hydrophilic were investigated in order to obtain the appropriate swelling conditions for NMP-glycol ether-H2O system, when PC substrates were swelled with swelling time on the surface topography, surface hydrophilic was investigated. The results indicated that when PC substrates were swelled in70%NMP for5min, the etching performance was excellent and the density and amount of the cavities on the surface were increased, the PC surface became hydrophilic, and the surface contact angle decreased from90.6°to20.2°. The results showed that the best swelling conditions for NMP system were that the sample should be swelled in70%NMP solution at40℃for7min.In order to get the optimal etching conditions, this paper investigated the different etching time and acid concentration of the MnO2-H3PO4-H2SO4-H2O etching system for the change of the surface contact angle, surface morphology and the adhesion strength. The results show that when the V(H3PO4):V(H2O):V(H2SO4)=1:1:3.5, etching time was10min, a good performance and hydrophilic were obtained, and the adhesion strength was improve effectively. When PC substrates were treated with optimal swelling and etching conditions, the new hydrophilic groups such as carboxyl and hydroxyl were formed, which leads to a hydrophilic surface. The Cls spectrum of PC after swelling treatment and etching treatment were analyzed by XPS. The Cls spectrum of untreated PC show four peaks, which are C-C, C-H (285.0eV), C-0(286.6eV), C=O (290.9eV), and π-π*(292.4eV), respectively. After the etching treatment by MnO2-H2SO4-H3PO4-H2O for10min, a new peak at energy bonding of289.0eV appeared, which is attributed to-COOH. It is similar with the FT-IR spectra,In this work, we found that the swelling process with NMP, glycol ether and H2O, the etching process with MnO2-H2SO4-H3PO4-H2O were a new effective method, by which an excellent adhesion between electroless copper layer and the PC substrates was obtained. The improved adhesion of deposited copper to the surface of plastics was of great important for the reliability in high density electronic assembles. |
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