Electroless deposition of copper and nickel on poly(tetrafluoroethylene) films modified by single and double surface graft copolymerization

Surface modification of Ar plasma-pretreated poly(tetrafluoroethylene) (PTFE) films via UV-induced graft-copolymerization with glycidyl methacrylate (GMA) and 1-vinylimidazole (VIDz) was carried out to improve the adhesion with the electrolessly deposited copper and nickel. The surface compositions and microstructure of the graft-copolymerized PTFE films were studied by X-ray photoelectron spectroscopy (XPS) and atomic force microscope (AFM), respectively. Prior to the electroless deposition of the metals, the graft-modified PTFE surfaces were sensitized by SnCl2, followed by activation with PdCl2. The electroless plating of Cu and Ni on the VIDz graft-copolymerized PTFE (VIDz-g-PTFE) film could also be carried out in the absence of sensitization by SnCl2 (the Sn-free activation process). The adhesion strength of the electrolessly deposited metal on the PTFE surface was affected by the type of monomers used for graft copolymerization and the surface graft concentration. The optimum T-peel adhesion strengths of the electrolessly deposited Cu on the VIDz and GMA graft-copolymerized PTFE films were about 2.7 and 6.3 N/cm, respectively. The T-peel adhesion strengths of the electrolessly deposited Ni on the corresponding PTFE surfaces were slightly lower. The T-peel adhesion strengths of the electrolessly deposited Cu and Ni were further enhanced to about 10 N/cm on the PTFE surfaces modified by consecutive graft copolymerizations (double graft copolymerization) with GMA and VIDz.