Surface modification of poly(tetrafluoroethylene) films by double graft copolymerization for adhesion improvement with evaporated copper

Abstract

Surface modifications of Ar plasma-pretreated poly(tetrafluoroethylene) (PTFE) film via UV-induced double graft copolymerization were tamed out to improve the adhesion with evaporated copper. The PTFE film surface was first modified by graft copolymerization with a monomer, such as hydroxylethylacrylate and acrylamide, which contained functional moities for curing the epoxide groups. The so-modified PTFE surface was subsequently re- exposed to Ar plasma and subjected to UV-induced graft copolymerization with glycidyl methacrylate. The surface compositions of the PTFE films from single and double graft copolymerization were studied by X-ray photoelectron spectroscopy. The adhesion strength of the evaporated copper on the double graft copolymerized PTFE film was affected by the type of monomer used during the first graff copolymerization, the concentration of the first and second graft, the extent of O2 plasma post-treatment after the second graft copolymerization, and the extent of heat treatment after metallization. The T-type peel strength of the Cu-PTFE laminate obtained under optimum conditions was about 19 N/cm, which represented a more than ten-fold increase over that obtained when the PTFE film was treated by plasma alone. The mechanism of the peel strength enhancement and the cohesive failure of the metal-polymer laminate were also investigated.