Adhesion of copper to poly(tetrafluoroethylene) surfaces modified with vacuum UV radiation from helium arc plasma

Abstract

Poly(tetrafluoroethylene) (PTFE) film surfaces were exposed to vacuum UV (VUV) radiation from He dc arc plasmas that were made to rotate inside a graphite tube by the application of an auxiliary magnetic field. The films were covered with optical filters having different cutoff wavelengths to vary the VUV radiation that modified the fluoropolymer surface. Photo-etching was detected, as well as surface modification that showed the following: (1) water contact angles decreasing with wavelengths of 173 nm or shorter; (2) surface roughening; (3) defluorination of the surface and formation of cross-linking bonds in the top 10 nm of the surface as detected by XPS analysis; and (4) incorporation of oxygen upon exposure to air. An improvement in the adhesion of copper to these modified surfaces was observed.