Fluoropolymer surface modification for enhanced evaporated metal adhesion

Abstract Adhesion of evaporated Cu to Teflon PFA (polytetrafluoroethylene-co-perfluoroalkoxy vinyl ether) was greatly enhanced by plasma pretreatment. The efficiency of the treatment decreased in the following order: N2 > O2 > (N2 + H2) > (O2 + H2) > H2. X-ray photoelectron spectroscopy (XPS) showed the loss of fluorine and the incorporation of oxygen and nitrogen at the polymer surface. Among the gases, H2 was found to be the most efficient for fluorine elimination, and (N2 + H2) for surface functionalization. Based on this investigation, it is proposed that Cu reacts with both oxygen and nitrogen to form, respectively, Cu-O and Cu-N bonds at the interface but no reaction occurs with carbon and fluorine. While greater enhancement in polymer surface wettability and stronger interfacial reactions can account for the higher performance of N2 over O2 in improving adhesion, these effects cannot explain the lower efficiency of H2. Several possibilities are discussed, including surface cleaning, oxygen incorporation and the formation of weak boundary layers. Keywords: Teflon PFAplasmasurface modificationCu evaporationadhesionXPS