Relationship between peroxide radical species on plasma-treated PFA surface and adhesion strength of PFA/electroless copper-plating film

Surface metallization process for fluoropolymers with lower environmental impact was studied as a replacement for conventionally used sodium processing with a Pd catalyst. We demonstrated the surface modification of a fluoropolymer to enhance the adhesion of an electroless Cu layer on a poly(tetrafluoroethylene-co-perfluoropropyl vinyl ether) (PFA) surface by combining atmospheric-pressure plasma modification and the grafting of a polymer film. This process allows a high-adhesion interface to be formed without degrading the surface roughness through the graft copolymerization of a poly (4-vinylpyridine) (P4VP) layer as a metal-ion-trapping layer on a PFA substrate. The effect of the plasma treatment time on the adhesion strength was systematically investigated. We found that the surface radical species on the plasma-treated PFA strongly affected the adhesion strength. We achieved a maximum adhesion strength of 0.44 N/mm through the selective formation of side-chain radicals on the PFA surface. It was confirmed that the plasma treatment combined with the plasma-grafting process can be used as an alternative to the conventional copper-plating process with a Pd catalyst.