Investigation of wet chemical-treated poly(tetrafluoroethylene) surface and its metallization with SIMS, XPS and atomic force microscopy

Surface modification and metallization of poly(tetrafluoroethylene) (PTFE) surface via a wet chemical treatment was studied. The wet process included a pretreatment using Na/naphthalene/THF solution as an etchant followed by an electroless copper plating. The existence of Na in the substrate top lay er down to several micrometers was detected by Secondary Ion Mass Spectrome try (SIMS) and was thought to be the key element which made it possible to deposit electroless copper onto the PTFE surface. The topographies of the p retreated surfaces were examined by SEM and the nanometer-size surface roug hnesses were characterized by Atomic Force Microscopy (AFM). Chemical chang es on the surfaces were characterized by X-ray photoelectron spectroscopy ( XPS) and contact angle measurements. A comparison of copper adhesion was pe rformed by the scribe-grid test and a good agreement with F/C ratio was obt ained. The effects of treatment time and Na/naphthalene ratio on wettabilit y, surface roughness, fluorine removal: copper adhesion as well as the locu s of failure are discussed.