Plasma chemical modification of polycarbonate surfaces for electroless plating

The preliminary steps of the "electroless" metallization of polycarbonate are investigated by XPS. They consist of the chemisorption of a catalyst (Pd) on the surface to be metallized. The corresponding surface can be activated either by chemical etching or by reactive or non-reactive gas plasma treatment. Therefore, the surface treatment of polycarbonate determines the palladium adsorption. It is shown here that a surface carrying oxygenated functions adsorbs palladium through Sn2+ ions which are themselves bonded to oxygen atoms. On the other hand, a surface on which nitrogenated groups have been grafted (by NH3 or N-2 plasma treatment) chemisorbs palladium directly on these nitrogen atoms. Reaction mechanisms are proposed in both cases and a new and simplified process for making the surfaces catalytic is proposed.