Polymer pretreatments for enhanced adhesion of metals deposited by the electroless process

Metallization techniques based on electroless plating are widely used to coat polymer materials in a large variety of technological applications. Traditionally, dilute tin chloride (SnCl2) and palladium chloride (PdCl2) solutions in HCl are used to render the surface of such non-conductive substrates catalytically active towards metal deposition in the electroless plating solution. In the present work, it is shown how X-ray photoelectron spectroscopy has allowed to monitor the chemical and compositional surface modifications of polymer substrates (polypropylene, polycarbonate) subjected to plasma and UV or VUV irradiation (use of ArF* excimer laser and Xe2* incoherent excimer lamp, respectively) in oxygenated (O2, air) or nitrogenated (N2, NH3) atmospheres, as well as to understand the mechanisms of the catalyst (palladium species) chemisorption on the so-grafted surfaces through the use of a simple dilute palladium chloride solution in HCl. In addition, this work has allowed to bring into light the precise role that the reducer plays (sodium hypophosphite) present in the electroless nickel bath. In short, this research has been successful in allowing the development of new approaches for the electroless metallization of polymer surfaces.