Surface plasma functionalization of polycarbonate: Application to electroless nickel and copper plating

Electroless metallization of polymers requires different steps including (i ) the preconditioning of the surface to render it chemically reactive, (ii) the chemisorption of a catalyst (Pd) to activate the so-modified surface t owards subsequent metallization, and (iii) the metallization itself. In the present work, electroless metallization was carried out on poly(carbonate) substrates, and step (i) was performed using plasma treatments in various gaseous atmospheres (NH3, N-2, O-2). When a sufficiently high surface conce ntration of nitrogenated groups is grafted it is shown from X-ray photoelec tron (XPS) analyses that the so-functionalized surfaces can chemisorb Pd2ions directly from a simple PdCl2 solution. Thus, step (i) allows simplific ation of the conventional electroless processes commonly used up to now. Mo reover, XPS analyses indicate chemical reduction of Pd2+ ions to Pd(0) duri ng the more or less long initiation time before the start of metallization. This reduction is easily performed in nickel plating baths thanks to the h ypophosphite reducer. On the other hand, this reduction is possible with fo rmaldehyde, the reducer of copper plating baths, only if Sn2+ ions (brought by the conventional processes using SnCl2 and PdCl2 solutions) are present .