Process for producing printed circuit board having improved adhesion

Abstract

A process is disclosed for forming a printed circuit board having improved adhesion of an electrically conductive layer to an underlying dielectric surface. A thin adhesive layer, or film, of conductive material (normally copper) is sputtered onto a dielectric substrate and through holes formed therein, after which the substrate, with the then amorphous sputtered layer thereon, is further processed in a manner so as not to damage adhesion of the sputtered layer to the substrate. The initial step of this further processing can be accomplished chemically or mechanically, and preferably is accomplished by electroplating a buffer, or transition, layer of conductive material onto the sputtered layer with the buffer layer being deposited by placing the substrate, having the sputtered layer thereon, in a first electroplating bath to produce an electroplated layer having no deposit stress or a slightly compressive deposit stress. Additional plating is thereafter carried out in a second electroplating bath having high throwing power, as is needed for plating inside holes for printed circuit applications, and this produces an electroplated layer having tensile deposit stress to thereby provide a uniform conductive material on the substrate and through the holes that is suitable for providing the electrically conductive traces of a printed circuit.