Plastic-metal composite and method of making the same

Abstract

The improved plastic-metal unitary composite of the invention formed by the present method, includes (a) a thin copper foil, for example, weighing about 1 or 2 ounces per square foot, one side of which has a rough irregular surface with improved bondability to plastic but increased propensity for staining, (b) a thin layer of metal selected from Cr, Al, Cd or a Cd alloy of Sn, Zn or Cu, or a mixture thereof, encapsulating the rough surface so as to decrease its staining characteristic without substantially descreasing its bondability, and (c) a plastic substrate bonded to the encapsulating layer. The rough irregular surface of the foil includes a plurality of discrete particles of copper and/or copper oxide adherent to the copper foil but detachable therefrom and embeddable in the plastic. However, the encapsulating metal layer, substantially reduces such detachment and embedding and thus substantially reduces, as noted above, undesirable staining which commonly occurs during utilization of such composites in the manufacture of such items as printed circuit boards and the like. These advantages are achieved while reducing the tendency of fine lines of copper conductor made therefrom on the circuit boards to lift from the substrate. Processing of the boards is facilitated, since standard etching solutions can be employed.

Dependencies are inferred from the claim text.