Abstract: Copper-containing surfaces, such as a copper surface for use in an electrical circuit, are protected by the provision of a bismuth metal coating immersion-plated from a moderately to strongly acidic plating bath. The plating bath preferably contains dissolved bismuth, halide, and a sulfur-containing ligand as a complexing agent that promotes adhesion of the bismuth coating. The bath may be formed from a concentrate system combined with water. The concentrate system may be a two-component system having an acidic first component containing the bismuth, halide, and sulfur-containing ligand, and an alkaline second component containing an additional complexing agent (e.g., EDTA salt). Tarnish resistance of the plated bismuth can be improved by the application of an alkaline composition to neutralize residual acid. Plating thickness can be enhanced by pre-cleaning the surface to be plated with a pre-cleaner containing nitric acid.

Abstract: A post-treatment method for copper on printed circuit boards is disclosed. The method comprises forming a cupric-based organometallic conversion coating on a copper surface of a printed circuit board, and then converting the cupric-based organometallic conversion coating to a cuprous-based organometallic conversion coating. The resulting cuprous-based organometallic conversion coating is desirable in that it improves copper to dielectric bond integrity.

Abstract: A process used during manufacture of printed circuit boards comprises protecting metal pads and/or through-holes to provide a tarnish-resistant and solderable coating. In the method, the pads and/or through-holes are bright-etched, metal plated, preferably by an immersion process, and treated with a tarnish inhibitor. The tarnish inhibitor may be incorporated into the immersion plating bath. The metal plating is usually with silver or bismuth and the pads and/or through-holes comprise copper.

Abstract: A metal dissolving liquid and method for stripping solder and the underlying tin-copper alloy from the copper substrate of a printed circuit board, including an aqueous solution of nitric acid in an amount sufficient to dissolve solder and tin, a source of ferric ions in an amount sufficient to dissolve tin-copper alloy, a source of halide ions in an amount sufficient to solubilize tin, and a source of ammonium ions in an amount sufficient, in combination with the halide ions, to solubilize the tin and substantially eliminate sludge formation, reduce attack on the copper substrate and provide a bright copper finish after solder removal. A liquid further including benzotriazole and urea in amounts not more than about 2% by weight of each. The liquid wherein the source of ammonium ions includes ammonium bicarbonate.