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US 4,574,031 AGranted
Additive processing electroless metal plating using aqueous photoresist
AssigneeAT&T Technologies, Inc.
InventorsJohn K. Dorey, II, James T. Huneke, Bruce S. Madsen, Theodore F. Schaaf
Life of this patent
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Abstract
In a method for making a printed circuit board employing an aqueous type photoresist and including etching of the substrate surface with chromic acid after application of the photoresist mask, chromium is washed from the surface with a reducing agent at a pH of .ltoreq.10.
Claims10
A method for making a printed circuit including the steps of:
- (a) applying a photoresist mask to the surface of a substrate to delineate the desired pattern, said photoresist being soluble in an aqueous alkaline solution of pH >10;
- (b) treating the substrate with a chromic acid solution so as to etch the exposed substrate surface;
- (c) washing the substrate in a reducing media having a pH of .ltoreq.10 so as to reduce and remove chrome from the surface;
- (d) catalyze the surface of the substrate;
- and
- (e) electrolessly deposit a thin flash metal deposit from a hypophosphite type flash electroless plating solution.
3 more elements
Dependencies are inferred from the claim text.