Western Electric Company, Inc.

At&t Technologies, Inc.

James T Huneke

Theodore F Schaaf

John K Dorey, Ii

John K Dorey Ii

Bruce S Madsen

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.

Additive processing electroless metal plating using aqueous photoresist

A method of forming a flexible printed wiring board having a metal substrate includes the steps of etching through-holes in the metal substrate by means of an etch resistant ferro electric mask placed over the substrate and employing a viscous sealant such as polyethylene or polypropylene glycol between the mask and the substrate. The mask is held to the substrate with the sealant therebetween by means of a magnetic field. The substrate is then treated with a ferric chloride etch solution to etch away the desired through-holes in the metal substrate. Thereafter, the substrate may be coated with a polymeric coated by means of fluidized bed or electrostatic coating techniques as taught in the prior art.

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Lower Makefield, PA, United States of America

James T Huneke