Abstract: It is among the principal objects of invention to provide a composition and a method for improving the adhesion between a copper foil and a printed circuit substrate by the provision of an adhesion promoting copper oxide layer on the copper film.The provision of copper oxide layers on the surface of copper films by immersion in a chlorite-hydroxide bath as conventionally conducted presents problems of safety and reproducibility. This process is improved by employing an oxidizing solution containing an alkali or alkaline earth metal chlorite at a concentration of from 100 grams per liter to complete saturation, and sodium or potassium hydroxide at a concentration of from 5 to 25 grams per liter. The process preferably forms an adhesion improving copper oxide film within commercially practical periods of time, on the order of 7 minutes or less, at practically low temperatures, on the order of from 80.degree. F. to 200.degree. F., and preferably less than about 140.degree. F.

Abstract: It is among the principal objects of invention to provide a composition and a method for improving the adhesion between a copper foil and a printed circuit substrate by the provision of an adhesion promoting copper oxide layer on the copper film.The provision of copper oxide layers on the surface of copper films by immersion in a chlorite-hydroxide bath as conventionally conducted presents problems of safety and reproducibility. This process is improved by employing an oxidizing solution containing an alkali or alkaline earth metal chlorite at a concentration of from 100 grams per liter to complete saturation, and sodium or potassium hydroxide at a concentration of from 5 to 25 grams per liter. The process preferably forms an adhesion improving copper oxide film within commercially practical periods of time, on the order of 7 minutes or less, at practically low temperatures, on the order of from 80.degree. F. to 200.degree. F., and preferably less than about 140.degree. F.