Processing Solution for Base Chrome Etching
Original Publication Date: 1989-Aug-01
Included in the Prior Art Database: 2005-Jan-30
Chrome-Copper-Chrome layered metallurgy is frequently used for circuitization of flexible substrates such as polyimide. The bottom chrome layer enhances adhesion between the metal and polyimide layers; top chrome enhances the corrosion resistance of the circuitry. Circuitry is defined from blanket metal layers by selective etching of the material to leave circuit lines. The metals are often etched in three steps: both chrome layers can be etched by a potassium permanganate/potassium hydroxide solution, separated by a ferric chloride etch for copper and by several water rinses. Typically the final etching of the base chrome layer is followed by an oxalic acid rinse. Oxalic acid is a weak acid and a weak buffering agent.