Abstract: In order to enable fine traces to be obtained on printed circuit boards without excessive undercutting, while maintaining a high degree of adhesion, an unclad FRA board is provided with a surface butter coat which is etched to form a microporous surface layer. This layer is subjected to treatment in a plasma additively reactive with surface groups of the butter coat resin to provide modified groups promoting adherence to a thin metallization layer of vacuum deposited copper. The metallization layer is selectively electroplated to form the desired circuit pattern, and the unplated areas of the metallization layer are etched away.