METHOD OF REWORKING THE WHOLE SURFACE OF MULTILAYER CIRCUITS WITH DEFECTIVE OUTER COPPER CONDUCTOR LAYERS

摘要

After cleaning and removal of oxidic layers, the defective copper conductors are completely etched off the surface of the external planes of a multilayer circuit board, and the copper on the walls of the plated through holes is etched at an etching rate continuously decreasing toward the center of the hole walls. Subsequently, an activating layer of copper is applied on the surface of the substrate and on the adjacent parts of the surface of the hole walls. Copper conductors defined by a photoresist mask in a known manner, are deposited on the surface of the activating layer following the additive technique, the copper is deposited on the entire surface of the hole walls. As the maximum etching depth of the copper on the hole wall is approximately 0.2 mm maximum, and as the activating layer is applied up to a depth of approximately 1.2 mm a perfect copper overlap on the walls is ensured.