Abstract: All surfaces of a plate having a select pattern of through-holes are coated with a thin metal layer, including the side walls of the through-holes. A layer of a negative dry resist is then laminated onto a plate surface adjacent and facing desired insulating ring zones in such a manner that a portion of the resist layer penetrates into the through-hole orifices. Subsequently, the resist layer portions within the orifices are irradiated with ultraviolet light directed through the through-holes from the surface thereof opposite that coated with the resist layer and then, optionally, another layer of dry resist is applied to this opposing plate surface. Thereafter the resist layer or layers on the plate are irradiated through an appropriate mask aligned relative to the through-hole pattern to define areas for electrodes and the non-irradiated resist areas are stripped-off with a developer.

Abstract: A process or method for producing circuit boards by photo-etching characterized by exposing a first photo-sensitive layer applied to a conductive metal layer on the substrate, removing the unexposed portion of the photo-sensitive layer to expose portions of the metal conductive layer, applying a second metal layer of corrosion-resistant material on the exposed portions of the first metal layer, applying a second photo-sensitive layer, exposing the second photo-sensitive layer using the same mask with the width of the second unexposed pattern, which is an etch-resistant material, being greater than the width of the second metal layer, removing the exposed portions of the second photo-sensitive layer, and etching the first metal layer with a controlled under-etching of the second photo-sensitive layer up to the edges of the second metal layer and then removing the unexposed pattern of photo-sensitive material.