Abstract: Feed-through vias (38) of 8 mil and smaller diameter are placed on 25 mil centers or smaller so that the feed-through vias serve only as electrical connections and do not block channels between conductors (24a and 42a). The method for forming such feed-through vias and interconnections utilizes metallic resist (36 and 40) which covers the feed-through vias so that the metallic resist, along with conventional photoresist material, prevent undesired etching of the feed-through vias even in the event of misregistration of the photoresist material.

Abstract: Feed-through vias (38) of 8 mil and smaller diameter are placed on 25 mil centers or smaller so that the feed-through vias serve only as electrical connections and do not block channels between conductors (24a and 42a). The method for forming such feed-through vias and interconnections utilizes a metallic resist (36 and 40) which covers the feed-through vias so that the metallic resist, along with conventional photoresist material, prevent undesired etching of the feed-through vias even in the event of misregistration of the photoresist material.

Abstract: Narrow conductors and narrow spaces therebetween, typically two or three mils wide, are fabricated on outer layers of a printed wiring board with built-up areas such as plated-through holes or conductors of widths greater than two or three mils. Gold is deposited over a copper clad substrate in a pattern defining the desired circuitry. Thereafter, solder is placed at the built-up areas and, using both the solder and the gold as resist or masks, the exposed copper is removed by etching. An organic resist material is used in lieu of solder when the built-up area comprises wide conductors or leads, e.g., power busses.