Via hole structure and process.

摘要

When an insulating film of a multilayer interconnected board or the like is made of two or more coatings so as to build up the required thickness, it can be difficult to provide a via hole with a suitably tapered shape such that when a metallic film for wiring is formed on the composite insulating film, the metal film can completely fill up the via holes. The via holes 7 of the invention are given a gradually increasing diameter from the bottom toward the top of the insulating layer 8 comprising a plurality of preferably photosensitive insulating resin films 2,5, by forming an aperture in each film 2,5 as it is applied, these apertures having successively smaller diameters.