Filling open through holes in a multilayer board

Abstract

Methods of filling apertures, for example, through holes, in substrates are provided. The methods utilize a dielectric film, preferably a photoimageable dielectric film, which is employed to fill the apertures and to form a dielectric film disposed above the substrate at the same time. As a result, the aperture fill material is the same as, and indeed continuous with, the dielectric film which is disposed on the substrate. The method employs the following steps: providing a substrate having apertures; providing a dielectric film disposed on the substrate covering the apertures, reflowing the dielectric film to flow into the apertures and to form a dielectric film adherent to the substrate, to provide a continuous dielectric extending from the dielectric film into the apertures. In certain embodiments, after filling, additional apertures, such as vias, are photoimaged in the dielectric film. Preferably the vias are then metallized, and circuitry formed atop the dielectric film.