Patent ID: 7955783
Filing Date: 2011-06-07
Classification: H05K

Abstract:
1. A method for forming a pattern of electrical contact regions over a non-conductive substrate on which electrical traces have previously been formed on a front side and through which at least one via has previously been formed connecting the front side of the substrate to a back side of the substrate, said via having a conductive material selectively deposited on a sidewall thereof to provide an electrical interconnection between said front side of the substrate and said back side of the substrate and further defining an open channel in a central region of the via between the conductive material formed on the sidewall of said via, comprising the steps: forming a layer of photosensitive material over the electrical traces and the non-conductive substrate; depositing a film over the photosensitive material, said film transparent in a first wavelength band; depositing droplets of material opaque in said first wavelength band in a pattern on said film so as to form a photomask thereon, said photomask formed at least over said via, including said conductive material selectively deposited on a sidewall of said via and said open channel; exposing said photosensitive material to light in said first wavelength band in regions other than directly below the photomask pattern of droplets; removing said film and said photomask pattern of droplets; developing said photosensitive material so as to remove regions of said photosensitive material not exposed to said light in said first wavelength band, thereby exposing selected regions of said electrical interconnections and said non-conductive substrate whereby said photosensitive material is removed over said via, exposing said conductive material selectively deposited on said sidewall of said via and leaving said channel open and unfilled.