Development of Photolithography Process for Printed Circuit Board Using Liquid Crystal Mask in Place of Photomask

Abstract

In this paper, we present a photolithography method for printed circuit boards using a liquid crystal mask (LCM) in place of a photomask. The LCM photolithography method has the advantage of ease of forming various patterns. There were opaque interpixel regions of the LCMs; the areas on the dry film resist (DFR) located under the interpixel regions of the LCM were not exposed to illumination. The unexposed DFR area could be exposed to illumination by utilizing the Fresnel diffraction effects that were due to a gap maintained between the LCM and the DFR during the exposure process. DFR patterns with a width of 200 mu m were obtained successfully using the 160 mu m gap between LCM and DFR and three sheets of DFR for the exposure process. (C) 2012 The Japan Society of Applied Physics