Shoji Kawakubo

A New Fully Additive Fabrication Process for Printed Wiring Boards

A new fully additive manufacturing process for printed wiring boards is presented, and the performance of boards fabricated by this technology is evaluated. The attainment of satisfactory performance levels using this additive process is achieved by the development of a substrate and an accompanying metallization process having suitable properties. The new process uses commercially available unclad laminates as base materials and includes the following steps: 1) coating and curing of adhesive on the base laminate, 2) drilling of holes, 3) roughening and catalyzing of the adhesive surface, 4) printing negative circuit patterns by screen printing, and 5) formation of conductive circuits by full-build electroless copper plating. Reliability of the through hole interconnection was examined by thermal shock cycle tests. The peel strength between plated copper foils and substrate was measured before and after various heat treatments by soldering. The fully additive process makes it possible to fabricate reliable high-performance printed wiring boards with fewer processing steps than conventional subtractive processes.