High-density laminate substrates using a non-subtractive manufacturing process

Construction of conventional laminate substrates entails the use of subtractive processes, which have a significant waste and a high environmental impact. In addition, there are circuit density limitations associated with these materials and processes, especially when accounting for cost and yield. In order to address these issues, a DARPA-funded consortial project was initiated, with material suppliers, fabricators, and original equipment manufacturers (OEMs) as participants. The objective of the project is to investigate the materials and associated processes required to build environmentally-conscious, cost-effective, high-density printed wiring boards (PWBs) compatible with direct chip attach (DCA) and other multichip module (MCM)-type applications. Aqueous-developed photodielectric dry film is used in conjunction with several metallization approaches, including electroless copper and conductive ink, to form both vias and circuit traces. This paper will discuss material and process development, test vehicle design and test results, scale-up in a production facility, and environmental impact studies