Ultra-Fine Photoresist Image Formation for Next Generation High-Density PWB Substrate

摘要

System-on-a-Package (SOP) is fast becoming a primary key towards the drive for integration of mixed technologies such as Rf, digital, analog, MEMS and optical at the electronic package level. A key enabler of this technology is a fully integrated substrate, called Single Level Integrated Module (SLIM), with very high wiring density and integrated passive and optoelectronic components. This paper presents an overview of the SLIM testbed integration process and test vehicles, with particular emphasis on ultra-fine resist lithography and microvia processing. This paper will focus on the issues, challenges and results for achieving very fine line and ultra fine line image formation on fiberglass reinforced epoxy substrates for next generation electronic packages. Four commercial photo-resist materials were evaluated for their imaging resolution. The exposure and development processes have been optimized and several related effects, which limit the fine line imaging, have been investigated. Line widths down to 7.5 μm have been achieved at the Packaging Research Center (PRC) on PWB substrates using low cost liquid photoresist and associated processes over a large area.