Chip on chip (COC) and chip on board (COB) assembly on flex rigid printed circuit assemblies

The move to highly populated printed wire assemblies and smaller sized end user products has led to the more common use of flex rigid substrates or the use of flexible substrates. The material most commonly used for the manufacture of flex-rigid and flexible substrates is a polyimide-based resin. This paper details the issues in the mass manufacture of a chip on chip (COC) and chip on board (COB) hybrid on a flex-rigid and flexible substrate, using polyimide as the base material. The paper lists design, process and manufacturing considerations which effects the long term reliability and the yield of the product during the course of the manufacturing process, as well as its useful life