Novel polyimide printed circuit boards

Printed circuit boards using polyimide or modified polyimide matrices have been under exploratory study for most of the past decade. The major driving force behind this work has been the need for improved service reliability in the field along with the harsh economic necessity to cut scrap losses in the manufacturer´s plant. As a polymer class the polyimides offered improved thermal stability and chemical resistance versus the standard epoxy systems. Thus, it was expected that boards using polyimide matrices would show less change in electrical and physical properties during the manufacturing cycle and also in their daily use. For example, short term exposure of epoxy boards to soldering temperatures can cause the breakdown of the matrix with a resulting change in the physical and electrical properties of the board at that particular spot. Drilling is another manufacturing process where boards are subjected to high temperatures for short terms. Again physical changes such as smearing will occur and the extent of these changes depends primarily on the properties of the polymer matrix; thus, the search for polymer systems having thermal stability both short and long term.