Reliability considerations of multilayer printed circuit boards

The temperature resistance of components has steadily increased. Circuits have become increasingly complex. Plated through holes are almost universally used for interplane connections. To improve reliability, multilayer wiring boards which are more heat resistant, more dimensionally stable, and have better electrical properties at high frequencies are needed. While it is possible that commonly used epoxy systems will be improved, many needs can only be met by a totally new resin system. Anticipating that need, RADC has undertaken a comprehensive study program evaluating polyimide resin systems, and comparing them with the commonly used epoxy systems. Polyimide resins are presently available in three types, each having different methods of polymerization. They are addition cure systems, pyrolytic systems, and condensation systems.