Reliability enhancement of embedded capacitors in printed circuit boards using B-stage epoxy/BaTiO3 composite embedded capacitor films (ECFs)

Epoxy/ceramic composites are one of promising materials as embedded capacitors for a SiP technology, because they have a good processability and a compatibility with printed circuit boards (PCBs), in addition to a high dielectric constant. In this study, we have fabricated embedded capacitors in PCBs using epoxy/BaTiO₃ ECFs, and evaluated their reliability at high temperature aging after moisture absorption. Factors influencing the reliability of epoxy/BaTiO₃ ECF capacitors were analyzed in terms of materials formulation, the ratio of epoxy and BaTiO₃, dispersant contents, and curing agent. From these results, epoxy/BaTiO₃ ECFs materials were optimized in terms of reliability and dielectric properties. And, using these optimized epoxy/BaTiO₃ ECFs, embedded capacitors in prototype-scale, 405 times 508 mm, PCBs were fabricated by conventional multi-layer PCB build-up processes. The total thickness of PCB including embedded capacitors was below 250 mum. And their reliability at high temperature aging after moisture absorption was well qualified.