Study on the epoxy/BaTiO3 embedded capacitor films newly developed for PWB applications

Embedded passives technology is a promising method for miniaturization and higher electrical performance of electronic package systems. High dielectric constant epoxy/ceramic composites have been considered as embedded capacitor materials for organic substrates, because they have processability and compatibility with printed wiring boards (PWB), in addition to high dielectric constant. In this work, we have developed embedded capacitor films with flexibility, processability, and uniform characteristics, and demonstrated an epoxy/BaTiO₃ composite capacitor with small capacitance tolerance could be fabricated using the film. Curing temperature and amount of curing agent were optimized using differential scanning calorimeter (DSC) analysis. Dielectric constant of embedded capacitor films with BaTiO₃ powder volume loading was observed and this behavior is explained using SEM images and density measurement of the films. As a result, using a bimodal mixture of two different size BaTiO₃ powders, a dielectric constant of 100 was achieved. A 7 μm thick capacitor film showed 10 nF/cm² with less than ±5% tolerances, and low leakage current less than 10^-8 A/cm² at 10 V was demonstrated.