A Study on Dielectric Constants of Epoxy/SrTiO3 Composite for Embedded Capacitor Films (ECFs)

Epoxy/BaTiO₃ composites have been of great interest as embedded capacitor materials, mainly due to high dielectric constant of ceramic powders, and good process compatibility of epoxy with printed circuit boards (PCBs). However, one of the potential problems of epoxy/BaTiO₃ composite is the dielectric relaxation at gigahertz range. In this paper, epoxy/SrTiO₃ composite embedded capacitor films (ECFs) were fabricated for high-frequency applications. Dielectric constants of epoxy/SrTiO₃ composite embedded capacitor films with various SrTiO₃ particles loading for three different commercial SrTiO₃ powders were measured, and experimental data were fitted to the Lichtenecker equation for the prediction of the effective dielectric constant of SrTiO₃ powders in epoxy/ SrTiO₃ composite ECFs. Using a rectangular cavity resonator method, dielectric constants of epoxy/SrTiO₃ composite ECFs were measured at gigahertz range (1-10 GHz). At gigahertz frequencies, dielectric constants of epoxy/SrTiO₃ composite ECFs were nearly constant. In contrast, epoxy/BaTiO₃ composite ECFs showed decrease of dielectric constants above 5 GHz. Therefore, it is concluded that epoxy/SrTiO₃ composite ECFs can be more effectively to be applied for high-frequency applications.