Size effect of BaTiO3 on the properties of epoxy/BaTiO3 composite film

With the increasing needs for higher functionality and higher performance of electronic devices, the packaging technology is developing toward functionalization of the inner space of printed-wiring-boards (PWBs) by embedding active or passive components. As a passive component, embedded capacitors have been actively investigated, because they occupy about 40% amount of surface area on a substrate. Ceramic-Polymer composite is one of the candidate materials for embedded capacitor because it combines the high permittivity of the ceramic and the good processing of the polymer. The dielectric constant of the commercial embedded capacitor materials is usually lower than 25. In this study, we increased the packing density of the films by mixing BaTiO₃ with different size (50 nm and 200 nm) to enhance the dielectric constant of BaTiO₃-epoxy composites. The thickness of the films was 17 μm. The dielectric constant was increased with the increase of packing density. When the loading of BaTiO₃ was 80 wt%, the dielectric constant of BaTiO₃-epoxy composites with 50 nm and 200 nm BaTiO₃ was 19.5 and 21.5 at 1 kHz, respectively. And the two types of BaTiO₃ were mixed with 71 wt% of 200 nm and 17 wt% of 50 nm BaTiO₃, the dielectric constant of the film was increased to 27 at 1 kHz. At the same time, the dielectric loss was at a low value. The color of the coating films turned from almost transparent to white when the content of 200 nm BaTiO₃ was increased. It suggested that light-penetrating property was enhanced for the films filled with small size particles. The glass transition temperature and the 90° peel strength were also enhanced by increasing the content of 200 nm BaTiO₃. Therefore, when the 200 nm BaTiO₃ at a high loading was suitably mixed with 50 nm BaTiO₃, high performance embedded capacitor materials could be obtained.