Epoxy/BaTiO₃ Composite Embedded Capacitor Films (ECFs) for Organic Substrate Applications

Embedded capacitor technology is one of the effective packaging technologies for further miniaturization and higher performance of electronic package systems. High dielectric constant epoxy/ceramic composites have been of great interest as embedded capacitor materials, because they have good process compatibility with multilayer organic substrates applications such as printed circuit boards (PCBs). In this work, it was demonstrated that low (less than ±5%) tolerance epoxy/BaTiO₃ composite capacitors were successfully fabricated on PCBs using newly developed embedded capacitor films (ECFs), which were composed of specially formulated epoxy resin, latent curing agent, and BaTiO₃ powders. And some properties of the capacitors were characterized. Compared with the dielectric layer formation method by spin coating using epoxy/BaTiO₃ suspension, ECFs have excellent advantages such as lower (<5%) capacitance tolerance over large area, no waste of materials, good film formation capability, and processability, long shelf life, and good thermo-mechanical stability after final epoxy cure. Dielectric constant about 93 was obtained using two different size BaTiO₃ powders mixture. Epoxy resin formulation, curing agent, solvents, and dispersant were optimized to produce good film formation capability, fast curing characteristics at 180°C within 5 minutes, good BaTiO₃ powder dispersion control, and excellent shelf life for handling. And the effects of BaTiO₃ particle size and BaTiO₃ powder content on dielectric constant and adhesion strength were investigated. These capacitor films can be embedded on selective areas of PCBs during build-up processes or other substrates such as Si wafers and ceramic substrates.