A study on material properties and reliability of Epoxy/ $BaTiO_3$ Embedded Capacitor Films (ECFs) in organic substrates

Abstract

Epoxy/ceramic embedded capacitor films (ECFs) were fabricated using $BaTiO_3$, $SrTiO_3$, specially formulated epoxy resin, and a latent curing agent by a comma roll coating method. Epoxy/ceramic ECFs has coat-ability on a releasing film, good flexibility, tackiness of an uncured film, good adhesion strength, and high temperature stability after cured. Using these ECFs, the capacitors were fabricated on an organic substrate. Their dielectric constants were characterized with a focus on the effects of ceramic fillers, and thermal properties of the ECFs were also characterized with a focus on the effects of epoxy matrix on reliability of the ECF capacitors. Using $BaTiO_3$ and $SrTiO_3$, represented ferroelectric and paraelectric, epoxy/ceramic ECFs were fabricated and characterized in terms of dielectric constant, temperature dependency of capacitance, and dielectric constant at high frequency - GHz range. Dielectric constants of epoxy/ceramic ECFs increased with the volume fraction of the ceramic fillers. The measured dielectric constants of epoxy/ceramic ECFs are well fitted to the Lichtenecker equation, and using this equation, dielectric constants of the ECFs can be predicted. Epoxy/$SrTiO_3$ ECFs showed lower temperature-dependency of capacitance than epoxy/$BaTiO_3$ ECFs. The dielectric constants of epoxy/ceramic ECFs at high frequency, ranging from 1 to 10 GHz, were measured using a rectangular cavity resonator method. The dielectric constants of epoxy/$SrTiO_3$ ECFs at GHz frequency range were not changed with frequency, but those of epoxy/$BaTiO_3$ ECFs decreased above 5 GHz. Thermal properties of epoxy/ceramic ECFs were closely related with those of the epoxy matrix. The temperature coefficient of capacitance (TCC) of ECF was increased abruptly at the glass transition temperature ($\sl{T}_g$) of the epoxy resin. Using multi-functional epoxy, the epoxy resin of the ECFs was newly formulated. A higher $\sl{T}_g$ and a lower coefficient of thermal expa...