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EpoxylBaTiO3 composite embedded capacitorfilms (ECFs) were newly designedfor high dielectric constant and low tolerance (less than +5%o) embedded capacitorfabricationfor organic substrates. In terms of materialformulation, ECFs are composed ofspeciallyformulated epoxy resin and latent curing agent, and in terms ofcoating process, a comma roll coating method is usedfor uniform film thickness in large area. Dielectric properties ofBaTiO3(BT)& SrTiO3 (ST)composite ECF is measured MIM capacitors with oxygen plasma etched ECFs on 0X10 cm PCBs. For JX1 mm capacitors with 12 um thickness and 50 vol.0 %BTO ECFs, dielectric constant of39, dielectric loss of0. 01 7, capacitance density of2.4 nF/cm2, and less than 10% tolerance were obtained. Dielectric constant ofBTECF is bigger than that ofSTECF, and it is due to difference ofpermittivity ofBT and SrTiO3 particles.Dielectric constant ofBT & ST ECF in highfrequency range (0. 5-l OGHz) is measured using a cavity resonance method. In order to estimate dielectric constants at highfrequency, the reflection coefficient is measured with a network analyzer. Dielectric constant is calculated by observing thefrequencies ofthe resonant cavity modes. Although there was no dielectric relaxation observed at pure epoxy, for BTECF, there is the dielectric relaxation at 5-9GHz. It is mainly due to changing ofpolarization mode ofBTpowder itself In contrast, there is no relaxation for STECF up to 10GHz. Alternative materialfor embedded capacitorfabrication is epoxy/BT composite embedded capacitor pastes (ECPs). It uses similar materials formulation like ECFs and a screen printing methodforfilm coating. The screen printing method has the advantage offorming capacitor partially in desired area. But the screen printing makes surface irregularity during maskpeel-off Surfaceflatness is significantly improved by adding some additives and by applying pressure during curing. As a result, dielectric layer with improved thickness uniformity is successfully demonstrated. For 4X4 mm capacitors with 1] um thickness and 50 vol.% BT ECFs, dielectric constant of39, dielectric loss of 0. 023, capacitance density of2.6 nF/cm2, and 22% tolerance were obtained.

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In this study, the temperature dependence of capacitance, one of the most important properties of embedded capacitor films (ECFs), was investigated. The temperature dependence of the capacitance of ECFs was determined by the temperature dependence of the dielectric constant and thickness, and among these, the main factor was the dielectric constant of ECFs. The dielectric constant of ECFs was determined by that of epoxy and BaTiO 3 powders. Below 130°C, the dielectric constant of ECFs increased as temperature increased, and was mainly affected by an epoxy matrix. However, above 130°C (the Curie temperature of BaTiO 3 ), the increased rate of the dielectric constant of ECFs started decreasing. This was due to the fact that BaTiO 3 powder undergoes a phase transition from a tetragonal to a cubic structure, and its dielectric constant decreases at 130°C. The dielectric constant of BaTiO 3 powder was obtained from measured dielectric constants of ECF and application of the Lichtenecker logarithmic rule.