An investigation of fundamental factors influencing the permittivity of composite for embedded capacitor

The effect of the polymer permittivity on the permittivity of the polymer / lead magnesium niobate-lead titanate (PMN-PT) composite was investigated using epoxies, polyimides, polycarboxylic acids and PMMA. The permittivity of the polymers (without ceramic loading) ranged from 2.8 to 4.6. The permittivity of the composites was found to agree with the values predicted by the Lichtenecker and Smith equations except for epoxies. Polyacrylic acid (PAA) was found to be present on PMN-PT due to an acid-base neutralization reaction. Novolac epoxy was not found on PMN-PT. Because of the neutralization reaction, polycarboxylic acids could act as a surfactant to deaggromelate PMN-PT powder while epoxies may not. An electrostatic field simulation showed that the finer the particle size, the higher the permittivity of composite. These results could account for the lower permittivity of composites using epoxies than those of other polymers.