The Dielectric Behaviour of High Dielectric Permittivity Polymer-Matrix Composites

The development of satellite telecommunication technology have led to look for high permittivity-low weight organic materials for high frequency substrate and packaging applications. Mixtures of polymers and fillers were tested on their dielectric properties over a wide frequency range (from 10kHz to 20GHz). By loading a low dielectric loss polymer with titanate ceramic particles, the resultant composite shows high permittivity (9-10) and low dielectric losses (lower than 5 × 10¿3). If the polymer matrix composite is fabricated by filling with glass microballoons, the characteristic dielectric behaviour of the polymer remains. On the other hand, the addition of metal particles or semiconducting fibers to form the composite dramatically increases both the permittivity and the dielectric loss at gigahertz frequencies. Observable low frequency losses could be explained as the blocking effect of charge particles by an insulator phase, while the polarization process ocurring at high frequencies could be related to ionic or charge movements between equivalent positions at interfaces.