Temperature dependence of the dielectric properties of polymer composite based RF capacitors

Abstract

The temperature dependence of the dielectric properties of high Q polymer-based composites was discussed in terms of microstructural differences with various filler contents. Liquid coatable high Q polymer-based composites with 3–4× improvement in dielectric constant and precisely controlled temperature coefficient of capacitance (TCC) were developed with Ta2O5 as the inorganic filler. The base polymer showed a negative TCC of −250ppm/°C from room temperature to 125°C. Measurement of TCC with samples containing Ta2O5 greater than 30vol.% showed TCC of ±50ppm/°C with moderate capacitance density, whereas no detectable improvement in the TCC was observed in samples having 20vol.% Ta2O5. The electron micrographs of this low filler content sample gave a clear indication of clustering, i.e. particle agglomeration. The homogeneity of the particle distribution was more pronounced in the sample with 40vol.% Ta2O5.