Enhanced dielectric properties and thermal stability of epoxy induced by polyhedral oligomeric silsesquioxanes

With the development of industrial technology, the power module has to suffer from high temperature, high voltage, and high frequency. Meanwhile the effect of temperature and space charge on dielectric properties is becoming more and more serious. The traditional epoxy cannot meet the requirements of high temperature and high insulation. In this work, polyhedral oligomeric silsesquioxanes (POSS) are introduced to epoxy to prepare composites with various filling ratios. The characterization results indicate that there is good compatibility in the POSS/epoxy system. When the filling content is 2.5%, the composite possesses the largest dipole relaxation activation energy value of 0.45 eV and has the lowest dielectric constant as well as dielectric loss. The trap energy and density of the composites are tested and calculated. Among the pure and composite samples, the deepest traps are introduced in the composites with 1% POSS. The composites have the similar tendency for the properties of DC breakdown strength, DC conductivity, and space charge dynamics. A trapregulated space charge behavior model is proposed to analyze the above properties. Significantly, the thermal stability and the glass transition temperature (Tg) are enhanced with the filling ratio, the char yield increases from 6.19 to 16.17%, and the Tg increases from 180 to 222 degrees C. Thus, a new kind of composite that has excellent dielectric properties and temperature stability is fabricated, which opens a novel window for the electronic packaging materials.