Thermal accumulation and tracking failure process of BN-filler epoxy-matrix composite

Epoxy Resin is widely used for insulation in electric devices, in spite of its weak ability of thermal conduction. One approach to obtain a higher thermal conductivity is to introduce inorganic fillers which have high thermal conductivity. The purpose of this paper is to study the effect of boron nitride (BN) particles on thermal breakdown tracking process. In this paper, epoxy samples with BN particles were prepared with different weight ratios. In order to investigate the relationship between thermal accumulation and tracking failure process, tracking failure process under different frequency of pulse discharge was investigated by an infrared thermal imager from the front and back side. Obtained results showed that with increasing the concentration of BN particles, the time to tracking failure increased. The added BN fillers have a very significant inhibitory effect on thermal accumulation. The improvement of thermal conduction plays an important role in the results of tracking failure. High frequency discharges are more likely to cause the thermal accumulation, which is unfavorable to the reliability of materials. It is concluded that the tracking failure performance could be improved by reducing the thermal accumulation.