Effect of thermal conductivity on tracking failure of epoxy/BN composite under pulse strength

Epoxy resin (EX) is widely used for insulation in electric devices, but it has a relatively low thermal conductivity. One approach to obtain a higher thermal conductivity is to introduce inorganic fillers which have high thermal conductivity. Tracking failure is a thermal breakdown phenomenon which has a close relation with the thermal accumulation. In this paper, epoxy samples with boron nitride (BN) particles were prepared with different weight ratios. In order to investigate the relationship between thermal accumulation and tracking failure process, the resistance to tracking and tracking process were measured by infrared thermal imager from the front and back side with variation of different concentration of BN and different frequencies of pulse discharge. 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 the thermal accumulation. The improvement of thermal conduction plays an important role in the results of tracking failure. High frequency discharges are more easily 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.