Thermal Conductivity and Dielectric Properties of Epoxy Composites Co-doped with BN with Different Morphology

Electronic devices are developing towards high voltage, high power, miniaturization and integration. As an insulating packaging material—epoxy resin, higher requirements are put forward for its thermal conductivity and dielectric properties. In this paper, BN with excellent insulation performance and thermal conductivity is selected as the inorganic filler, and the effects of nano-hexagonal BN (h-BN) single doping and nano-hexagonal BN co-doping with micron-BN whisker (w-BN) on EP performance are comparatively studied. It is found that the dielectric constant of the high content h-BN/w-BN/EP composites is higher than h-BN/EP composites. The dielectric loss of h-BN/EP is lower than EP at $10^{0}-10^{6}$ Hz. The dielectric loss of h-BN/w-BN/EP is higher than that of pure EP at $10^{0}-10^{3}$ Hz, and lower than pure EP at $10^{3}-10^{6}$ Hz. The addition of h-BN and h-BN/w-BN will reduce the breakdown field strength of the composites. With the content of h-BN increases, the breakdown field strength of h-BN/EP decreases first and then increases. The breakdown field strength of h-BN/w-BN/EP composites decreases gradually with the content increasing, and the breakdown field strength of pure EP is 198.5 kV/mm, while the breakdown field strength of 30 wt.% h-BN/w-BN/EP composites is 89.43 kV/mm, which is 45.05 % of the pure EP. The introduction of h-BN, h-BN/w-BN can increase the glass transition temperature of epoxy resin. The h-BN and h-BN/w-BN can effectively increase the thermal conductivity of EP, and h-BN/w-BN enhance more obviously. The 30 wt.% h-BN/w-BN/EP composites have a thermal conductivity of 0.351 W/(m·K), which is 206 % of pure EP.