Spherical boron nitride/silicone rubber composite with high isotropic thermal conductivity via pre-constructing thermally conductive networks

Thermal interface material (TIM) is crucial for electronic devices to dissipate heat, but the high interface thermal resistance between polymer matrix and filler is a major problem affecting its thermal conductivity (TC). In this study, we prebuilt excellent thermally conductive pathway of isotropic spherical boron nitride (sBN) using a facile method, that is, pressing fillers, to decrease the interface thermal resistance before filling matrix silicon rubber (SR), and prepared a TIM with high isotropic TC. At 50 wt% filler content, the through-plane and in-plane TCs of sBN/SR composite reached 9.36 and 7.82 W/(m·K), respectively, which are higher than the highest value of previous research on bulk BN/SR composites (not including film), 4.13 and 6.56 W/(m·K), respectively. Meanwhile, the thermal decomposition temperature of TIM is 47.2°C higher than that of pure SR. In addition, the TIM has a low hardness (shore A hardness <70) and can be bent and folded, so can be used to substitute traditional thermally conductive silicone pad.