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

Abstract 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.