Proportional Optimization Model of Multiscale Spherical BN for Enhancing Thermal Conductivity

The power electronics tend to become miniaturized and multifunctionalized, such as thermal rotators, circuit breakers, and microchips, which have necessitated creating instruments for investigating thermal mechanisms and enhancing thermal conductivity. In this paper, we construct the heat flow network of spherical boron nitride (BN) and used multiscale spherical BN to improve the thermal conductivity of the composite synergistically. The multiscale spherical filler ratio optimization model based on the Dinger–Funk particle stacking theory is established, which obtained the optimal volume ratio of 0.224:0.374:0.402 with D50 of 20, 70, and 160 μm. Meanwhile, the effects of multiscale filler ratio, morphology, filler content, and temperature are investigated. The thermal conductivity of composites can reach up to 1.84 W/(m·K) at 20 vol %. Significantly, the thermal conductivity of composites is 4.82 W/(m·K) at 30 vol %, which is achieved by optimizing the multiscale filler and particle size distribution.