Effect of Diamond Morphology on Construction of Thermal Conduction Path in Flexible Thermal Interface Materials

The increasing demand for chip heat dissipation has led to more challenges in designing and regulating thermal interface materials with high performance. It is crucial to have a comprehensive understanding of the design and mechanism of thermal conduction path built by thermal conductive fillers. Diamond, in particular, has garnered significant attention. In this study, we constructed three-dimensional particle random distribution models of diamond/silicone rubber composites based on the morphological characteristics of common industrial-grade diamond. We also conducted experiments with different morphologies and filling amounts of diamonds in silicone rubber to better understand the effect of diamond fillers on the thermal conductivity of the composites. From the model simulation, thermal conductivity and actual LED temperature rise tests, the study reveals that broken single-crystal diamond with lamellae or rod-like with large aspect ratio or radius-thickness ratio is easier to form thermal transfer paths than spherical or spherical-like diamond under low filling content. Ultimately, the silicone rubber composites filled with intact hexa-octahedral single-crystal diamonds achieve the highest thermal conductivity as a result of the formation of more comprehensive three-dimensional heat dissipation network (1.357 W/(m K), 80 wt.%). In comparison with silicone rubber composites filled with spherical Al₂O₃ (0.995 W/(m K), 80wt.%) and pure silicone rubber (0.21 W/(m K), 80 wt.%), the thermal conductivity increases by 36% and 546%, respectively. The revelation of the construction law and mechanism of different diamond morphologies on the thermal conduction path of thermal interface materials provides a theoretical basis for broadening the application of diamond in the design of thermal interface materials.