Hexagonal boron nitride (BN) is often used as filler to improve the thermal conductivity of polymer matrix due to its high thermal conductivity. However, previously reported BN-based composites always have a high in-plane thermal conductivity, which is not beneficial for vertical heat dissipation. In addition, high BN content results in the deterioration of the mechanical properties. Here, we report a feasible method to prepare a BN/silicone rubber (SiR) composite with oriented BN in organosilicon matrix via a vacuum-assisted self-assembly technique. The BN/SiR composite displays a 1270% higher (2.74 W/(m·K)) thermal conductivity than that of neat organosilicon matrix (0.20 W/(m·K)). The oriented BN nanosheets increase the polymer's adhesive force and exhibit excellent compression cycle performance. In turn, these features support its superiority as thermal interface material in the light-emitting diode chips heat dissipation application.

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With the miniaturization of electronic devices and the development of integrated circuit chips in higher density and higher frequencies, thermal management has become one of the most critical challenges in device performance and reliability. Thermal interface material is bonded between the chip and heat sink. In addition to its thermal conductivity, the mechanical property is essential. Good resilience can effectively fill the bonding gap and reduce thermal resistance, thus improve the overall thermal conductivity. In this paper, three methods are adopted to prepare BN nanosheets/polymer composites. Two polymer composites materials with BN nanosheets oriented were prepared through different suction filtration methods, and the process of homogenization and mixing prepared another sample. Then the microscopic appearance structure of the three materials was analyzed by scanning electron microscope(SEM). The anisotropic compression resilience and tensile properties were studied, respectively. The study showed that BN nanosheet-oriented materials have anisotropic mechanical properties. The better the orientation performance, the greater the difference in the anisotropic mechanical properties of the composite materials. Under the pressure of 0.08MPa, materials with better BN nanosheet orientation have excellent compression and resilience performance, but homogeneous composite materials have the best compression resilience performance. The tensile properties of the three composite materials are quite different. The tensile strength of the homogeneously composite materials can reach 119.59%, while the in-plane and through-plane tensile strength of the other two materials can reach 102.84%,38.52%, and 67.65%, 46.67%, respectively.@en