Preparation and characterization of epoxy-based composite with multilayered structure and high thermal conductivity

A multilayered thermally conductive composite with ternary system of heat conductive fillers-thermally conductive films-epoxy matrix was prepared through a facile process of layer-by-layer stacking, pre-curing and hot-pressing. The thermally conductive films (boron nitride nanosheets/cellulose nanofiber) with high in-plane thermal conductivities were employed as the heat conductive medium, while the platelet-shaped hexagonal boron nitride and the particle-shaped aluminum nitride were utilized as heat conductive fillers for enhancing the perfection of the thermally conductive network. A horizontally heat conductive network was constructed within the epoxy matrix under the joint contribution of the horizontally aligned hexagonal boron nitride platelets and the parallelly spread thermally conductive films through hot-pressing. The aluminum nitride particles acted as linking points, filling the gaps between hexagonal boron nitride platelets, while constructing the thermally conductive path in the vertical direction. Thanks to the introduction of thermally conductive films and the good orientation of boron nitride platelets, the in-plane thermal conductivities of the composites increased with increasing of film layer number. With film layer number of 9, and filler content of 30 wt% (aluminum nitride/boron nitride (1:1)), the in-plane thermal conductivity of the composite was as high as 8.53 W m−1 * K, which showed an enhancement of 4165% than that of the pure epoxy matrix, and an improvement of 613% compared to that of the composite without multilayered structure. Meanwhile, the out-of-plane thermal conductivity exhibited a slightly deceased tendency as film layer number increased, but it still reached 0.87 W m−1 * K with film layer number of 9, which was 335% higher than that of the pure epoxy. In addition, the multilayered composite also possessed good thermal stability, enhanced stiffness, as well as low dielectric constant and dielectric loss, which shows a potential application in thermal management for packaging of integrated circuit and microelectronic devices.