Study on the properties of the epoxy-matrix composites filled with thermally conductive AlN and BN ceramic particles

To develop new composites with sufficiently high thermal conductivity and suitably controlled Dkvalue for PCBs application, the composites were prepared from epoxy and AlN or BN fillers, and the effects of content, size, size distribution, and morphology of two fillers on the thermal and dielectric properties of the composites were investigated. The results showed that either AlN or BN fillers can greatly increase Tgand thermal conductivity, decreasing CTE and Df, and suitably controlling the increase of Dk. At the same filler content, BN-filled composites exhibit better thermal performance and dielectric properties compared to AlN-filled composites. In the case of BN-filled composites, it is found that plateletshaped micro-BN filled composite has lower Tgand higher CTE compared with particle-shaped nano-BN filled composite, but its thermal conductivity is remarkably higher than that of nano-BN filled composite. When hybrid BN fillers are used, thermal conductivity further increases. For micro-or nano-BN filled composite, the composite shows decreased Tgand increased Dkat high fraction of BN, but hybrid BN-filled composite still has high Tgand similar Dkwith epoxy even if at high fraction of BN. Compared with single-sized AlN-filled composite, it is found that hybrid-sized AlN-filled composite has higher Tgand lower CTE, but has lower thermal conductivity. To predict thermal conductivity and Dkin the investigated materials system, different models reported in the literature were analyzed and compared with the experimental data. Finally, suitable models were recommended.