Spherical and flake-like BN filled epoxy composites: morphological effect on the thermal conductivity, thermo-mechanical and dielectric properties

Epoxy composites, with boron nitride spheres (s-BN) and flakes (f-BN) as fillers were prepared. The effect of filler morphology, content, and crystallization of BN particles on the thermal conductivity, thermo-mechanical and dielectric properties of the composites were investigated. At the same loading level, s-BN with smaller size and larger surface area led to much more significant increase in the glass transition temperature ( T g ), reduction in the coefficient of thermal expansion and lower storage modulus ( E ′), while much higher thermal conductivities were observed in epoxy composites containing f-BN, owing to the larger aspect ratio and better crystallization. In addition, the introduction of BN fillers only did slightly increase on the dielectric constant and dielectric loss of the epoxy resin. We believe, the BN enhanced epoxy composites, with significantly improved thermal conductivity and thermo-mechanical properties, yet maintaining low dielectric constant and dielectric loss at the same time, have great application potential in the microelectronic insulation industry.