Thermal and mechanical properties of epoxy composites with a binary particle filler system consisting of aggregated and whisker type boron nitride particles

This study aims to investigate packaging materials based on polymer matrices for microelectronics. A binary filler system consisting of whiskers and aggregated particles of boron nitride (BN) was employed to improve the thermal conductivity of the epoxy resin. To prevent filler breakage during commercial mechanical mixing, a wetting method was used during sample fabrication. The polar functionalities introduced on the BN particles by sodium hydroxide treatment allowed the permeation of the epoxy resin because of a secondary interaction, which allowed the fabrication of a composite without voids. The maximized filler packing density and filler dispersion of the two kinds of fillers caused changes in the thermal conductivity. According to our results, the composite containing a 70:30 volume percent of the filler fraction of aggregated and whisker-type BN particles showed the maximum thermal conductivity. This is ascribed to the maximized formation of conductive networks combined with minimization of the heat resistance along the heat flow path. The filler composition and shape also resulted in composites with a higher storage modulus.