Synthesis of Boron Nitride Coated Silica Filler for Preparing Thermally Conductive Epoxy Composites

Increasing power density in the modern electronics with continuous miniaturization and rapid growth in functionality demands fast heat removal capability of the package from the chip. Traditional encapsulant materials such as epoxy molding compounds or underfills are seen as poor thermal conductor due to the low intrinsic thermal conductivity of the fused silica fillers (~1 W/mK) extensively used in formulating these epoxy encapsulants. Boron nitride (BN) possesses extraordinarily high thermal conductivity (~400 W/mK in plane) but its 2-D platelet shape limits the loading level due to the rheological issues. In this work, the BN coated silica (BN@SiO2) fillers are synthesized through silane assisted assembly method. The chemical modification on the filler interface chemistry and the morphology of the synthesized BN@SiO2 is discussed in detail. A significantly reduced viscosity at various shear rates demonstrates the better flowability of epoxy loaded with BN@SiO2 fillers compared to those directly mixed with BN and SiO2 fillers, indicating the potential of further increase of BN loading level. Moreover, the much-improved thermal conductivity in these composites (~0.7 W/mK at 30 wt% loading) suggests that the as synthesized BN@SiO2 could be promising candidate to prepare highly thermally conductive epoxy encapsulants in order to effectively dissipate the heat generated from high performance chips.