Strategic Fabrication of Robust Spherical Hexagonal Boron Nitride Particles for Thermally Conductive Applications

Hexagonal boron nitride (h-BN) has a layered structure similar to graphite and thus exhibits excellent thermal stability, electrical insulation, and chemical and corrosion resistance, resulting in a material of choice in numerous applications. However, its unique layered structure of h-BN hinders the dense packing of h-BN flakes, which poses challenges in practical applications. In this study, we present a novel and practical approach for fabricating micrometer-sized spherical-shaped h-BN particles with enhanced strength. This strategy involves fusing h-BN flakes with h-BN synthetic precursors, a homogeneous material without heterogeneous additives. The precursor reacts between the aggregated particles to form new h-BN bonds that connect the h-BN flakes, which improves the bonding strength. The self-densification and fabrication of h-BN particles can be achieved with a significantly lower temperature of 1100 °C without any pressing process. The precursor additives strengthened the necking between the particles and filled the voids between the h-BN flakes. By appropriately controlling the precursor content, voids within the composite can be alleviated. This approach resulted in spherical particles without a secondary phase, preserving the properties of h-BN. This effective strategy opens up new application possibilities in ultrafine thermally conductive systems, including the latest semiconductor stack packaging or micro-LED devices.