Particle Size‐Dependent Thermal and Electrical Behavior of h‐ <scp>BN</scp> /Epoxy Composites: From Nano to Micro Scale

ABSTRACT Efficient thermal management of electronic packaging materials is critical for high‐power‐density electronic systems. This study systematically investigates the influence of hexagonal boron nitride (h‐BN) filler particle size (50 nm–10 μm) on the thermal conductivity, dielectric properties, and processability of epoxy‐based composites. Quantitative results demonstrate that micron‐scale fillers (approximately 1 μm) achieve a synergistic optimization: thermal conductivity reaches 0.887 W m −1 K −1 at 25 wt% loading, the highest breakdown strength attains 84.23 kV/mm, and volume resistivity reaches 6.59 × 10 14 Ω m. In contrast, nanoscale fillers introduce phonon scattering centers and microdefects due to severe agglomeration, degrading both thermal and electrical insulation performance. Larger fillers (5–10 μm) exhibit limited performance enhancement because of poor interfacial compatibility and sedimentation. This study further reveals a competitive mechanism between “thermal pathway construction” and “interfacial insulation regulation” across different filler sizes, providing quantitative guidelines for particle size selection in the design of high‐performance thermally conductive insulating materials for electronic packaging.