Exceptional Thermal Conductivity in Printed Dielectrics through Compositional and Microstructural Design

As electronic devices become simultaneously more powerful and compact, thermal management is increasingly critical. Optimizing components like heatsinks is increasingly required, which has recently leveraged additive manufacturing. There is growing demand to move away from incumbent metallic materials for dielectric materials that are electrically insulative and transparent to radio frequency signals. Thermally conductive polymer composites containing phonon-conducting ceramics offer a low-density dielectric solution compatible with fused filament fabrication. However, these materials have struggled to exceed thermal conductivities of 4 W m^-1 K^-1 due to challenging rheological flow effects at high filler volume fractions that prevent stable material extrusion. In this work, multi-generational compositional design is conducted to develop a printable low-loss dielectric composite that achieves over 16 W m^-1 K^-1, comparable to stainless steel. This breakthrough is enabled by thermal post-processing, which promote templated crystallization in a poly-lactic acid matrix from surface-modified boron nitride platelets, creating a "hetero-percolated network". The resulting material is three dimensionally printed into heatsinks that perform as effectively as metallic heatsinks while being electrically insulative and RF transparent.