Thermoformable Boron Nitride Based All-Ceramics

Abstract

Thermoforming processing, traditionally reserved for thermoplastic polymers and sheet metals, is extended here to boron-based all-ceramics. Specifically, sintered boron nitride composite sheets manufactured via a combined vibration and tape-casting photopolymerization process exhibit a highly oriented microstructure that allows these preform sheets to flow as viscous Bingham pseudoplastics during compression molding. These sintered all-ceramic preforms are thermoformed into thin, complex parts with features down to 200 µm. Further, a new workflow is leveraged to generate bespoke all-ceramic heat spreaders that can be press-fit onto printed circuit boards and outperform metal heat sinks as a low-profile thermal management solution. This work offers a route for other all-ceramics that may be thermoformed through first fabricating pre-forms with highly-ordered anisotropic microstructures.