Thermoformable Boron Nitride Based All‐Ceramics

• Published in: Advanced materials (Weinheim) Vol. 34; no. 42; pp. e2203939 - n/a
• Main Authors: Bice, Jason E., St. Germain, Echo, Wohlever, Samuel J., Goddard, Grace, Erb, Randall M.
• Format: Journal Article
• Language: English
• Published: Weinheim Wiley Subscription Services, Inc 01.10.2022
• Subjects: Boron nitride; boron‐based ceramics; ceramic matrix composites; Ceramics; Circuit boards; Heat sinks; Materials science; Microstructure; phononic heat transfer; Photopolymerization; Preforms; Pressure molding; Sheets; Sintering; Thermal management; Thermoforming; Workflow
• ISSN: 0935-9648; 1521-4095
• DOI: 10.1002/adma.202203939

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. Electrically insulating thermoformable ceramic matrix composites, for low‐profile thermal management, take advantage of phononic conducting networks to transport heat from the heat source. This advancement and new field of study outlined in this work, show significant promise to enable size reduction and effective cooling advantage over the incumbent aluminum metal heat sinks.