Laser-Tuned Surface Wettability Modification and Incorporation of Aluminum Nitride (AlN) Ceramics in Thermal Management Devices

Abstract

Aluminum nitride (AlN), a versatile ceramic with high thermal conductivity, high electrical resistivity, and a coefficient of thermal expansion compatible with silicon, is well-suited for direct-to-chip cooling applications of electronics, implementation in wide bandgap semiconductors, and for high-temperature heat exchangers. Despite multiple advantages, AlN's implementation in liquid-cooling applications is often hindered by surface-degrading effects of working-fluid-induced hydrolysis. Herein, a scalable -but highly tunable- wettability engineering approach is introduced, that allows effective implementation of bulk AlN substrates in enhanced two-phase cooling of electronics. The approach prevents hydrolysis of AlN by aqueous media and establishes control over surface roughness, all the while maintaining bulk integrity and material properties of the underlying substrate. Demonstration of the new approach is presented in spontaneous, pumpless, surface liquid transport, a necessity if such ceramics are to play an integral role as components of sealed, phase-change, wickless thermal-management devices (e.g., vapor chambers or heat pipes) that require rapid working-fluid transport in their multi-phase interior. The novelty of this work lies in establishing a scalable methodology for utilizing and further enhancing the properties of this non-oxide ceramic material for phase-change heat-transfer hermetic devices, thereby paving the way toward the implementation of this intriguing material in next-generation heat spreaders.