ADVANCED COOLING TECHNOLOGIES INC — Department of Energy SBIR Phase I: 24a

Description

Radio frequency (RF) power devices using (GaN) high-electron mobility transistors (HEMTs) have revolutionized power electronic applications due to superior electrical performances enabled by the excellent material characteristics of GaN HEMTs. However, the increasing power densities demanded from RF devices have led to serious thermal management issues which limits the device lifetime. Current cooling technologies are not ideal for high RF power devices because they result in mechanical stress between the transistors and the cooling system, have limitations in removing large heat fluxes, lead to high pumping power, and result in flow instabilities and hotspots, by using diamond heat sinks, heat pipes, microchannel liquid cooling, and microchannel two-phase cooling, respectively. Advanced Cooling Technologies, Inc. (ACT) proposes an innovative Hybrid Two-Phase Cooling System (HTPCS) to remove large amounts of heat from transistors in high RF power devices. The cooling system is CTE-matched (CTE: coefficient of thermal expansion) and dielectric, and operates with the minimal flow rates and pumping power, and provides highly isothermal transistors. ACT proposes an innovative HTPCS that can remove a large amount of heat from transistors, and provide highly isothermal transistors (due to the nature of two-phase heat transfer mechanism). The cooling system is essentially a hybrid between a pumped two-phase cooling loop with capillary driven two-phase cooling. The capillary evaporation takes place from the evaporator wick structures, which are continuously supplied with liquid refrigerant by a pump. The proposed cooling system is CTE-matched, and dielectric. The working fluid is refrigerant due to its dielectric strength. The primary objective of the Phase I effort is to develop a prototype HTPCS and conduct the performance tests to demonstrate the capability of the cooling system to remove heat fluxes over 200 W/cm2 from individual transistors, and a total heat over 120 W from each substrate that includes four transistors in series. This task will be done by fabricating a copper-based cooling enclosure and conducting its performance tests. By the end of Phase I, the final CTE-matched cooling enclosure will be fabricated and its hermeticity will be checked. Also, a preliminary thermal modeling will be developed to characterize the thermal performance of the proposed cooling system.Commercial Applications and Other Benefits: A CTE-matched and highly efficient cooling system for the challenging RF power applications results in enhancing the reliability and the maximum power output of RF devices, and allows for wider adoption of RF devices in a broad range of applications such as wireless communications, data centers, renewable energy, electric vehicles, etc.