Electrically Isolated Hybrid Two-Phase Cooling System

Due to excellent properties of gallium nitride (GaN) high-electron mobility transistors (HEMTs), they are of great interest for high RF power applications in commercial and military markets.GaN HEMTs have an order of magnitude higher power density over silicon and gallium arsenide transistors, allowing a ten-time size reduction for the same output power, while simultaneously saving material cost.However, despite demonstrated high power-density above 40 W/mm (power per mm of the gate width of the device), commercial GaN HEMTs operate at much lower power densities up to 7 W/mm.This is due to the self-heating effect, which leads to formation of hotspots near the junction region of these devices, and results in a significant reduction in the lifetime and reliability of the power devices.Therefore, effective thermal management of high RF power systems using GaN HEMTs is crucial to ensure their high performance, reliability, and further commercialization.To address this issue, Advanced Cooling Technologies, Inc.(ACT) developed a two-phase cold plate design that allows the HEMTs to be directly mounted to the cooling surface.Using the latent heat of vaporization, high heat fluxes, such as those encountered by HEMTs, can easily be managed.In Phase I, ACT demonstrated a cold plate capable of removing heat loads well above 40 W/mm while also providing isothermality between heat sources.In Phase II, ACT intends to expand on this success by developing Coefficient of Thermal Expansion (CTE) matched cold plates for a few select applications, including government research and commercial power systems.Should the project be successful, higher power density electronics become a possibility, which would benefit multiple commercial, military, and research markets.