Numerical Investigation of Silicon-Embedded Microchannel Structures Containing Different Shaped Interior Flow-Splitting Walls and Micro Pin-Fins for Hotspot Mitigation of GaN High-Power Devices

The significance of cutting-edge thermal management technologies has been growing apace as a continuing trend in miniaturization of the gallium nitride-based wide band-gap devices poses major challenges in heat extraction. Bringing the coolant in close proximity to gate fingers is a promising method to handle concentrated heat in a small footprint. Therefore, the implementation of die-embedded microfluidic structures may substantially enhance hotspot mitigation. To prevent such devices from overheating, a variety of die-embedded microfluidic cooling structures with interior flow-splitting walls and different combinations of micro pin-fins and sidewall ribs are proposed. Proposed microfluidic structures are benchmarked for the operating condition where the heat flux of each gate finger is approximately 18 kilowatts per square centimeter. Results indicate that microchannels with straight interior flow-splitting walls offer more than two times higher local Nusselt numbers than traditional straight microchannel heat sinks. Furthermore, compared to microchannels with straight interior walls, integration of wavy interior flow-splitting walls inside substrate-embedded microfluidic structures may provide up to 43% improvement in local Nusselt numbers at high Reynolds numbers. Nevertheless, it should also be considered that wavy details increase friction factor accompanied by pressure drop due to hindered fluid flow. Moreover, based on the operating conditions in this study, elliptical micro pin-fin structures outperform their circular and diamond-shaped counterparts in overall performance. The findings presented in this paper will be particularly beneficial for researchers aiming to employ suitable microfluidic structures for hotspot mitigation.