Design, Microfabrication and Thermal Characterization of the Hotspot Cooler Testbed for Convective Boiling Experiments in Extreme-micro-gap with Integrated Micropin-fins and Great Loss Minimization

Citation: 
Zhang, X., Nasr, M. H., Woodrum, D. C., Green, C. E., Kotke, P. A., Sarvey, T. E., Joshi, Y. K., Sitaraman, S. K., Fedorov, A. G., Bakir, M., “Design, Microfabrication and Thermal Characterization of the Hotspot Cooler Testbed for Convective Boiling Experiments in Extreme-micro-gap with Integrated Micropin-fins and Great Loss Minimization,” ITHERM 2016 The Intersociety Conference on Thermal and Thermomechanical Phenomena in Electronic Systems, May-June 2016, Las Vegas, NV.
Abstract: 
In this work, we designed, fabricated and characterized a novel hotspot testbed to dissipate ultra-high power density by two-phase convective boiling of refrigerant in a microgap with integrated micropin-fins and isolation air trenches around resistance heaters. The 300 μm long, 200 μm wide, and 10 μm tall microgap with 4 μm diameter micropin-fins was batch micro-fabricated in silicon. The 40 μm wide and 180 μm deep isolation air trenches around the heater and a SiO2 passivation layer were used to provide thermal isolation. The testbed dissipates a power density of up to 4.75 kW/cm2 using R134a refrigerant as the coolant. Thermal resistance and pumping power were compared between the micropin-fin device of interest and a reference ‘empty microgap’ device to assess tradeoffs in performance. Micropin-fins were found to slightly reduce thermal resistance at the cost of a large increase in pumping power. In addition to experimental work, thermomechanical simulations were implemented to analyze the reliability of the device for high pressure conditions.
Link to Paper: 
http://www.bakirlab.gatech.edu/papers/Design,%20microfabrication%20and%20thermal%20characterization%20of%20the%20hotspot%20cooler%20testbed%20for%20convective%20boiling%20experiments%20in%20extreme-micro-gap%20with%20integrated%20micropin-fins%20and%20heat%20Loss%20minimization.pdf