Hotspot Thermal Management via Thin-Film Evaporation—Part I: Experimental Characterization

Abstract

The presence of hotspots with extreme heat fluxes and temperatures in high-performance electronics has led to severe thermal management challenges in the semiconductor industry. Our work experimentally investigates the potential of capillary-fed thin-film evaporation as a thermal management solution for devices where hotspots are superposed with mild background heating. The front side of our test device incorporates well-defined silicon micropillar arrays for passive fluidic transport via capillary wicking, and the backside is patterned with thin-film resistive heaters to emulate $640 \times 620~\mu \text{m}^{2}$ hotspots and $1 \times 1$ cm2 uniform background heating. Our micropillar wick design facilitates efficient fluidic and thermal transport and dissipated ${\approx} 6$ kW/cm2 from a single hotspot without background heating beyond which viscous losses exceeded the capillary pressure and dryout occurred due to insufficient liquid supply. While the capillary-limited hotspot dryout heat flux decreased by creating concurrent hotspots as well as by superposing a hotspot with mild uniform background heating, it was unaltered (within the measurement error) when the location of the hotspot was varied within the $1 \times 1$ cm2 microstructured area. The ultrahigh heat fluxes in our experiments were achieved by suppressing boiling by judiciously designing the fluidic transport where the microstructured surface maintains a thin liquid film and syphons only the required amount of liquid to sustain evaporation. Our experimental results show that thin-film evaporation is a viable thermal management solution for the next-generation high-performance power electronics, among others, where hotspots pose a significant challenge.