Hotspot Thermal Management With Flow Boiling of Refrigerant in Ultrasmall Microgaps

As integration levels increase in next generation electronics, high power density devices become more susceptible to hotspot formation, which often imposes a thermal limitation on performance. Flow boiling of R134a in two microgap heat sink configurations was investigated as a solution for hotspot thermal management: a bare microgap and inline micro-pin fin populated microgap, both with 10 μm gap height, were tested in terms of their ability to dissipate heat fluxes approaching 5 kW/cm² at the heat source. Additional parameters investigated include mass fluxes up to 3000 kg/m² s at inlet pressures up to 1.5 MPa and exit qualities approaching unity. The microgap testbeds investigated consist of a silicon layer which is heated from the bottom using resistive heaters and capped with glass to enable visual observation of two-phase flow regimes. Wall temperature, device thermal resistance, and pressure drop results are presented and mapped to the dominant flow regimes that were observed in the microgap.