Gas Assisted Thin-Film Evaporation for Hotspot Thermal Management

Presence of hotspots in microprocessors requires localized dissipation of high heat fluxes. While typical background cooling solutions (e.g. air cooling with heat sinks/spreaders, heat pipes etc.) fail to address hotspots, aggressive fluidic cooling with liquid to vapor phase change can potentially meet this goal. In particular, we have been successful in cooling hotspots with a micro-fabricated device providing evaporative cooling. Fundamentally different from boiling, the device takes advantage of evaporation from the free surface of a very thin film of coolant enhanced by flow of dry sweeping gas. Heat transfer coefficients close to 0.1 MW/m²K have already been demonstrated exceeding the performance of other contemporary phase change cooling solutions. This development can potentially play a very important role in designing effective thermal solutions for next generation microprocessors, with application in 3D stacked chips, cooling on-chip optical devices and power electronics, among others. In this paper, we briefly describe the various components constituting the device and the experimental procedure employed for testing the device under different operation conditions. In particular, we investigate the effect of flow configuration of the sweep gas on the overall performance of the system. Jet impingement of air is characterized by varying two operating parameters: (1) the separation between the jet’s nozzle and the evaporation surface, and (2) the inclination of the jet with respect to the evaporation surface (i.e., oblique jet impingement). The results from these experiments help elucidate the importance of these two factors in determining the overall performance of the device.