Immersion cooling module for military COTS applications

Thermal management needs of the electronics industry continue to be driven by the demand for increased functionality, high heat dissipation and density, component miniaturization, and the reliability benefits of junction temperature reduction and control. In military/aerospace applications, these challenges are exacerbated by harsh environment considerations (e.g. extreme temperatures, shock and vibration, humidity, corrosive surroundings, orientation variations), open standards form factors with defined physical envelopes, and increasing pressure to employ commercial-off-the-shelf (COTS) hardware. Clearly, there exists a need to explore and develop advanced cooling technologies that can meet the anticipated requirements of future military electronic systems. As a means to this goal, card-level passive immersion cooling experiments were performed with gas-saturated FC-72, FC-77, and FC-84 over a range of system pressures to characterize the heat dissipation performance of a VME-size laboratory prototype (233×160×18 mm). Chip heat fluxes in excess of 20 W/cm² were achieved while maintaining chip temperatures below 110°C. Further, an overall module heat dissipation of 124 W was transferred with 80°C module edge temperatures. The thermal performance of the module was limited by the presence of a vapor/air gap and was improved by increased system pressure. Results suggest that FC-84 at 1.5 atm may provide an acceptable compromise between operating pressure, vapor/air space growth, and boiling critical heat flux (CHF) limitations.