CONTROL OF INCIPIENCE HYSTERESIS EFFECTS IN LIQUID COOLED ELECTRONICS HEAT SINKS

Abstract

Although air cooling continues to be the primary cooling technique for electronics, increases in chip density and power dissipation drive the need to study techniques such as liquid immersion cooling. This paper describes a saturated pool boiling study of interactions between different heat sources, located in close proximity so as to simulate neighboring ICs on a vertically oriented silicon multichip module, immersed in FC-72. The heat sinks tested consisted of re-entrant cavities etched in silicon to enhance thermal performance, while the heat sources were in the form of serpentine thin film heaters. The benchmark case to which all multiple heater tests were compared was the isolated central heater case with no heat dissipating neighbors. With just this heat source activated, the usual boiling incipience temperature hysteresis was experienced during the first increasing heat cycle. During the second cycle of increasing heat flux, this hysteresis all but disappeared, proving the efficacy of re-entrant cavities in trapping vapor, as long as the pool remained saturated. The presence of a neighboring heat source located below the test heater, dramatically improves the thermal performance, virtually eliminating hysteresis effects altogether.