Microjet cooling devices for thermal management of electronics

This research is an effort to demonstrate the applicability of miniaturized synthetic jet (microjet) technology to the area of thermal management of microelectronic devices. Synthetic jets are jets which are formed from entrainment and expulsion of the fluid in which they are embedded. Design issues of microjet cooling devices are discussed along with characterization of excitation elements and the turbulent synthetic jets produced thereby. Geometrical parameters of the microjet cooling devices were empirically optimized with regards to cooling performance. The cooling performance of the optimized microjets was compared with previous theoretical and empirical studies of conventional jet impingement. The cooling performance of the microjet devices has been investigated in an open environment as well as in a vented and closed case environment. In such experiments, the synthetic jet impinges normal to the surface of a packaged thermal test die, comprising a heater and a diode-based temperature sensor. This test assembly allows simultaneous heat generation and temperature sensing of the package, thereby enabling assessment of the performance of the synthetic jet. Using microjet cooling devices, a thermal resistance of 30.1°C/W has been achieved (when unforced cooling is used, thermal resistance is 59.6°C/W) when the test chip is located at 15mm spacing from the jet exit plane. In order to more directly compare and scale the cooling results, a preliminary study on heat transfer correlations of the microjet cooling device has been performed. Finally, a comparison of the performance of the microjet cooler with standard cooling fans is given.