Current and future miniature refrigeration cooling technologies for high power microelectronics

Utilizing refrigeration may provide the only means by which future high-performance electronic chips can be maintained below predicted maximum temperature limits. Widespread application of refrigeration in electronic packaging will remain limited, until the refrigerators can be made sufficiently small so that they can be easily incorporated within the packaging. A review of existing microscale and mesoscale refrigeration systems revealed that only thermoelectric coolers (TECs) are now commercially available in small sizes. However, existing TECs are limited by their maximum cooling power and low efficiencies. A simple model was constructed to analyze the performance of both existing and predicted future TECs, in an electronic packaging environment. Comparison with the cooling provided by an existing high-performance fan shows that they are most effective for heat loads less than approximately 100 W, but that for higher heat loads, fan air cooling actually yields a lower junction temperature. If the efficiency of future TECs, as characterized by ZT_room, where Z is the figure of merit and T_room is room temperature, can be increased from the present value of ∼ 0.8 to 2 or even 3, the performance of the TEC improves dramatically, thus making them competitive for many electronic applications. Finally, one unanticipated result of the model was the realization that the thermal resistance between the refrigerator and the chip is not as critical as the thermal resistance between the refrigerator and the ambient air.