Theoretical investigation of sub-ambient on-chip microprocessor cooling

Thermal management of microprocessors is a continuing challenge for electronics package design. Traditional thermal management strategies have focused merely on maintaining the junction temperature just below the maximum permissible limit. This work investigates the feasibility of sub-ambient microprocessor operation using an appropriate cooling technology. A simple model for the temperature dependence of various sources of power dissipation and performance parameters of a microprocessor shows significant power and performance improvement due to sub-ambient operation. It is further shown that the total system power consumption, including the power required for microprocessor cooling may decrease for operation in a specific temperature window. Below a threshold temperature, the total power consumption exceeds current values due to the rapid rise in cooling power. Operation at temperatures lower than the critical value may still be attractive for applications where performance improvement is critical. Stirling cycle-based pulse tube cooling technology offers a low cost, high power efficiency solution to facilitate low temperature microprocessor operation. First-order thermodynamic calculations presented in this work show that it may be possible to use pulse tube coolers to remove heat loads expected in typical microprocessor operation