Spray cooling thermal management for increased device reliability

A study has been conducted to quantify the ability of spray cooling to handle transient die power dissipation, as well as to quantify its effect on device reliability. The transient study was conducted with a bare die thermal test vehicle, while the device reliability studies were conducted with a dual Opteron Compact PCI single board computer. For the transient response studies, the high heat transfer coefficients associated with the spray cooling enabled the die to transition from one steady-state point to another in under 2 seconds, when cycling the power delivered to the die between 0 and 94 W. For the device reliability studies, an air-cooled version of the server board was compared to a spray cooled version, for the same clock frequency and supply voltages. For identical conditions, the spray cooled microprocessor processor diode temperature was 33.3°C lower, and the die dissipated 35% less power. The paper will present an analysis that explains the manner in which modern microprocessors operate, and will explain the reason for the higher power dissipation associated with the hotter microprocessor.