Cooling the Electronic Brain

Abstract

This article discusses findings of some immersion cooling studies carried out to define the potential of direct liquid cooling of three-dimensional chip stacks. Four possible immersion cooling strategies were assessed. These included two active cooling strategies and two passive cooling strategies. The cooling densities for all four immersion cooling techniques were determined assuming the use of Fluorinert FC-72, a commonly used perfluorinated dielectric liquid. For passive systems, the cooling densities ranged from 25 W/cm3 for natural convection to 200–400 W/cm3 for pool boiling. For active technologies, the densities were 100–300 W/cm3 for forced convection and more than 2000 W/cm3 for flow boiling. It was found that the optimum die spacings for both single- and two-phase direct cooling was in the range of 0.2–0.6 mm for typical microelectronics geometries, though substantial cooling densities could be achieved at less-than-optimum spacings.