Thermal performance of an integral immersion cooled multichip module package

A multichip module (MCM) package was constructed that uses integral immersion cooling to transfer heat from the chips to a final heat transfer medium outside the package. The package is a miniature immersion cooled system with a pin-fin condenser that can be operated in either the submerged or vapor-space condensing mode. Sixteen chips were bonded on a 57-mm-square alumina substrate carrying copper/polyimide thin-film interconnect. Tests of the thermal performance of the system show that it is capable of handling over 160 W power with chip thermal resistances, based on chip area, as low as 2 K-cm²/watt provided by the immersion cooled portion of the thermal path. Tests have been performed with the module fully powered and with subsets of the chips powered. The results indicate that the heat transfer coefficient is similar in all partially powered modes. Data taken with condenser temperatures ranging from 20°C to 50°C were used to obtain a performance map delineating the heat transfer regimes in the module and the limits imposed by critical heat flux and condenser performance. The fluid used in the module enclosure was Fluorinert FC72