THERMAL PERFORMANCE OF AN INTEGRAL IMMERSION COOLED MULTICHIP-MODULE PACKAGE

A multichip module (MCM) package was constructed that uses integral im mersion cooling to transfer heat from the chips to a final heat transf er medium outside the package. The package is a miniature immersion co oled system with a pin-fin condenser that can be operated in either th e submerged or vapor-space condensing mode. Sixteen chips were bonded on a 57-mm-square alumina substrate carrying copper/polyimide thin-fil m interconnect. Tests of the thermal performance of the system show th at it is capable of handling over 160 W power with chip thermal resist ances, based on chip area, as low as 2 K-cm2/watt provided by the imme rsion cooled portion of the thermal path. Tests have been performed wi th 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 rangi ng from 20-degrees-C to 50-degrees-C were used to obtain a performance map delineating the heat transfer regimes in the module and the limit s imposed by critical heat flux and condenser performance. The fluid u sed in the module enclosure was Fluorinert FC72.