Application of air cooled microchannel heat exchangers to card cage systems

An application of a novel-geometry, air-cooled, microchannel heat exchanger for electronic chips reported by C. Hilbert et al. (1990) is described. These heat exchangers, based on narrow channels and laminar flow, are scaled to cool large packets, mated to high-power pin grid arrays (PGAs) or multichip modules (MCMs), and mounted on printed circuit boards in a card cage. The heat exchanger reported fits within the package footprint and meets chip temperature specifications to 50 W. The system provides cooling for two MCM or PGA boards, each carrying eight 35-W modules using the scaled design. The modules were mounted on a printed wiring board, along with conventional components dissipating an additional 100 W. Chip temperature rises within the packages were kept to 50°C above ambient. The entire card cage contained the two MCM or PGA boards and several other conventionally cooled boards. Fan placement and air flow design were conventional except for the provision of ducting above the high-power packages. The heat exchangers operate at a very low pressure loss, allowing the MCM section to be cooled with two common axial flow fans while generating acoustic noise within the range acceptable for office equipment