A uniform temperature, ultra high heat flux liquid cooled, power semiconductor package

A new type of heat exchange process is described for use in semiconductor heat sinks. It involves the use of subcooled, nucleate boiling at concave curved surfaces where radial acceleration, v/sup 2//r, can be used to develop significant and beneficial buoyancy forces. The system provides a heat transfer surface with a uniform temperature, i.e. the boiling point of the fluid, and requires no vapor-liquid separation process since all vapor bubbles are immediately condensed in the subcooled liquid, Use of low-boiling-point dielectric fluids, e.g., FC 72 (BP 56 degrees C), establishes a uniform heat sink temperature that is independent of location or environment and does not require elaborate coolant and/or environmental conditioning. The low junction-to-fluid specific thermal resistance, approximately 0.1 degrees C/W-cm/sup 2/, and high heat flux dissipation capability, approximately 6000 W/cm/sup 2/, inherent in this design lend themselves to a system design with high reliability and lower manufacturing costs. Failure rates are reduced and leakage currents are lowered by virtue of lower device operating temperatures resulting from the low-boiling-point coolants. The design lends itself to compact, lightweight construction for high-voltage series operation of devices and permits simplified parallel operation of high-power devices. Experimental studies have demonstrated a heat flux of 6300 W/cm/sup 2/ using FC 77 with a pressure drop of only 2.70 lb/in/sup 2/ over a 1 cm-long heat transfer channel.<
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