Design and Testing of a Carbon Foam Based Supercooler for High Heat Flux Cooling in Optoelectronic Packages

The feasibility of using carbon foam as a heat sink and heat spreader in optoelectronic packages is assessed. A “supercooler” is designed, fabricated and tested to verify its cooling capability under high heat flux conditions in a typical optoelectronic package. The supercooler uses carbon foam as a primary heat transfer material. Water is soaked into the carbon foam and under evacuated pressure, boiling is initiated under the heating region to provide enhanced cooling. Experiments were conducted for a heat flux of up to 400 W/cm² deposited over a heating area of 0.5 mm × 5 mm. Two dimensional transient temperature distributions were recorded using a high speed infrared camera. Data were obtained for steady heating, as well as periodic heating with frequency up to 8 hz. Results show that the supercooler is very efficient in dissipating heat away from the heating region. Data obtained under 8 hz periodic heating with a peak power input of 10W, for example, showed that the temperature of the heated surface rises quickly to a local maximum of 15 to 20 °K above the ambient. The heated surface is then cooled uniformly back to a near ambient condition (with a maximum temperature of less than 5 °K above ambient) during the cooling half of the cycle (less than 0.0625 sec after the heating is turned off). The average cooling rate during the cooling period exceeds 170 °K/s. A numerical model, based on COMSOL, is developed to interpret the experimental data and to provide insights on the relevant physics responsible for the rapid cooling. Numerical data are presented to demonstrate how the supercooler can be further improved and adopted for other applications.