Experimental study on the immersion cooling of an upward-facing multichip module with an opposing condensing surface

Experiments were conducted to study the heat transfer performance of a simulated immersion cooling module. The test section consisted of three upward-facing, P-doped silicon chips bonded on a substrate and a downward-facing, finned condenser. FC-72 was filled in a space formed between the substrate and the condenser. The effects of space height, cooling water temperature and fin spacing were examined. The wall superheat in the nucleate boiling region was considerably higher than those reported for a metal surface and silicon surfaces with a thin film resistor pattern. For a fin spacing of 0.65 mm, rise of bubbles was blocked by the fins of the condenser and the critical heat flux decreased with decreasing space height. For a fin spacing of 1.0 mm, bubbles rose through the fins and the heat transfer performance was not affected by the space height as long as it was 1.6 mm or greater. The heat flux increased with decreasing cooling water temperature. The increase was more significant for a low wall superheat region than for a high wall superheat region.