부산대학교 도서관

High thermal dissipation power in new generation processors is excessively demanding for cooling systems. Immersion cooling using the phase-change of dielectric liquids is a viable candidate for electronic cooling. Porous coatings are one of the most efficient methods of increasing the boiling heat transfer and evacuating heat from electronic components under immersion cooling. We have developed a novel multi-scale electroplated porous (MuSEP) coating with a random pore size distribution across its surface that increases the boiling efficiency significantly. The coating is deposited at room temperature and can be added to off-the-shelf electronic parts like CPU and GPU. A dielectric highly wetting liquid, Novec™ 649 from the 3M Corporation, was used in pool boiling experiments with different surface characteristics: bare copper, a commercial Boiling Enhancement Coating (BEC™) from the 3M Corporation, and the MuSEP coating. A 4 mm-thick heat spreader, with an area of 22 cm 2 , was attached to a heater, with surface dimensions of 2.54 cm by 2.54 cm. The best results were achieved with the MuSEP coating, as it could improve the boiling heat transfer coefficient (HTC) by 108% versus the bare copper surface and by 38% versus the BEC™, at (250±11) W (average heat flux through the boiling surface of (11.3±0.5) W/cm 2 ). At that power, the case temperature was (68±0.1)°C for the MuSEP coating, (79±0.1) °C for the BEC™, and (93±0.1)°C for the bare copper surface. The surface to liquid thermal resistance (R s–l ) was reduced from (0.186±0.008) °C/W to (0.089±0.004) °C/W when boiling on the MuSEP coating compared to the bare copper surface. Also, the MuSEP coating exhibited the lowest thermal resistance at lower power. The reliability of the MuSEP coating was proven after passing more than 22000 integrated hours of tests for functioning CPU in a two-phase thermosyphon cooling prototype and more than 5500 integrated hours in a total immersion cooling application. With a superior boiling performance, low fabrication cost, and reliability, the MuSEP coating could be an essential element for future commercial two-phase cooling solutions.