IMMERSION COOLING OF MICROELECTRONIC CHIP WITH MICROCONFIGURED SURFACE

虽然近年来CMOS技术的发展使得芯片级散热率有了相当大的下降，但很明显，随着电子器件封装密度和开关速度的提高，散热率将再次上升到一个较高的水平。利用介电液体直接浸没冷却电子器件是一种很有前途的方法，因为它具有很高的冷却潜力。然而，这并不是在实际使用中，主要是由于与使用具有高润湿性的介电液体相关的沸腾起始所需的高壁过热。在本研究中，实验研究了新开发的具有微回入腔的处理表面的FC-72沸腾传热。利用微电子加工技术在硅片上制备了表面结构。采用三种孔径（1.6 μ m、3 μ m和9 μ m）和两种孔径（2 μ m）的组合处理了几种表面，并在表面光滑的情况下测试了微再入腔的密度（8 μ m 1/cm^2和96 μ m 10^ 31 /cm^2）。实验在3 K和25 K的液体过冷下，用脱气和溶解的FC-72进行。结果表明：(1)沸腾初始壁面过热度与溶解气体含量密切相关，而受腔口直径和液体过冷度的影响较小。(2)对于脱气的FC-72，沸点起始过热普遍高于非均相成核理论的预测，该理论假定胚泡在腔口处的力平衡。这表明，即使是孔径较小的重入腔，如1.6 mum，对高润湿性的液体也不起作用。(3)微可入腔硅片的传热性能较光滑硅片有明显改善。(4)气溶FC-72的换热性能高于脱气FC-72。少

Although the recent developments of CMOS technology has resulted in a considerable decrease in the chip-level heat dissipation rate, it is obvious that the heat dissipation rate will increase again to a high level as the packaging density and switching speed of the electronic devices increase. Direct immersion cooling of electronic devices by use of dielectric liquids has been a promising method because of its high cooling potential. However, this is not in practical use mainly due to a high wall superheat required for boiling incipience associated with the use of dielectric liquids with a high wettability.In the present reasearch, boiling heat transfer of FC-72 from newly developed treated surfaces with micro-reentrant cavities was studied experimentally. The surface structure was fabricated on a silicon chip by use of microelectronic fabrication techniques. Several kinds of treated surfaces with the combinations of three cavity mouth diameters (1.6 IOTAm, 3 mum and 9 mum) and two num … More ber densities of the micro-reentrant cavities (8I 1/cm^2 and 96CHI 10^3 1/cm^2) were tested along with a smooth surface. Experiments were conducted at the liquid subcoolings of 3 K and 25 K with degassed and gas-dissolved FC-72. The results were as follows :(1)While the wall superheat at boiling incipience was strongly dependent on the dissolved gas content, it was little affected by the cavity mouth diameter and the liquid subcooling.(2)For the degassed FC-72, the boiling incipience superheat was generally higher than the prediction of the heterogeneous nucleation theory which assumed the force balance of an embryonic bubble at the cavity mouth. This suggest that even the reentrant cavity with small mouth such as 1.6 mum is inactive for the liquid with high wettability.(3)The heat transfer performance of the silicon chip with micro-reentrant cavities was considerably improved over the smooth chip.(4)The heat transfer performance of the gas-dissolved FC-72 was higher than that of the degassed FC-72. Less