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一、引言人们曾设想在晶体管发明之后,由于它具有较低的功率耗散,即使不是全部至少也可以较多地消除对各种冷却问题的担心。然而,当工程师们为了改善电子设备的性能、造价和可靠性,而在一块较小的空间组装大量的电子器件时,发现这种想法是短暂的。事实上,近年来元件级的功率密度已经大大增加。例如,计算机上一块5×5mm~2的芯片,热耗散热量达10W,相应的热流密度达4×10~5,W/mm~2。正如图1所示,这种热流密度仅比太阳表面的热流密度低二个数量级。但是,太阳表面的温度为6000℃,而芯片最高工作温度不过100℃左右。
I. INTRODUCTION It has been assumed that, after the transistor was invented, its low power dissipation would, if not all, at least eliminate much of the concern for various cooling issues. However, engineers found this idea transient when they assembled a large amount of electronics in a small space to improve the performance, cost, and reliability of the electronics. In fact, component-level power density has greatly increased in recent years. For example, a 5 × 5mm ~ 2 chip on a computer can dissipate heat of 10W and a corresponding heat flux density of 4 × 10 ~ 5 W / mm ~ 2. As Figure 1 shows, this heat flux is only two orders of magnitude lower than that of the sun. However, the surface temperature of the sun is 6000 ℃, but the maximum operating temperature of the chip is only about 100 ℃.