Advanced Thermal Architecture for Cooling of High Power Electronics

Introduction
The increase in computing power is the result of packing more transistors into a chip and by cycling them faster, contributing to exponentially increasing power densities. There has also been a huge increase in the heat dissipation per unit volume. Not only are more transistors being packed into a chip and more chips into a microprocessor, but more microprocessors (and memory chips) are being packaged in a computer system, more computer systems are being mounted in a rack or cabinet, and many more cabinets are being mounted in a room.

Figure 1 summarizes the challenges facing the industry. The red line shows the trend of decreasing case temperature as demanded by the increasing clock speed. The blue line shows the trend of rising enclosure temperature as caused by the increasing heat dissipation in the enclosure. The difference between the two indicates the “thermal budget” available for the design of cooling devices/systems. As the two lines converge, the thermal budget shrinks, presenting increasing challenges to the thermal design. As the thermal budget approaches zero, refrigeration systems will have to be used to provide the necessary
cooling. However, reliability issues, additional power needs, increased operating cost and adverse environmental impacts are among the negatives associated with refrigeration systems. Therefore, one challenge facing the industry is how to avoid or delay the use of refrigeration systems for electronics cooling. This article presents a new approach to this challenging problem. We propose a thermal architecture concept for analyzing the different levels of thermal problems existing in typical electronic  enclosures. An advanced thermal architecture that utilizes highly effective and passive components is discussed. Finally, the benefits and challenges in implementing such architecture are examined.

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