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  • Heat Sink Offers Better Cooling

Photonics Spectra
Jan 2000
Dr. James P. Smith

COLUMBUS, Ohio — Microchannel heat sinks are commonly used to cool solid-state radar systems, diode lasers, and mainframe and supercomputers. They can remove heat 50 times more efficiently than conventional methods using liquid cooled cold plates. Recently, a two-layer microchannel heat sink design was developed that promises to increase the cooling efficiency of existing single-layer designs and to remedy several of their limitations. Kambiz Vafai and Lu Zhu, researchers at Ohio State University, reported on the new design in a recent issue of the International Journal of Heat and Mass Transfer.

One drawback of single-layer microchannel heat sinks is the relatively higher temperature rise along the microchannels compared with traditional heat sinks. Temperatures can vary significantly across the chip, producing thermal stress in chips and packages. Increasing the pressure drop across the channels can control the temperature rise along the channels, but a larger pressure drop forces coolant to move faster through the channels. This requires greater pumping power and bulkier packaging, and it generates more noise. The two-layer system sends coolant in countercurrent directions and eliminates the temperature gradient.

This dual-microchannel heat sink doubles the number of channels in a single-layer design, allowing coolant to penetrate more effectively in the system. The tubes measure 1/16 in. in diameter.

Vafai said that the two-layer microchannels can be manufactured using the same equipment and processes as those employed by the electronics semiconductor industry. The highly sophisticated, commercially available equipment and expertise of the semiconductor industry should make the manufacture of dual-layer devices easily achievable. He added that the cost of the system should be similar to that of conventional microchannel cooling systems.

The researcher said that the use of dual microchannels for laser cooling is simpler than for microelectronics cooling. The technique can be used in a variety of cooling processes as long as the surface area is within certain limits. He has demonstrated that the method works quite well for surfaces with diameters of 10 cm.

The next hurdle in the product's commercialization is completion of the patent process. Vafai said several computer and electronics manufacturers have expressed interest in licensing the technique.

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