NEC designs innovative heat sink in record time

Courtesy of NEC Corporation.

When NEC Computers Inc., Boxborough, MA tapped Coolit to accelerate custom heat sink development for its new dual processors servers, it landed an added and unexpected bonus-a breakthrough in heat sink design.

The seeds were sown as NEC engineers analyzed Coolit models of airflow movement and heat dispersion across elliptical pin fin designs. A conventional elliptical pin fin design maintains a uniform cross-section across its surface. Yet the animated Coolit models were clearly revealing that cooling surface requirements were increasing as air transversed the heat sink. To NEC engineers the fix was obvious: reject conventional topographies and design heat sinks that match the changing thermal demands.

Using Coolit, engineers manipulated base thickness, fin geometry, airflow and the balance among these parameters in the search for the optimum configuration. Four custom heat sink designs were evaluated in only two days. The result was a patent-applied-for design in which pin width and thickness vary to compensate for losses in cooling capacity as air slows down and warms up during its heat sink traverse. In addition, the pins are aligned in rows, unlike conventional designs where they are staggered like bowling pins.

At the leading edge of the heat sink where airflow is maximum, smaller pins deliver the required heat dissipation. The smaller pins also reduce the likelihood of creating an air dam that would reduce downstream cooling. As air moves across the heat sink, its velocity decreases and the pin surface area is increased to compensate.

The unorthodox design shaves 15 deg. C off processor die temperature and cuts the per-piece cost by over 80%. On top of these bonuses, NEC engineers still reaped the original benefits they sought from Coolit: weeks of savings in design, model building and testing time worth thousands of development dollars.


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