IBM Borrows From Biology To Get Cooling Spray On Chips

Taking a page from biology texts, IBM researchers believe they're close to perfecting technology that will become the latest entrant in the nascent field of cooling microprocessors by spraying them with liquid.

Power densities of some processors have reached around 100 watts per square centimeter and are expected to increase to 300 watts per square centimeter or more as transistor widths shrink and the number of processing elements on chips increases. Chipmakers are looking at ways of attacking the problem as close to the source of the heat as possible--meaning the chip itself.

At its research lab in Zurich, Switzerland, IBM has been working on technology that may eventually incorporate an array of up to 50,000 tiny nozzles that cool chips by squirting them with liquid.

"The cooling of the data center is an increasingly important problem, and the solution starts at the chip level," says Bruno Michel, manager of the advanced thermal packaging research group at IBM's Zurich lab.

Processors typically are cooled by flat plates affixed to chips using a thin paste. IBM researchers have developed a plate with a network of branched channels on its surface. The pattern allows the paste to be spread more evenly than in the past, meaning it can draw off more heat.

Systems of so-called hierarchical patterns can be found throughout nature, including among tree roots and in leaves, as well as in the human circulatory system. Such channels can serve large areas without expending a great deal of energy.

IBM is close to taking the technology into commercial application, Michel says, where "it can spread across the entire industry and become a new standard within two years."

In looking several years out, Michel believes the cooling capability will be extended with the use of direct jet impingement, an approach that sprays water onto the back of the chip and then sucks it off within a closed system around the chip.

The team in Zurich has demonstrated the ability to cool chips with power dissipation of 370 watts per square centimeter when using water as a coolant, or about six times greater than the current limits of air-cooling techniques.

The idea of taking heat off processors with liquid sprays isn't as radical as it sounds. Several companies are either selling or experimenting with technologies that use direct-attached spraying to cool chips, including Hewlett-Packard, Liebert, and SprayCool.