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Tiny Pump Cools Chips

Computer fans could get some relief from charged particles that create a cooling breeze.

Researchers have built a tiny silicon-based device that can effectively chill a surface, providing a novel, more effective way to cool microchips. The new device, designed and fabricated by engineers at Intel, the University of Washington in Seattle, and Belmont, MA-based Kronos Advanced Technologies, uses ionized air and an electric field to cool the surface.

Infrared images show how a new micro-cooling device uses ions and an electric field to cool a heated surface. Top: the ion pump is off. Bottom: the pump is on. (Credit: University of Washington)

Computers are heating up with each new generation of chips, as more and more heat-producing transistors are crammed onto them. Indeed, experts say that by the end of this decade, the classic cooling solution–using metal heat sinks to draw heat away from chips, and a rotary fan to cool the heat sinks and push the hot air out of computers–will no longer be good enough.

Fan technology, in particular, is hard to improve. “There’s not much more that can be done to optimize [fans],” says Alex Mamishev, a professor of electrical engineering at the University of Washington, who led the development of the new technology. The chip-cooling ion pump that Mamishev and colleagues are proposing is much smaller than heat sinks and fans, and, since it’s made of silicon, could eventually be integrated into the chip-making process, making it potentially more economical. In addition, if added to a heat sink, the ion pump could cool chips to lower temperatures than are currently possible with standard fans.

The researchers cooled a spot on a surface, comprising a couple of square millimeters in area, by 25 degrees Celsius. The voltage being passed through the electrode tip, which sits a couple of millimeters above the collector electrode, can be modified to cool the chip to different temperatures, or to adjust the area that’s cooled, says Mamishev.

The pump has two basic parts. An electrode tip emits a high voltage that strips electrons from molecules of oxygen and nitrogen in the air, ionizing them. These positively charged ions then flow from the tip to a negatively charged collector electrode. As the ions stream to the collector electrode, “they drag the surrounding air with them, creating a net flow of air,” explains Stephen Montgomery, a senior systems engineer at Intel who worked on the project.

Intel, which is a leading researcher in advanced chip technology, is looking at a number of methods for cooling future chips. But Montgomery says the device developed at the University of Washington “is one of the more promising technologies.” That cooling, Montgomery says, can be done with fairly high efficiency and low power, and it’s scalable, meaning it could be easily mass produced, making it easier to integrate into a large number of chips.

A different advanced method of cooling chips involves using pipes to pump liquid coolant throughout the system, similar to the way a car’s engine is cooled. Apple’s new Mac Pro desktop computer, for instance, uses a pump that pushes water through pipes. But these water-cooling systems are complex and expensive, Mamishev says.

The ion pump is a “potentially important enhancement,” says Thomas Kenny, professor of mechanical engineering at Stanford University. But he adds that it’s still unknown whether the system will face economic and technical challenges similar to those with water-cooled systems.

Mamishev’s team is not alone in the use of ion pumps to cool chips. Similar technology developed at Purdue University in West Lafayette, IN, is being commercialized by a startup called Thorrn Micro Technologies. Their approach is to use metal wires instead of a silicon tip, says Suresh Garimella, professor of mechanical engineering at Purdue. Applying a strong voltage along the wire creates an electric field that ionizes air along its length, not just at the tip, he explains. The company is developing a system for cooling laptops and other portable devices.

Mamishev says there will be challenges with his group’s technology as they try to integrate an ion pump into an actual product. Because of the high voltages used to generate the cooling effect, there could be an accumulation of static charge, hindering device performance, or the voltage could break down insulation in parts of the circuit. “You have to be careful,” he says. Also, the group needs to do tests to determine the longevity and reliability of the ion pump.

The researchers are currently developing a prototype ion pump, which is built into a heat sink. Mamishev expects the technology to be ready for commercialization in servers, desktop computers, and laptops within two years.


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