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MUNICH, Germany Researchers from IBM's Zurich labs have made significant progress in technologies to cool semiconductor chips. The scientists were inspired by the ways nature disperses liquids in tree leaves or even the human body.
With power densities of up to 100 watts per square centimeter, today's computer chips develop up to ten times more heat compared to a standard hotplate. Thus, cooling the silicon circuits becomes increasingly important. And, according to the IBM researchers, future chips may attain even higher power densities which could create surface temperatures of up to 6000 degrees Celsius if not cooled.
At the BroadGroup Power and Cooling Summit in London, IBM now presented an approach for improving the chip cooling. The so called "high thermal conductivity interface technology" allows a twofold improvement in heat removal over current methods. In a first implementation step which according to Big Blue is very close to be used in serial production, the technology aims at better thermal contact between the chip package and components used to draw the heat away including heat sinks.
The researchers developed a chip cap with a network of tree-like branched channels on its surface. The pattern is designed such that when pressure is applied, the paste used to improve thermal contact between chip package and heat sink spreads more evenly and the pressure remains uniform across the chip, compared to today's solutions. This allows the right uniformity to be obtained at half the pressure, and a ten times better heat transport through the interface, IBM says.
This design used by the IBM researchers is borrowed from biology. Systems of hierarchical channels can be found manifold in nature, like tree leaves, roots, or the human circulatory system. Theses systems can serve large volumes with little energy, the researchers found.
However, the researchers also came to the conclusion that current cooling technologies, typically using air as the medium to transport the heat off the chip, have essentially reached their limits with the current generation of electronic products. And the energy needed to cool computer systems is approaching the power used for calculations, thus almost doubling the overall power budget
"Cooling is a holistic challenge from the individual transistor to the datacenter. Powerful techniques, brought as close as possible to the chip right where the cooling is needed, will be crucial for tackling the power and cooling issues, " said Bruno Michel, manager of the Advanced Thermal Packaging research group at IBM's Zurich lab.
That's where IBM's second implementation step becomes relevant. The Zurich researchers took their concept of branched channel design even further and now are developing what they call a promising approach for water-cooling. Called direct jet impingement, it squirts water onto the back of the chip and sucks it off again in a closed system using an array of up to 50,000 micronozzles and a complicated tree-like branched return architecture.
The team has demonstrated cooling power densities of up to 370 Watts per square centimeter with water as coolant, more than six times beyond the current limits of air-cooling techniques at about 75 Watts per square centimeter. Yet, the system uses much less energy for pumping than other cooling systems do, the researcher said. However, this system is several years away from industrial use.
IBM is in close contact with several chip vendors for licensing the technology, a company spokesperson said. The first implementation step, using heat conducting paste, could be available for the next chip generation in about one year.