IBM to cool layered chips with water

A 3D processor structure that integrates hair-thin water pipes will provide a solution for heat management in high-processing computers, scientists at Big Blue's Zurich Research Lab say.

Scientists from the IBM Zurich Research Lab and the Fraunhofer Institute in Berlin are working on a microchip that uses micropipes of water to cool itself, IBM announced Thursday.

The chip's components are built in a 3D stack instead of side by side on a silicon wafer.

This diagram illustrates the chip-cooling concept. Water in a cooling container (purple) is pumped through integrated spaces between the chip's layers (orange). IBM

Chips built in a three-dimensional stack formation offer more pathways for info to be processed and can shorten the distance chip information needs to travel by as much as 1,000 times, according to Thomas Brunschwiler, a senior engineer in the Advanced Thermal Packaging Group at the IBM Zurich Research Lab who has been working on the chip for almost two years.

The trouble is that this type of experimental chip structure also generates a large amount of heat.

To address that problem, the team has developed a cooling system consisting of micropipes of water as thin as a human hair (50 microns) that are interspersed between each chip layer.

To prevent an electrical short, the hairlike water pipes are hermetically sealed from the chip's other components first with a silicon wall and then with a layer of silicon oxide, according to Brunschwiler.

To bond the individual pipes from layer to layer without damaging other chip components, the scientists used a solder consisting of a mixture of gold and tin, which has a low melting point.

"This process enabled us to completely seal off the joints. Then we can use water, which is superior to other coolants," Brunschwiler said.

The water-cooled chip, which is intended for use in supercomputers, is 5 to 10 years away from being commercially available. "But before that, one would probably see chips with one core layer and a memory layer sitting on top that can still be cooled with (an) outside system," Brunschwiler said.

While unique in its microscopic scale, IBM's use of water to cool down the heat generated by computer processing is not novel.

Companies like IBM and Hewlett-Packard sell server racks with liquid cooling systems. Researchers at Ireland's Tyndall Institute and University of Limerick announced in March that they are working on a liquid cooling system incorporated into the packaging that encases chips. And in April, IBM announced a supercomputer that uses water alongside its processors to cool them.

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