IBM cools chips with thin paste

Ben Ames, IDG News Service

As TechWorld reported last May, IBM researchers have found a way to draw twice as much heat off hard-working computer chips, clearing the way for server farms and data centres to use denser, faster processors.

The researchers discovered a better way to squeeze thermally conductive paste between hot chips and their heat sinks, the company announced at last week's BroadGroup Power and Cooling Summit in London.

IBM’s water cooling module (in black) is much smaller than an equivalent copper heat sink

Inspired by the natural branching patterns of tree roots and human veins, the IBM researchers discovered they could move a large volume of paste with very little energy, avoiding the danger of damaging or cracking chips as they expand at high temperatures.

This advance will allow engineers to design more powerful chips and continue to follow the Moore’s Law trend of shrinking transistors to ever-smaller sizes, said Bruno Michel, manager of the advanced thermal packaging research group at IBM’s Zurich Research Laboratory.

As chips become denser, they are increasingly constrained by their own heat, with modern processors using up to 100 watts per square centimetre. That is already pushing the upper limit of current cooling technology, which relies on fans to blow air over heat sinks. Some large server farms need so many fans that IT managers spend as much money to cool the chips as they do to run them.

Because of that budget paradox, many computer vendors have found that cooling systems have changed from mere technical detail into great marketing pitch.

When it launched a range of blade and rack servers in August, IBM gave equal billing to its fast chips and its new cooling technique. The "Cool Blue" feature sucks heat out of racked servers by running liquid through the enclosure doors.

Likewise, Dell founder Michael Dell boasted at a trade show on Monday that his company’s latest desktops and servers would use less electricity—and produce less heat—thanks to more efficient processors. Chip manufacturers claiming to make those more efficient, cooler processors include Advanced Micro Devices with its "Rev F" Opteron, Intel with its "Woodcrest" Xeon 5100 and future "Clovertown" quad-core Xeon, and Sun Microsystems with its UltraSparc T1.

But future chips will get even hotter, so the IBM researchers have already begun testing an even better approach, cooling chips by spraying them with water instead of air. This "direct jet impingement" method uses an array of 50,000 tiny nozzles circulating water in a closed loop, protecting the delicate chips’ circuits from getting wet. In early results, the system has absorbed the power of 370 watts per square centimetre, about four to six times better than current air-cooling methods.

For more detail on this technology, take a look at the feature we published following our visit to IBM's Zurich research labs earlier in the year.