IBM Researchers Borrow from Mother Nature to Cool Chips
October 30, 2006 Timothy Prickett Morgan
Power and cooling issues are taking center stage in the data center these days, and researchers at IBM working in its Zurich, Switzerland, laboratories are looking to help from Mother Nature to teach them how to better cool the chips that are going into computers.
The fastest processors on the market today are basically hotplates that happen to do computing (yes, that is hyperbole), and while no one is suggesting converting a supercomputer cluster into a grill at the local McDonalds (at least not yet), there are other ways to attack the cooling issue. (Actually, IBM says that chip thermal densities are an order of magnitude higher than a hotplate.) IBM’s chip designers have developed copper, silicon on insulator, and low-k dielectric technologies to make chips denser and more powerful; the company is also a genius at the ceramic packaging that wraps chips. But Zurich researchers at IBM has focused on a unique place in the system–the interface between that ceramic package and the cooling fins that typically are attached to processors.
You may not know it, but you put goo between the chip package and a heat sink, and getting a thin, uniform layer of this goo is critical to get heat to move from the chip to the heat sink. Getting the paste uniform is very difficult, and to do so often requires a lot of pressure, which can crack the chips. To get the heat to transfer better, IBM has created a cap of thermal material that interfaces with the bottom of the heat sink–not on a flat, 2D plane, but through a network of 3D channels that branch out like tree branches or capillary systems. What this does is increase the amount of surface area where the goo comes in contact with the heat sink, which means it can suck off more heat.
Another neat technology that the Zurich lab is working on is called direct jet impingement, and with this method, IBM uses another branching structure to splash water on the chips surface, and within a very short period of time, once heat is transferred to the water, the system reverses and sucks the water back off the chip again. This system has over 50,000 tiny nano-nozzles to squirt water on the chip and suck it back off again. This system is completely sealed, and cannot leak out onto the computer components. IBM says that this variant of water cooling also has a tree-like structure in terms of the pattern by which the water is delivered to the surface of the chip, and that it can pull up to 370 watts per square centimeter off of a chip. Current air-cooled methods used with PCs and servers can pull off about 75 watts per square centimeter.
If IBM can create a chip cooling method that can pull offer six times more heat than it can do today, that means it can ramp up clock speeds or make bigger, hotter chips. Which is why Big Blue is motivated to do such research.