Fujitsu preps carbon nanotube heat-sink

Mobile phone base-station chips to run faster, cooler

Fujitsu has figured out how to cool chips using carbon nanotubes, though it's going to a few years yet before the technology is ready for commercial usage, the company admitted.

The cooling system is a heat-sink, created out of millions of 15µm-long nanotubes. The nanotubes are 'grown' on the wafer substrate using an iron catalyst. The structure of the heat-sink matches the pattern of the electrode 'bumps' on the base of the chip through which it connects to the motherboard.

The chips in question are high-frequency power amplifiers, typically used in mobile phone base-stations. Today, these chips are limited by the heat they generate, which must be quickly dissipated, and by the way they're connected to the motherboard. Currently, the best method to connect them for maximum heat dissipation is not the best way to allow the chips to be driven at ever-higher frequencies. To get the higher frequencies, a different connection method is needed, but it's one that's less able to dissipate the heat.

Fujitsu claims its nanotube heat-sink squares the circle: it's able to dissipate sufficient heat to allow the second, 'flip chip' connection method to be used to operate the chips at higher frequencies.

The company said it will now work to refine the density of the nanotubes around the bumps to improve heat dissipation even further. It said it expects the technology to appear in mobile phone base-stations in around three years' time. ®