Nanotubes to improve thermal control in electronics

Engineers at the University of Oulu in Finland, and the Rensselaer Polytechnic Institute in New York, US, have shown that carbon nanotube arrays can dissipate heat as effectively as the bulky metallic heatsinks commonly used in electronic devices.

Electronic components can give off considerable amounts of heat when in use. This heat is normally drawn away from circuits by means of heatsinks – finned structures made of conductive metals such as copper or aluminium.

Carbon nanotube microchip cooler. (© Robert Vajtai, Rensselaer Polytechnic Institute)

In place of metal, the Finnish and American researchers use microfin structures made of aligned multiwalled carbon nanotube arrays mounted on the back of silicon chips. The nanotube structures are more flexible and resilient, and 10 times lighter than the commonly-used metal heatsinks.

With increasing miniaturisation of electronic devices, it is a considerable challenge to deal with waste heat. When reduced to sub-millimetre sizes, silicon becomes very brittle, while metal becomes bendable and weak. Carbon nanotube structures, on the other hand, maintain their high strength and excellent conductivity at such small scales.

To make the nanotech heat conductors, thick films consisting of 1.2-mm long nanotubes are grown and detached from silicon/silicon oxide templates, and a laser used to carve out freestanding 10×10 fin blocks. The process employs conventional manufacturing methods, and is scalable.

Cost is not a significant issue, according to Krisztián Kordás, a member of the Oulu team: ‘Any material can be cheap if the quantity necessary for the particular application is sufficiently small. To give an estimate, the materials cost in a large-scale production of nanotube chip coolers is not expected to be more than a few cents or maybe euros.’

Kordás and his colleagues are looking now to increase component size, and improve cooling efficiency and the large scale production process. ‘If we manage to improve the cooler efficiency, and demonstrate efficient cooling for large-size components, nanotube coolers would be very competitive alternatives to any conventional metal coolers.’

Figure: Carbon nanotube microchip cooler. (© Robert Vajtai, Rensselaer Polytechnic Institute).

Further reading: Chip cooling with integrated carbon nanotube microfin architectures, Kordás et al., App. Phys. Lett. 90, 123105 (2007) (subscription required)

Article first published in Nanomaterials News.