Traditional thermal interface materials include greases, waxes and a foil made from a metal called indium. The most common type of thermal interface material most computer enthusiasts are used to is a paste with a white or silver color. Most heat sinks for computer use also include a pink colored pad on them to conduct heat from the CPU to the heat sink.
A group at Purdue University has demonstrated a way to make a more efficient thermal interface material using carbon nanotubes. The researchers on the project include Placidus B. Amama, a postdoctoral research associate at the Birck Nanotechnology Center in Purdue's Discovery Park, doctoral student Baratunde A. Cola, Timothy D. Sands, director of the Birck Nanotechnology Center and the Basil S. Turner Professor of Materials Engineering and Electrical and Computer Engineering; and Xianfan Xu and Timothy S. Fisher, both professors of mechanical engineering.
The researchers have demonstrated a method of growing what’s described as a forest of tiny carbon nanotube cylinders on the surface of a computer chip to enhance the flow of heat to a critical point where the chip connects to a cooling device according to Purdue University News. The nanotube thermal interface material being grown directly on the surface of the chip allows the material to completely fill gaps and gouges on the surface of the chip.
Cola claims, “The method developed by the Purdue researchers enables them to create a nanotube interface that conforms to a heat sink's uneven surface, conducting heat with less resistance than comparable interface materials currently in use by industry." Cola also said, "The tubes bend like toothbrush bristles, and they stick into the gaps and make a lot of real contact.”
The carbon nanotubes are grown directly on the surface of the chip using templates created from branching molecules called dendrimers. The dendrimers are then seeded with catalyst particle-laden silicon inside a chamber and exposed to methane gas. The application of microwaves breaks down the methane that contains carbon. The catalyst particles prompt the nanotubes to assemble and grow vertically on the chip.
Carbon nanotubes have already proven their use in computing thermaldynamics. OCZ Technology announced earlier this year its intention to use a CNT-based materials in high-end consumer heatsinks.
There is no word on when or if this process might see commercial applications. However, the better the thermal interface material is at transferring heat from the chip to the heat sink, the smaller the heat sink can be. This will lead to smaller cooling systems, smaller computers, and less power required to cool the chip.
Computer manufacturers should be keen on exploring this technology further. Carbon nanotubes are being looked at for a variety of applications from nanotube batteries to using nanotubes to send impulses to nerves inside the body.