Polymer Nanofibers Could Beat the Heat in Chips

Image: Virendra Singh

Back in 2001, Patrick P. Gelsinger, at the time the chief technology officer at Intel Corp., suggested that if the trend towards hotter and hotter chips continued—which thankfully it did not—microprocessors would generate heat equivalent to the temperature found on the surface of the sun within a decade (the time that we currently inhabit).

In order to overcome this thermal management issue, researchers have, for the past decade, been researching and using different nanomaterials and nanostructures to beat the heat.

Now researchers at the Georgia Institute of Technology have developed a polymer with aligned arrays of nanofibers that acts as a thermal interface for electronics. This alignment, they report, makes it 20 times better at conducting heat than the original polymer.

The research, which was published in the journal Nature Nanotechnology (“High thermal conductivity of chain-oriented amorphous polythiophene”), produced the new polymer from a conjugated polymer, polythiophene, in which aligned polymer chains in nanofibers facilitate the transfer of phonons—but without the brittleness associated with crystalline structures. Phonons are vibrations in a crystal lattice that carry heat.

The researchers believe that the resulting polymer could be used to draw heat away from electronic devices in servers, automobiles, high-brightness LEDs and some mobile devices.

“Thermal management schemes can get more complicated as devices get smaller,” said Baratunde Cola, an assistant professor at the Georgia Institute of Technology, in a press release. “A material like this, which could also offer higher reliability, could be attractive for addressing thermal management issues. This material could ultimately allow us to design electronic systems in different ways.”

While most thermal management systems for computers have relied on fans as a solution, the real hurdle has been getting heat from the chip to the heat sink. This particular issue has been addressed by solder, which is liable to fail after a few thousand cycles of heat-induced expansion and contraction.  This new polymer, which adheres well to devices, would be fabricated on heat sinks and heat spreaders, replacing the solder.

“Polymers aren’t typically thought of for these applications because they normally degrade at such a low temperature,” Cola said in the release. “But these conjugated polymers are already used in solar cells and electronic devices, and can also work as thermal materials. We are taking advantage of the fact that they have a higher thermal stability because the bonding is stronger than in typical polymers.”

The polymer is produced in an electrochemical polymerization process in which an alumina template with tiny pores is covered with an electrolyte containing monomer precursors. An electrical potential is applied to the template that causes electrodes at the base of each to attract the monomers in the electrolyte, forming the hollow nanofibers. The nanofibers are cross-linked through electropolymerization and the template is then removed. The resulting material is applied to the electronic devices using water or some other solvent that spreads the fibers through capillary action and van der Waal forces, the repulsive or attractive forces between molecules.

While the researchers don’t fully understand this fabrication technique theoretically, they are confident that it could be scaled up for commercialization. “There are some challenges with our solution, but the process is inherently scalable in a fashion similar to electroplating,” said Cola in the release. “This material is well known for its other applications, but ours is a different use.”

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Nanoclast

IEEE Spectrum’s nanotechnology blog, featuring news and analysis about the development, applications, and future of science and technology at the nanoscale.

 
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