By sandwiching thermally conductive carbon nanotubes between thin metal foils, nanotape transfers heat away from chips better than solder but with a lightweight flexible material that is cheaper and and more compliant, according to researchers.
Nanoletters - Temperature-Dependent Phonon Conduction and Nanotube Engagement in Metalized Single Wall Carbon Nanotube Films
Interfaces dominate the thermal resistances in aligned carbon nanotube arrays. This work uses nanosecond thermoreflectance thermometry to separate interface and volume resistances for 10 μm thick aligned SWNT films coated with Al, Ti, Pd, Pt, and Ni. We interpret the data by defining the nanotube-metal engagement factor, which governs the interface resistance and is extracted using the measured film heat capacity. The metal−SWNT and SWNT−substrate resistances range between 3.8 and 9.2 mm2 K / W and 33−46 mm2 K / W, respectively. The temperature dependency of the heat capacity data, measured between 125 and 300 K, is in good agreement with theoretical predictions. The temperature dependence demonstrated by the metal−SWNT interface resistance data suggests inelastic phonon transmission.
Besides semiconductors, Stanford is also working with the National Science Foundation (NSF) on a project with the Department of Energy Partnership on Thermoelectric Devices for Vehicle Applications. Here, the nanotape will facilitate the recovery of electrical power from hot exhaust gases using thermoelectric energy converters. According to Goodson, nanotape can more reliably transfer heat to thermoelectric generators, enabling greatly improved fuel economy.
"Today, solder is made very thick to provide mechanical compliance, but our nanotape can replace those solder pads with a thin lightweight material that improves thermal energy management," said professor Ken Goodson, lead researcher for SRC at Stanford University. "Our tape consists of a vertically aligned carbon nanotube forest at its central core, with carefully chosen alloys on both the top and bottom that wet the carbon nanotubes and also will contact to the heat sink and the chip."
To the unaided eye, the nanotape will look like a conventional solder pad, because both the top and bottom are metallic. But inside it will harbor the superior thermal conduction of the carbon nanotubes.
List of publications by the Stanford Microscale heat transfer lab
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