Solder-Bonded Carbon Nanotube Thermal Interface Materials

Barako, M.T., Gao, Y., Marconnet, A.M., Asheghi, M., Goodson, K.E. "Solder-Bonded Carbon Nanotube Thermal Interface Materials." IEEE Intersociety Conference on Thermal and Thermomechanical Phenomena in Electronic Systems (ITHERM) 2012, May 30 - June 1, San Diego, CA.

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Vertically-aligned carbon nanotube (CNT) films offer an attractive combination of properties for thermal interface applications, specifically high thermal conductance and mechanical
compliance. In this work, we examine the use of a solder bonding layer to
attach and transfer CNT films from the silicon growth substrate onto metalized
surfaces. Indium foil is considered as a bonding layer for low-temperature
(<150°C) applications while a tin-plated aluminum/nickel foil is used for
high temperature applications (<1000°C). The intrinsic thermal conductivity
of the CNT film and the thermal boundary resistances between the CNT film and the
surrounding materials are measured with comparative infrared microscopy before
and after solder bonding. The thermal properties are measured over a range of
applied compressive stress. In general, compressive stress reduces the thermal
boundary resistance and improves the thermal conductivity of the CNT films. Solder
bonding of the exposed (non-growth) interface reduces the thermal boundary
resistance by up to a factor of 30 over a dry unbonded contact. 

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