Solder-bonded carbon nanotube thermal interface materials

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.