Carbon Nanotube Thermal Interface Materials for Enhanced Thermal Management Project

Thermal interface materials (TIMs) couple heat sources, such as high speed high performance microprocessors, to heat sinks and are critical for efficient thermal management and reliable device operation. A quality TIM has a thermal conductivity (k) approaching 2 W/m-K. Carbon nanotubes (CNTs) are ballistic thermal conductors (k~2500 W/m-K for individual multi-walled CNTs) which have the potential to greatly improve heat transfer and consequently device performance. The near future of spacecraft will likely be more autonomous, require more processing power, and may include the use of multicore processors or next generation FPGAs. These high thermal density devices can create local hotspots which can hinder device performance and reduce reliability. Highly oriented mats of carbon nanotubes (CNTs) with their extremely high thermal conductivity (k ~ 2500 W/m-K for individual multi-walled CNTs) have the potential to improve the performance and reliability of these devices by functioning as a thermal superhighway, maximizing heat transfer away from the source. Successful implementation of CNTs as a thermal interface material (TIM) would be a significant improvement over the status quo as current quality TIMs are in the form of metal or ceramic filled polymers and greases with thermal conductivities ranging from 0.5 to 2 W/m-K. Implementation of CNT TIMs has been limited due to insufficient thermal and mechanical coupling of the CNTs to secondary and tertiary (i.e. non-growth) surfaces. The investigators have proposed a method to improve the thermal and mechanical coupling of CNTs to these surfaces. In this study the investigators will examine theoretical CNT-substrate interfaces for sources of thermal resistance (phonon scattering) and effective coupling for a variety of metallic substrates. Phonon (quantized lattice vibrations) propagation and dispersion at the interface will be investigated using atomistic and quantum mechanical models and the theoretical potential of heat transfer across the examined interfaces evaluated for potential future work. More »