Optimization of carbon nanotube thermal interfaces
Abstract
This study aims to develop methods to enhance CNT thermal interface performance by engineering the array in terms of volume fraction as well as develop innovative bonding techniques at a CNT/substrate contact. In particular, unbonded, semi-bonded, and fully bonded CNT TIMs are fabricated and thermally characterized using transient PA and a steady state 1D reference bar techniques. The main objective of this work is to mitigate the phonon `bottleneck' at solid-solid contacts by means of increasing the area of contact and moving towards more covalently bonded interfaces. Because of their extraordinarily high thermal conductivities and mechanical conformability, carbon nanotubes (CNTs) offer a compelling alternative to traditional thermal interface materials in electronics packages. The conformability feature is particularly advantageous in addressing CTE mismatch under extreme thermal conditions encountered in advanced electronics applications. Prior results for dry CNT array thermal interface materials compare very favorably with state-of-the-art thermal greases and other non-bonded materials. The thermal interface behavior of CNT-coated Cu foils and the commensurate effects of a wide range of synthesis parameters are reported in this thesis. The results indicate that low thermal interface resistance values are possible for solder-enhanced interposers with and without the inclusion of paraffin wax, reaching levels below 10 mm 2 K/W as measured by the one-dimensionalreference bar technique. General observations from parametric variations such as CNT array height and volume fraction on interface resistance measured by the reference bar technique are complemented by a photoacoustic method for unbonded, partially-bonded and fully-bonded interfaces. Lastly, an innovative bonding technique that utilizes a metal-orgranic precursor to create a palladium (Pd) bond at the MWCNT/Ag interface is shown to be a promising avenue with thermal resistances measuring near 5 mm 2 K/W by PA and 25 mm 2 K/W by referencebar.
Degree
M.S.M.E.
Advisors
Fsiher, Purdue University.
Subject Area
Mechanical engineering
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