Characterization of the mechanical and thermal interface of copper films on carbon substrates modified by boron based interlayers

• Published in: Surface & coatings technology 2011-03, Vol.205 (12), p.3729-3735
• Main Authors: Schäfer, D., Eisenmenger-Sittner, C., Chirtoc, Mihai, Kijamnajsuk, P., Kornfeind, N., Hutter, H., Neubauer, E., Kitzmantel, M.
• Format: Article
• Language: English
• Subjects: Adhesion; Adhesion tests; Adhesive strength; Carbon; Coatings; Copper; Cross-disciplinary physics: materials science; rheology; Deposition; Exact sciences and technology; Infrared; Interlayer; Interlayers; Materials science; Physics; Scanning electron microscopy; Surface treatments; Thermal Contact Resistance
• ISSN: 0257-8972; 1879-3347
• DOI: 10.1016/j.surfcoat.2011.01.039

The manipulation of mechanical and thermal interfaces is essential for the design of modern composites. Amongst these are copper carbon composites which can exhibit excellent heat conductivities if the Cu/C interface is affected by a suitable interlayer to minimize the Thermal Contact Resistance (TCR) and to maximize the adhesion strength between Cu and C. In this paper we report on the effect of boron based interlayers on wetting, mechanical adhesion and on the TCR of Cu coatings deposited on glassy carbon substrates by magnetron sputtering. The interlayers were 5nm thick and consisted of pure B and B with additions of the carbide forming metals Mo, Ti and Cr in the range of 5at.% relative to B. The interlayers were deposited by RF magnetron sputtering from either a pure B target or from a composite target. The interlayer composition was checked by Auger Electron Spectroscopy and found to be homogenous within the whole film. The system C-substrate/interlayer/Cu coating was characterized in as deposited samples and samples heat treated for 30min at 800°C under High Vacuum (HV), which mimics typical hot pressing parameters during composite formation. Material transport during heat treatment was investigated by Secondary Ion Mass Spectroscopy (SIMS). The de-wetting and hole formation in the Cu coating upon heat treatment were studied by Scanning Electron Microscopy (SEM) and Atomic Force Microscopy (AFM). The adhesion of the Cu coating was evaluated by mechanical pull-off testing. The TCR was assessed by infrared photothermal radiometry (PTR). A correlation between the adhesion strength and the value of the TCR which was measured by PTR was determined for as deposited as well as for heat treated samples. ► Investigation of thermomechanical properties of carbon/metal interfaces. ► Application of infrared photothermal radiometry (PTR) for layered media. ► Correlation of mechanical and thermal properties for carbon/metal interfaces.