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Contact resistance of Ti-Si-C-Ag and Ti-Si-C-Ag-Pd nanocomposite coatings
Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
Department of Materials Chemistry, The Ångström Laboratory, Uppsala University, Sweden.
Department of Materials Chemistry, The Ångström Laboratory, Uppsala University, Sweden.
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2012 (English)In: Journal of Electronic Materials, ISSN 0361-5235, E-ISSN 1543-186X, Vol. 41, no 3, 560-567 p.Article in journal (Refereed) Published
Abstract [en]

Ti-Si-C-Ag-Pd and Ti-Si-C-Ag nanocomposite coatings were deposited by magnetronsputtering on Cu substrates with an electroplated Ni layer. Analytical electronmicroscopy and x-ray diffraction show that the nanocomposites consist of TiC,Ag:Pd, and amorphous SiC. The contact resistance of these coatings against aspherical Au-Co surface was measured for applied contact force up 0 to 5 N. Ti-Si-CAg-Pd coatings with a Ag:Pd strike coating has ~10 times lower contact resistance atcontact forces below 1 N (~10 mΩ at ~0.1N), and ~2 times lower for contact forcesaround 5 N (<1 mΩ at 5 N), compared to the Ti-Si-C-Ag coating.

Place, publisher, year, edition, pages
Springer, 2012. Vol. 41, no 3, 560-567 p.
Keyword [en]
titanium carbide; nanocomposite; physical vapor deposition (PVD); contact resistance; surface roughness; silver palladium
National Category
Natural Sciences
Identifiers
URN: urn:nbn:se:liu:diva-63625DOI: 10.1007/s11664-011-1813-8ISI: 000299930100022OAI: oai:DiVA.org:liu-63625DiVA: diva2:381746
Note
Funding Agencies|European EraSME||Swedish Knowledge Foundation||Swedish Board for Innovation Systems VINN Excellence Center on Functional Nanostructured Materials (FunMat)||Available from: 2010-12-28 Created: 2010-12-28 Last updated: 2017-12-11Bibliographically approved
In thesis
1. Surface Technology for Optical and Electrical Connectors
Open this publication in new window or tab >>Surface Technology for Optical and Electrical Connectors
2010 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

This thesis treats surface engineering with the purpose of improved quality of optical and electricalconnectors with a focus on electroplated and magnetron sputtered materials. In electroforming of tools formanufacturing optical connectors, the influence of ultrasonic agitation on intrinsic stresses and fillingproperties of electroplated Ni has been studied. It is established that the ultrasonic agitation at the substratesurface during deposition impacts the intrinsic stresses making it possible to increase deposition rate viacurrent density, with stress-free or low-stress levels in the Ni layers. Reduced variations of the intrinsicstress over the surface with the current density is a further important result. Filling of grooves byelectroplating of Ni using ultrasonic agitation is demonstrated. This is due to increasing mass transport ofspecies into the grooves compared to conventional pumped agitation. The enhanced filling propertiesmakes it possible to electroplate Ni in the bottom of high-aspect-ratio grooves. In order to industriallyimplement new nanocomposite coatings on electronic connectors, studies have been performed regardingthe thermal diffusion barrier properties against Cu for Ti-Si-C and Ti-Si-C-Ag nanocomposites, depositeddirectly onto Cu substrates or with sputtered Ni, Ti or electroplated Ni as an intermediate coating. Theapplication of an electroplated Ni diffusion barrier coating, hinders Cu from reaching the surface of thenanocomposites. Also, Ti-Si-C-Ag nanocomposite deposited on magnetron sputtered Ni or Ti on Cusubstrates hinder Cu from diffusing to the surface after annealing. The contact resistance of Ag-Pdtopcoated Ti-Si-C-Ag-Pd and Ti-Si-C-Ag nanocomposite coatings in contact with hard gold is shown tocompete with hard gold in contact with itself, as electrical contact coatings at contact forces around 5 N.Ag-Pd topcoated Ti-Si-C-Ag-Pd in contact with hard gold is shown to have approximately the same contactresistance as hard gold in contact with hard gold at contact forces around 0.1 N, which here is in the 10 mΩrange, while Ti-Si-C-Ag nanocomposite coatings in contact with hard gold has a contact resistance that isup to 10 times higher. The overall contribution of this thesis can be summarised as a deeper knowledge andunderstanding of techniques and coatings, that help reduce cost and increase reliability of electronics.

Place, publisher, year, edition, pages
Linköping: Linköping University Electronic Press, 2010. 73 p.
Series
Linköping Studies in Science and Technology. Dissertations, ISSN 0345-7524 ; 1342
National Category
Natural Sciences
Identifiers
urn:nbn:se:liu:diva-63626 (URN)978-91-7393-299-8 (ISBN)
Public defence
2010-11-26, Planck, Fysikhuset, Campus Valla, Linköpings universitet, Linköping, 10:15 (Swedish)
Opponent
Supervisors
Available from: 2010-12-28 Created: 2010-12-28 Last updated: 2016-08-31Bibliographically approved
2. TiC-based nanocomposite coatings as electrical contacts
Open this publication in new window or tab >>TiC-based nanocomposite coatings as electrical contacts
2011 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

This Thesis concerns the advanced surface engineering of novel TiC-based nanocomposite and AgI electrical contact materials. The objective is to make industrially applicable coatings that are electrically conductive and wear-resistant, and have a low coefficient of friction. I have studied electrical contact systems consisting of a Cu substrate with a Ni diffusion barrier and loading support, and a conductive top coating. The contact systems were characterized by x-ray diffraction and photoelectron spectroscopy, analytical electron microscopy, ion beam analysis, nanoindentation, resistivity, and contact resistance measurements. Nc-TiC/a-C/SiC nanocomposite coatings consisting of nanocrystalline (nc) TiC embedded in an amorphous (a) matrix of C/SiC were deposited by magnetron sputtering with rates as high as 16 μm/h. These coatings have a contact resistance comparable with Ag at high loads (~800 N) and a resistivity of 160-770 μΩcm. The electrical properties of the contact can be improved by adding Ag to make nc-Ag/nc-TiC/a-SiC nanocomposites. It is possible to tailor the size and distribution of the Ag grains by varying the fraction of amorphous matrix, so as to achieve good conductivity in all directions in the coatings. Ti-Si-C-Ag coatings have a contact resistance that is one magnitude larger than Ag at lower loads (~1 N), and a resistivity of 77-142 μΩcm. The conductivity of the matrix phase can be increased by substituting Ge, Sn or Cu for Si, which also reduces the Ag grain growth. This yields coatings with a contact resistance twice as high as Ag at loads of 1 N, and a resistivity 274-1013 μΩcm. The application of a conductive top layer of Ag-Pd upon a Ti-Si-C-Ag:Pd coating can further reduce the contact resistance. For barrier materials against Cu interdiffusion, it is shown that conventional electroplating of Ni can be replaced with sputtering of Ni or Ti layers. This is an advantage since both contact and barrier layers can now be deposited in and by the same deposition process. For Ti-B-C coatings deposited by magnetron sputtering, I demonstrate promising electrical properties in a materials system otherwise known for its good mechanical properties. In coatings of low B concentration, the B is incorporated into the TiC phase, probably by enrichment on the TiC{111} planes. The corresponding disturbance of the cubic symmetry results in a rhombohedral TiC:B structure. Finally, it is shown that AgI coatings consisting of weakly agglomerated AgI grains function as solid lubricant on Ag contacts. In an Ag sliding electrical contact, AgI decreases the friction coefficient from ~1.2 to ~0.4. After a few hundred operations, AgI grains have deagglomerated and Ag from the underlying layer is exposed on the surface and the contact resistance decreases to < 100 μΩ.

Place, publisher, year, edition, pages
Linköping: Linköping University Electronic Press, 2011. 63 p.
Series
Linköping Studies in Science and Technology. Dissertations, ISSN 0345-7524 ; 1408
National Category
Natural Sciences
Identifiers
urn:nbn:se:liu:diva-72228 (URN)978-91-7393-030-7 (ISBN)
Public defence
2011-12-02, Planck, Fysikhuset, Campus Valla, Linköpings universitet, Linköping, 10:15 (English)
Opponent
Supervisors
Available from: 2011-11-23 Created: 2011-11-23 Last updated: 2016-08-31Bibliographically approved

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Lauridsen, JonasHögberg, HansEklund, PerHultman, Lars

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