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Electrochemically based low-cost high precision processing in MOEMS packaging
Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
SP Technical Research Institute of Sweden, Sweden/Jönköping University, Sweden.
Acreo AB, Norrköping/Kista, Sweden.
Acreo AB, Norrköping/Kista, Sweden.
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2009 (English)In: Electrochimica Acta, ISSN 0013-4686, E-ISSN 0019-4686, Vol. 54, no 9, 2458-2465 p.Article in journal (Refereed) Published
Abstract [en]

Precision processing in MOEMS (micro-opto-electromechanical systems) packaging has been studied based on electrochemical processes with the purpose of establishing technology for low-cost multifunctional encapsulation of microsystems and assembly of opto-electric access links in polymer.

The electrochemically based processes studied in this paper include:

1. Electroforming of a polymer moulding tool (stamper) in a nickel sulphamate electrolyte on a highprecision 3D etched silicon template.

2. Patterning of 3D surfaces by an electrophoretic photoresist.

3. Precision plating of Au and Sn for self-alignment of chips by eutectic Au-Sn solder.

The results show that nickel stampers with adequately low internal stress can be electroformed on 3D silicon wafers. Furthermore, 3D polymer samples manufactured by the nickel stampers can be patterned with metal lines down to 20 mu m width using electrophoretic photoresist. Finally, eutectic Au-Sn solder bumps are realized by electroplating of Au and Sn followed by reflowing, satisfying the demands on dimension and alloy composition control over a 4 in. Si wafer.

Place, publisher, year, edition, pages
2009. Vol. 54, no 9, 2458-2465 p.
Keyword [en]
Electroforming, Micro-replication, 3D patterning, Self-aligning soldering, MOEMS packaging
National Category
Natural Sciences
URN: urn:nbn:se:liu:diva-17751DOI: 10.1016/j.electacta.2008.03.084OAI: diva2:211825
Available from: 2009-04-18 Created: 2009-04-17 Last updated: 2016-08-31Bibliographically 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.
Linköping Studies in Science and Technology. Dissertations, ISSN 0345-7524 ; 1342
National Category
Natural Sciences
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)
Available from: 2010-12-28 Created: 2010-12-28 Last updated: 2016-08-31Bibliographically approved

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