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Challenges in the manufacture of glass substrates for electrical and optical interconnect

David A. Hutt (Wolfson School of Mechanical and Manufacturing Engineering, Loughborough University, Loughborough, UK)
Karen Williams (Wolfson School of Mechanical and Manufacturing Engineering, Loughborough University, Loughborough, UK)
Paul P. Conway (Wolfson School of Mechanical and Manufacturing Engineering, Loughborough University, Loughborough, UK)
Fuad M. Khoshnaw (Wolfson School of Mechanical and Manufacturing Engineering, Loughborough University, Loughborough, UK)
Xiaoyun Cui (Wolfson School of Mechanical and Manufacturing Engineering, Loughborough University, Loughborough, UK)
Deepa Bhatt (Wolfson School of Mechanical and Manufacturing Engineering, Loughborough University, Loughborough, UK)

Circuit World

ISSN: 0305-6120

Article publication date: 13 February 2007

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Abstract

Purpose

To present the aims and preliminary findings of a research project to investigate the manufacture of multilayer glass substrates built up from thin glass sheets.

Design/methodology/approach

The approaches that may be taken to create glass substrates and the challenges involved are described. Excimer laser machining was used for the formation of microvias and other features in individual glass sheets. In addition, methods for the electroless copper metallisation of the smooth glass surfaces were studied. Finally, a technique for the lamination of the glass layers using low temperature, pressure assisted bonding was investigated.

Findings

Microvias with 100 μm diameter entry holes were successfully machined in 100 μm thick glass sheets and process windows were identified to reduce debris and hole taper. Using appropriate pre‐treatment steps, electroless copper coatings could be deposited uniformly over the smooth glass surface, however, further improvements in adhesion were found to be necessary. The direct lamination of glass layers was found to be possible using pressure and temperature applied over long periods of time. Improvements to the lamination process were made to reduce the initiation of cracks which were assessed using fatigue testing.

Research limitations/implications

The feasibility of the individual steps in the fabrication of glass substrates has been demonstrated. Further work is necessary to control the processes in order to limit microcrack formation, improve copper coating adhesion and ensure uniform lamination of multiple glass layers.

Originality/value

The use of glass materials could enable the manufacture of substrates for high density electrical interconnect with integrated optical waveguides.

Keywords

Citation

Hutt, D.A., Williams, K., Conway, P.P., Khoshnaw, F.M., Cui, X. and Bhatt, D. (2007), "Challenges in the manufacture of glass substrates for electrical and optical interconnect", Circuit World, Vol. 33 No. 1, pp. 22-30. https://doi.org/10.1108/03056120710723689

Publisher

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Emerald Group Publishing Limited

Copyright © 2007, Emerald Group Publishing Limited

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