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Evolution of microstructure and stress of and associated whisker growth on Sn layers sputter-deposited on Cu substrates

Published online by Cambridge University Press:  31 January 2011

M. Sobiech
Affiliation:
Max Planck Institute for Metals Research, D-70569 Stuttgart, Germany; and Robert Bosch GmbH, D-72770 Reutlingen, Germany
C. Krüger
Affiliation:
Institute for Materials Science, University of Stuttgart, D-70569 Stuttgart, Germany
U. Welzel*
Affiliation:
Max Planck Institute for Metals Research, D-70569 Stuttgart, Germany
J.Y. Wang
Affiliation:
Max Planck Institute for Metals Research, D-70569 Stuttgart, Germany
E.J. Mittemeijer
Affiliation:
Max Planck Institute for Metals Research, D-70569 Stuttgart, Germany; and Institute for Materials Science, University of Stuttgart, D-70569 Stuttgart, Germany
W. Hügel
Affiliation:
Robert Bosch GmbH, D-72770 Reutlingen, Germany
*
a)Address all correspondence to this author. e-mail: [email protected]
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Abstract

After sputter deposition of Sn (layer thickness of 350 nm) on Cu substrates and during subsequent aging at room temperature, Cu and Sn reacted to form the intermetallic phase Cu6Sn5 in the Sn layer at the Cu/Sn interface, which led within a few hours of aging to the development of a compressive stress parallel to the Cu/Sn interface in the Sn layer. One day after aging at room-temperature whisker formation occurred on the surface of the Sn layer. It was shown that whisker growth is associated with long-range Sn diffusion parallel to the Cu/Sn interface. Sn layers of the same thickness sputter deposited on pure Si substrates exhibited throughout the same aging time at room temperature a tensile stress parallel to the Cu/Sn interface (no intermetallic phase formation took place) and whisker formation did not occur. The interrelationship of intermetallic compound formation, stress development, and whisker growth is discussed.

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Articles
Copyright
Copyright © Materials Research Society 2010

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References

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