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Plastic deformation processes in Cu/Sn bimetallic films

Published online by Cambridge University Press:  31 January 2011

K.S. Kumar*
Affiliation:
Division of Engineering, Brown University, Providence, Rhode Island 02912
L. Reinbold
Affiliation:
Division of Engineering, Brown University, Providence, Rhode Island 02912
A.F. Bower
Affiliation:
Division of Engineering, Brown University, Providence, Rhode Island 02912
E. Chason
Affiliation:
Division of Engineering, Brown University, Providence, Rhode Island 02912
*
a)Address all correspondence to this author. e-mail: Sharvan_Kumar@brown.edu This author was an editor of this journal during the review and decision stage. For the JMR policy on review and publication of manuscripts authored by editors, please refer to http://www.mrs.org/jmr_policy
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Abstract

Although the driving force for the growth of Sn whiskers from the surface of Sn coatings on copper is thought to be internally generated stress due to the formation of Cu6Sn5 at the Cu/Sn interface, little is known about the nature of this internal stress and how it cracks the surface Sn oxide (an important precursor to whisker formation). Arguments based on elasticity alone do not appear to be sufficient and suggest an important role for plastic deformation. Direct observations, made by transmission electron microscopy of cross-sectioned bimetallic Cu/Sn thin-film specimens, confirm plastic deformation of the Sn grains due to the formation of Cu6Sn5. Dislocation motion and pile-up at the surface Sn oxide, rotation associated with subgrain boundary formation, interaction of the subgrain boundaries with the Sn surface, and diffusional processes are various mechanisms that can produce stress at the Sn surface and crack the Sn oxide.

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Articles
Copyright
Copyright © Materials Research Society 2008

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References

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