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Phase formation at the Sn/Cu interface during room temperature aging: Microstructural evolution, whiskering, and interface thermodynamics

Published online by Cambridge University Press:  27 June 2011

Matthias Sobiech ,
Carmen Krüger ,
Udo Welzel ,
Jiang-Yang Wang ,
Eric Jan Mittemeijer  and
Werner Hügel
Matthias Sobiech
Affiliation:
Max Planck Institute for Metals Research, D-70569 Stuttgart, Germany; and Robert Bosch GmbH, D-72770 Reutlingen, Germany
Carmen Krüger
Affiliation:
Institute for Materials Science, University of Stuttgart, D-70569 Stuttgart, Germany
Udo Welzel*
Affiliation:
Max Planck Institute for Metals Research, D-70569 Stuttgart, Germany
Jiang-Yang Wang
Affiliation:
Max Planck Institute for Metals Research, D-70569 Stuttgart, Germany
Eric Jan Mittemeijer
Affiliation:
Max Planck Institute for Metals Research, D-70569 Stuttgart, Germany; and Institute for Materials Science, University of Stuttgart, D-70569 Stuttgart, Germany
Werner Hügel
Affiliation:
Robert Bosch GmbH, D-72770 Reutlingen, Germany
*
a)Address all correspondence to this author. e-mail: u.welzel@mf.mpg.de
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Abstract

The time-resolved evolution of intermetallic phase formation in the system pure Sn (polycrystalline coating with a thickness of several microns) on pure Cu (polycrystalline bulk substrate) was investigated in detail by means of focused ion beam and transmission electron microscopy and x-ray diffraction during aging at room temperature for a period of about 1 year. The availability of this coherent data base allowed interpretation of the evolution of intermetallic compound (IMC) formation in terms of interface thermodynamics and interdiffusion kinetics. On this basis spontaneous Sn whiskering on the surface of the Sn coating as a consequence of intermetallic phase (Cu6Sn5) formation along, specifically, Sn grain boundaries intersecting the Sn/Cu interfaces could be discussed. Moreover, a treatment to mitigate spontaneous Sn whiskering on the basis of thermodynamic control of the IMC morphology was proposed.

Keywords

Crystal growthFilamentaryMicrostructure

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Type
Articles
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Journal of Materials Research , Volume 26 , Issue 12 , 28 June 2011 , pp. 1482 - 1493
Copyright
Copyright © Materials Research Society 2011

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