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

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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.

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Acknowledgments

The authors are much obliged to the company “Hans Heimerdinger Oberflächentechnik” in Pforzheim, Germany for specimen preparation. The authors would also like to thank Mrs Ulrike Eigenthaler (Max Planck Institute for Metals Research, Stuttgart) for preparing cross-sectional lamellae, by means of FIB, suitable for TEM analysis and Dr. Ewald Bischoff (Max Planck Institute for Metals Research, Stuttgart) for performing the TEM investigations.

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Authors and Affiliations

  1. Max Planck Institute for Metals Research, D-70569, Stuttgart, Germany

    Matthias Sobiech, Udo Welzel, Jiang-Yang Wang & Eric Jan Mittemeijer

  2. Robert Bosch GmbH, D-72770, Reutlinge, Germany

    Matthias Sobiech & Werner Hügel

  3. Institute for Materials Science, University of Stuttgart, D-70569, Stuttgart, Germany

    Carmen Krüger & Eric Jan Mittemeijer

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  1. Matthias Sobiech
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  2. Carmen Krüger
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  3. Udo Welzel
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  4. Jiang-Yang Wang
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  5. Eric Jan Mittemeijer
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  6. Werner Hügel
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Correspondence to Jiang-Yang Wang.

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Sobiech, M., Krüger, C., Welzel, U. et al. Phase formation at the Sn/Cu interface during room temperature aging: Microstructural evolution, whiskering, and interface thermodynamics. Journal of Materials Research 26, 1482–1493 (2011). https://doi.org/10.1557/jmr.2011.162

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