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Interface structure and strength of ultrasonically wedge bonded heavy aluminium wires in Si-based power modules

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Abstract

In this paper the microscopical structure of wedge bonded interfaces is investigated, with a focus on what effect the power in the ultrasonic bonding and the initial microscopical structure of the \(Al\) wire have on the quality of the bonding. The quality evaluation is based on mapping the microscopical restructuring of the wire grains during bonding and thereby assessing the effective bonding area. Three approaches are utilized in the interface characterization: mechanical shear test, optical microscopy combined with micro-sectioning, and scanning electron microscopy assisted by focused ion beam milling. The shear test is applied to quantify the strength of the bonded interfaces, while the other methods are used to map the grain reconstruction caused by the bonding. From the results it is possible to map a 3D image of the wire deformation, and the grain refinement region which is the dominating parameter with respect to fatigue related cracking of the interfaces. It is found that the bonding power, as well as the initial wire structure directly affects the refinement region and thereby the strength of the interface.

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Acknowledgments

The work is a part of the Center of Reliable Power Electronics (CORPE) funded by the Danish Strategic Research Council. A special thanks is attributed to Kim Houtved Jensen and Dorthe Rasmussen for assistance with sample preparation.

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Authors and Affiliations

  1. Department of Physics and Nanotechnology, Aalborg University, Skjernvej 4A, 9220, Aalborg Øst, Denmark

    Kristian Bonderup Pedersen, Peter Kjær Kristensen, Vladimir N. Popok & Kjeld Pedersen

  2. Danfoss Silicon Power GmbH, Husumer Strae 251, 24941, Flensburg, Germany

    David Benning

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  1. Kristian Bonderup Pedersen
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  2. David Benning
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  3. Peter Kjær Kristensen
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  4. Vladimir N. Popok
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  5. Kjeld Pedersen
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Correspondence to Kristian Bonderup Pedersen.

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Pedersen, K.B., Benning, D., Kristensen, P.K. et al. Interface structure and strength of ultrasonically wedge bonded heavy aluminium wires in Si-based power modules. J Mater Sci: Mater Electron 25, 2863–2871 (2014). https://doi.org/10.1007/s10854-014-1953-8

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  • DOI: https://doi.org/10.1007/s10854-014-1953-8

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