Degradation of Sn‐Ag‐Cu heat‐sink attachment during thermal shock cycling

Junling Chang (Shanghai Institute of Microsystem and Information Technology, Chinese Academy of Science, Shanghai, People's Republic of China DaimlerChrysler SIM Technology Co., Ltd, Shanghai, People's Republic of China)
Dirk Janz (DaimlerChrysler SIM Technology Co., Ltd, Shanghai, People's Republic of China)
W. Kempe (DaimlerChrysler Research Institute, Frankfurt, Germany)
Xiaoming Xie (Shanghai Institute of Microsystem and Information Technology, Chinese Academy of Science, Shanghai, People's Republic of China DaimlerChrysler SIM Technology Co., Ltd, Shanghai, People's Republic of China)

Soldering & Surface Mount Technology

ISSN: 0954-0911

Publication date: 1 December 2005

Abstract

Purpose

To investigate the degradation of lead free solder heat‐sink attachment by thermal shock. Samples with high voiding percentages were selected for the investigation in order to get information on the significance of voids on the reliability of Sn‐Ag‐Cu heat‐sink attachment.

Design/methodology/approach

Through the use of X‐ray, C‐mode scanning acoustic microscopy, dye penetration, cross section and scanning electron microscopy/energy‐dispersive X‐ray tests, the degradation of Sn‐Ag‐Cu heat‐sink attachment during thermal shock cycling was evaluated.

Findings

The results showed that the Sn‐Ag‐Cu heat‐sink attachment where the area of voiding was 33‐48 per cent survived 3,000 thermal shock cycles, although degraded. The main degradation mechanism for the solder attachment was not solder fatigue but interface delamination due to Kirkendall voids at the Cu/Cu3Sn interface. It was found that the large voids in the Sn‐Ag‐Cu heat‐sink attachment were not significantly affecting the solder joint lifetime. Big differences of intermetallic compound growth behaviour and Kirkendall voids at device/solder and solder/Cu pad interfaces are found and the reasons for this are discussed.

Originality/value

This work has clarified the general perception that large voids affect the thermo‐mechanical lifetime of solder joint substantially and also provides further understanding of the Sn‐Ag‐Cu heat‐sink attachment degradation mechanism.

Keywords

Citation

Chang, J., Janz, D., Kempe, W. and Xie, X. (2005), "Degradation of Sn‐Ag‐Cu heat‐sink attachment during thermal shock cycling", Soldering & Surface Mount Technology, Vol. 17 No. 4, pp. 10-16. https://doi.org/10.1108/09540910510630386

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Publisher

:

Emerald Group Publishing Limited

Copyright © 2005, Emerald Group Publishing Limited

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