Characterization of Electrical-Thermal-Mechanical Deformation of Bonding Wires under Silicone Gel Using LF-OCT

Zhiyi Zhao, Zijian Zhang, Samuel Lawman, Zhihao Yin, Yihua Hu, Ju Xu, Yaochun Shen*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review


Bonding wires are one of the most failure-prone components of power electronics' modules, and silicone gel is usually employed to encase bonding wires. To study the deformation of silicone gel-encased bonding wires, in this article, we report the use of line-field optical coherence tomography (LF-OCT) technique to precisely measure the electrical-thermal-mechanical (ETM) deformation of bonding wires. An LF-OCT system was developed to capture the whole cross-sectional image (B-scan) of the bonding wire sample in a single-shot fashion due to its advantageous parallel detection scheme. This, together with the Fourier phase self-referencing technique, allows the deformation of the bonding wires to be quantitatively measured down to the range of 0.1 nm. The maximum sampling rate (framerate) of the deformation measurement achieved was 400 Hz when setting camera imaging size to 1920 × 200 pixels, providing a temporal resolution of 2.5 ms for monitoring the ETM deformation dynamics of the bonding wire. We found that the ETM deformation of the gel-encased bonding wire was about three times smaller than that of the bare bonding wire. These results represent the first experimental demonstration that the LF-OCT could be a useful analytical tool for studying the time-dependent ETM deformation of bonding wires encased by silicone gel.

Original languageEnglish
Article number9384327
Pages (from-to)11045-11054
Number of pages10
JournalIEEE Transactions on Power Electronics
Issue number10
Publication statusPublished - 23 Mar 2021

Bibliographical note

Funding Information:
Manuscript received October 9, 2020; revised February 20, 2021; accepted March 11, 2021. Date of publication March 23, 2021; date of current version June 30, 2021. This work was supported in part by the Royal Society Newton Advanced Fellowship (NAF\R2\180578), in part by the Royal Society Industry Fellowship (INF\R1\201021), and in part by the Engineering and Physical Sciences Research Council under Grant EP/R014094/1. Recommended for publication by Associate Editor K. Ngo. (Corresponding author: Yaochun Shen.) Zhiyi Zhao, Zijian Zhang, Samuel James Lawman, and Yaochun Shen are with the Department of Electrical Engineering and Electronics, University of Liverpool, Liverpool L69 3GJ, U. K. (e-mail: [email protected]; [email protected]; s.lawman@liverpool.; [email protected]).

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  • Bond wire reliability
  • electrical-thermal-mechanical (ETM) deformation
  • line-field optical coherence tomography (LF-OCT)
  • silicone gel

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