Nonlinear acoustic crack detection in thermoelectric wafers
Abstract
An acoustic technique for detecting cracks in bismuth telluride (Bi2Te3) thermoelectric wafers is presented. The technique is based on mechanically exciting the wafers with a low frequency pump signal that drives a crack to "breathe" by opening and closing periodically and a high frequency probe signal that interrogates the breathing crack. Interaction between the pump signal, the probe signal, and the crack leads to generation of acoustic nonlinearities in the wafer. In contrast to existing acoustic crack detection techniques we utilize standing waves within the wafers to facilitate simultaneous crack detection throughout the wafer, which reduces the total inspection time; we do not require uniform dimensions and material properties between wafers; and we do not affix the transmitter/receiver to the wafers, which can lead to wafer damage. We present a technique that integrates multiple damage metrics to identify cracks within the wafers. We demonstrate the technique on 94 Bi2Te3 wafers, of which we correctly identify cracked wafers with 4.3% total error and we correctly identify crack-free wafers with 7.5% total error. This acoustic crack detection technique finds application in manufacturing of thermoelectric wafers and other materials, where identifying cracks early in the manufacturing process results in significant time and cost savings. Additionally, this acoustic crack detection technique has implications for other nondestructive inspection applications where cracks cannot be detected effectively through existing techniques.
- Publication:
-
Mechanical Systems and Signal Processing
- Pub Date:
- May 2020
- DOI:
- 10.1016/j.ymssp.2019.106598
- Bibcode:
- 2020MSSP..13906598G
- Keywords:
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- Nonlinear acoustics;
- Nondestructive evaluation;
- Acoustic crack detection;
- Thermoelectric wafer testing