Comparison between piezoelectric method and ultrasonic signal analysis for crack detection in type II multilayer ceramic capacitors
✍ Scribed by Y. Ousten; S. Mejdi; L. Bechou; B. Tregon; Y. Danto
- Publisher
- John Wiley and Sons
- Year
- 1998
- Tongue
- English
- Weight
- 130 KB
- Volume
- 14
- Category
- Article
- ISSN
- 0748-8017
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✦ Synopsis
In this paper we present a comparison between two non-destructive techniques for crack detection in MLCCs. First, if a type II MLCC is biased with a DC field, the capacitor becomes temporarily 'poled' and can act as a transducer. This is induced by a residual piezoelectric effect used in the impedance spectroscopy method. Second, we used a scanning ultrasonic system working in the 10-100 MHz frequency bandwidth. To understand the ultrasonic signature, we used time-of-flight (TOF) detection with short-time Fourier transform (STFT) analysis to determine the depth and nature of defects with high accuracy. An application of digital signal processing to the characterization of defects is presented for a lot of MLCCs with cracks defects. For comparison, the same lot was tested with the piezoelectric method. The two techniques are closely correlated.