An AC-voltage-induced acoustic emission test technique for screening physical flaws, particularly delaminations, in various Z5U and X7R/BX ceramic capacitors was extensively evaluated. The test results showed that the severity of delaminations strongly coincided with the corresponding degree of severity in the acoustic signal. This led to a ten-times-higher rejection rate against the ceramic capacitors with delaminations in most of the screening tests. The source of acoustic waves was attributed to the partial discharge in delaminations, cracks, and pores due to the field intensification by the high-K dielectric materials. Almost identical patterns of behavior were found for acoustic emission and partial discharge with respect to the application of voltage and the chance of dielectric material.
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