A non-destructive method using lock-in thermography to detect failures in multilayer ceramic capacitors is presented. The thermal response of new 25 V multilayer ceramic capacitors is compared to the thermal response of the same capacitors after insertion of flex cracks as well as after 24 and 96 hours of total exposure time to a temperature of 75 • C, 75% relative humidity, and 25 V bias. The thermal response was measured before the introduction of any flex cracks, as well as directly after flex cracks were inserted by bending the printed circuit board to 6000 µStr. No significant change was detected in the thermal profile upon introduction of flex cracks of which the presence was verified by X-ray imaging. After the multilayer ceramic capacitors were subjected to a total of 96 hours of temperaturehumidity-bias stress, a significant increase in leakage current could be detected as a hotspot in one of the initially 24 samples by lock-in thermography. The influence of the different parameters, such as lock-in frequency, bias voltage and measurement time, on the detectability of the hotspot is presented.

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