Lock-in Thermography Failure Detection on Multilayer Ceramic Capacitors After Flex Cracking and Temperature–Humidity–Bias Stress

Abstract

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.

An Overview of Condition Monitoring Techniques for Capacitors in DC-Link Applications

“…3(b) lists some commonly used parameter acquisition methods. It is found that industrial instruments including weighting meters [108], [109], X-ray image meters [110], optical inspection meter [111], acoustic detection meter [112], thermography meter [113], etc., are widely used to obtain non-electrical parameters. Moreover, internal temperature sensors [114] and internal pressure sensors [115] are employed to obtain the internal temperature and pressure of capacitors.…”

“…(c) X-ray images of a healthy Al-Cap and a failure Al-Cap [109]. (d) Thermography and X-ray image of a failure MLC-Cap [113]. (e) Acoustic response of a failure MLC-Cap [112].…”

Lock-In Thermal Test Simulation, Influence, and Optimum Cycle Period for Infrared Thermal Testing in Non-Destructive Testing

“…The usage of (a) flash, (b) transient, or (c) lock-in thermography has been used by Stoynova to study the shape and better understand their root cause [ 22 , 23 ]. Other similar and relevant works, even if not using simulations but focusing on laboratory tests, were presented by Breitenstein [ 24 ], Brand [ 25 ], Andersson [ 26 ], Leppänen [ 27 ], and Hovhannisyan [ 28 ].…”

Nondestructive Acoustic Testing of Ceramic Capacitors Using One-Class Support Vector Machine With Automated Hyperparameter Selection

“…On the other hand, if a crack or delamination resides in the passive region of the MLCC or at the solder joints, the electrical operation of the component is likely to remain unaffected at first [10]. However, the damaged location may grow in size over time, leading to a reduced capacitance, open-or short-circuit [11], or deterioration of the dielectric material as moisture gets inside the capacitor [12], [13]. While the probability of failure for a single capacitor is very low, capacitor failures contribute to a significant fraction of faults in the field owing to the high number of components that are used [4].…”