Acoustic detection of cracks and delamination in Multilayer Ceramic Capacitors

Abstract

Multilayer ceramic capacitors (MLCC) are the most 5 widely used capacitor type in the electronics industry. However, 6 the brittle ceramic dielectric makes MLCCs prone to mechanical 7 damage. Manufacturing defects or damage during board assembly 8 may cause a capacitor to prematurely fail during its operational 9 life. Here, we demonstrate the fast and non-destructive acoustic 10 screening of MLCCs. Soldered 2220-sized MLCCs were subjected 11 to ac voltage frequency sweeps, causing them to vibrate mechan-12 ically. Acoustic responses of the capacitors were measured before 13 and after subjecting the test circuit board to severe bending. The 14 results show that the cracks and delaminations caused by bending 15 induce characteristic changes in the capacitors' acoustic response. 16 A support vector machine classifier was trained to successfully 17 detect damaged capacitors based on their acoustic response. 18 Index Terms-Acoustic emission, ceramic capacitors, nonde-19 structive testing. 20 I. INTRODUCTION 21 M ULTILAYER ceramic capacitors (MLCCs) are com-22 monly used in the electronics industry [1]. The ceramic 23 dielectric gives MLCCs high capacitance per volume, but also 24 makes them prone to mechanical damage. 25 Voids and delaminations are typical manufacturing defects in 26 MLCCs, often related to thermal stresses [2], [3]. Mechanical 27 stress, such as improper printed circuit board (PCB) handling 28 during assembly, can lead to cracks or delamination in MLCCs 29 [4], [5]. Mechanical damage in MLCCs is often left unrec-30 ognized during production or assembly, as the capacitor may 31 operate normally electrically. However, in the field, a crack or 32 delamination in an MLCC may grow in size, resulting in loss of 33

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.…”

“…Usually, some data training algorithms are used to distinguish the damaged and undamaged capacitors. In [112], an acoustics detection based method is applied to detect the micro-crack of capacitors, as shown in Fig. 4…”

“…(d) Thermography and X-ray image of a failure MLC-Cap [113]. (e) Acoustic response of a failure MLC-Cap [112]. (f) SVM classifier fitted into observed MLC-Cap features [112].…”

“…(e) Acoustic response of a failure MLC-Cap [112]. (f) SVM classifier fitted into observed MLC-Cap features [112].…”

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

“…However, while the acoustic emissions carry information about the structural condition of a capacitor, the signs of damage can be hard to detect. The amplitudes and frequencies of the mechanical resonances exhibited by MLCCs show variation even between intact components, and although mechanical damage often manifests as new resonant peaks, such peaks do not always appear [23]. Moreover, factors such as electromagnetic interference and variations in the mechanical contact between the sensor and the capacitor can cause artifacts that could be misinterpreted as signs of damage.…”