Acoustic Detection of Cracks and Delamination in Multilayer Ceramic Capacitors

Abstract

Multilayer ceramic capacitors (MLCC) are the most widely used capacitor type in the electronics industry. However, the brittle ceramic dielectric makes MLCCs prone to mechanical damage. Manufacturing defects or damage during board assembly may cause a capacitor to prematurely fail during its operational life. Here, we demonstrate the fast and non-destructive acoustic screening of MLCCs. Soldered 2220-sized MLCCs were subjected to ac voltage frequency sweeps, causing them to vibrate mechanically. Acoustic responses of the capacitors were measured before and after subjecting the test circuit board to severe bending. The results show that the cracks and delaminations caused by bending induce characteristic changes in the capacitors' acoustic response. A support vector machine classifier was trained to successfully detect damaged capacitors based on their acoustic response. Index Terms-Acoustic emission, ceramic capacitors, nondestructive testing. I. INTRODUCTION M ULTILAYER ceramic capacitors (MLCCs) are commonly used in the electronics industry [1]. The ceramic dielectric gives MLCCs high capacitance per volume, but also makes them prone to mechanical damage. Voids and delaminations are typical manufacturing defects in MLCCs, often related to thermal stresses [2], [3]. Mechanical stress, such as improper printed circuit board (PCB) handling during assembly, can lead to cracks or delamination in MLCCs [4], [5]. Mechanical damage in MLCCs is often left unrecognized during production or assembly, as the capacitor may operate normally electrically. However, in the field, a crack or delamination in an MLCC may grow in size, resulting in loss of Manuscript

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