Leakage Current from MLCC on PCB

Gideon Analytical Laboratories received one failed multilayer ceramic capacitor (MLCC) on a printed circuit board (PCB). Multilayer ceramic capacitors are fixed value capacitors in which ceramic the material acting as the dielectric. It is made up of two or more alternating layers of ceramic and a metal layer acting as the electrodes. There are various types of materials that could function as the dielectric in a capacitor, for example, glass, porcelain, paper, or mica. No electrical information was supplied.

Failure analysis was conducted on the MLCC. The MLCC had no mechanical marks that would suggest mishandling. The MLCC has so much leakage current the capacitor would not charge. The MLCC was cross-sectioned to determine the cause. During the cross-sectioning, a crack in the margin was discovered. At some point, these cracks bisected the electrode, causing a short. The cracks were caused by PCB flexing or bending in one direction or another. The flexing allowed a crack to transgress both electrodes causing a short which lead to a failure site.

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crack from EOS

Crack caused by PCB flexing

MLCC on PCB

MLCC on PCB

Start of cross section

Start of cross section

Top of MLCC had no mechanical marks

Top of MLCC had no mechanical marks