Failure Analysis Of Fixed Ceramic Capacitors

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Failure Analysis Of Fixed Ceramic Capacitors

Six (6) capacitors were received after board/system failure. All six (6) caps exhibited extensive fractures in the ceramic body. This analysis is to determine the point/cause of failure.

Sample caps were received for examination in the tape/reel form. After pick and place, followed by board processing and subsequent removal, all samples were examined and found to be free of fractures.

Ten (10) samples (tape and reel) were metallurgically prepared for cross sectioning to allow detailed microscopic examination of the internal plates and dielectric. It was determined that these components contain a dielectric thickness of .5 mils. This results in a susceptibility to micro voids in the dielectric. Of the 10 devices sectioned, 2 (20%) exhibited voids in the dielectric that would be considered a reliability risk per EIA-469-B.

Cross sectioning has shown that no micro fractures were induced by pick and place. Additional Micro sectioning of a failed capacitor indicates that this device failure may be the result of Electrical Overstress. The capacitor plates appear overheated, with metal and ceramic reflow and no apparent manufacturing induced defects. This would indicate that the capacitor was "overworked" electrically during application.

Failed device showing fractures in the ceramic body (50X).

Tape/reel device showing no defects (50X).

Overall X-section showing typical device (50X).

Detailed X-section showing the first of two voids (400X).

Detailed X-section showing the second of two voids (400X).

Detailed X-section showing the overstress site.

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