Gideon Analytical Laboratories received 100 capacitors and directed to analyze them via cross-sectional analysis. Capacitors store charges and frequently appear on PCBs. There are many types of capacitors; electrolytic capacitors are tantalum capacitors are fairly common. The goal was to discover any abnormalities or determine if there were no abnormalities.
Each capacitor was cross-sectioned and observed 15 to 20 times under 40-72x magnification during the sectioning process. At some point during the cross-sectioning process, pictures were taken to depict the internal quality of the ceramic structure and any cracks (mechanical, knit, Kirkendall voiding or other defects) that may be present.
Out of 100 capacitors, two were found to be defective with mechanical cracks in the terminal area. The first is pictured at the top left. This capacitor failed the IR reading with excessive leakage current when trying to charge the capacitor. All cracks were in the terminal area on only one side. The two observed cracks were in the terminal area under the solder fillet. Both cracks were on capacitors in the C4 position. The crack on the second capacitor is pictured at the top right.
C4 capacitor crack may be caused by a PCB twisting action as opposed to a PCB flexing issue. The cracks disappeared about one-third through the cross-section. When the cracks disappeared from the cross-section, the capacitor recovered from excessive leakage current. This is normal. Terminal cracks are the most common failure mode on MLCC failures.
Failure analysis provided by Gideon Analytical Laboratories can be customized to fit a company’s specific needs and priorities. Failure analysis can be preventative in nature as well as diagnostic. Electronics companies can use Gideon Analytical Laboratories simply to make sure their devices have integrity and are functioning properly. Electronics companies can also use Gideon Analytical Laboratories to find the cause of failures. Either way, the primary goal of Gideon Analytical Laboratories is to help electronics companies save time, save money, and better prepare for the future.