Kemet T491C155M035AT Surface Mount Tantalum Capacitors

Gideon Analytical Laboratories received two surface mount T491C155M035AT Kemet tantalum capacitors with internal resistive shorts. These capacitors have standard capacitance tolerances of ±10% and ±20%, with an operational temperature -55°C to +85°C rated voltage and up to +125°C with voltage derating in applications utilizing recommended series resistance. They have low leakage and are ROHS compliant. The goal was to determine the reason for the failure.

There was no damage tothe external plastic encapsulation of the package to indicate mechanical stress, which would weaken the package integrity. No marks were found by pick and place. The lead frame was normal and provided good flexibility and strain relief as well as package adhesion as it entered the encapsulation. The capacitor is pictured at the top left.

A cross-section of the capacitor revealed no unusual anomalies where the failure site occurred. There was a breakdown in the manganese dioxides which lead to the short however, no contamination was found using SEM-EDS in dielectric cavities. The cross-sectioned capacitor is pictured at the bottom right. The failure was caused by electrical overstress (EOS) to the manganese dioxide. Gideon Analytical Laboratories recommended checking the surge current on gate input when hot swapping.

With failure analysis provided by Gideon Analytical Laboratories, companies in the electronics industry can know and understand exact reasons why electrical components fail. This type of information can save companies enormous amounts of time and money when planning for the future.

Mounting terminals under plastic encapsulation

Mounting terminals under plastic encapsulation

Cross section of tantalum capacitor showing internal structure

Cross section of tantalum capacitor showing internal structure