Gideon Analytical Laboratories received several T491D475K050AT Kemet tantalum capacitors for electronic failure analysis. A capacitor is a passive two-terminal electronic component that stores electrical energy in an electric field. While some capacitance exists between any two electrical conductors in proximity in a circuit, a capacitor is a component designed to add capacitance to a circuit. The Kemet T491D475K050AT has a capacitance of 4.7 uF, a voltage rating of 50 VDC, and a tolerance of 10%, measures 7.3mm x 4.3mm x 3.1mm (LWH), has a minimum operating temperature of -55 degrees Celsius and a maximum operating temperature of 125 degrees Celsius. One of these capacitors had already been tested and found to be a dead short. The other capacitors were to be used to determine whether acid had affected the forming voltage oxide.
We conducted failure analysis on the T491D475K050AT Kemet tantalum capacitors. Sample 1 was examined; there was no external damage to the plastic or broken leads. Electrical testing confirmed a dead short. The plastic was then removed. The failure site showed fused tantalum, silver, and manganese dioxide all welling up from a cauldron looking depression. SEM-EDS analysis was then used to get reveal the elemental makeup the materials at the failure site. The SEM-EDS analysis revealed tantalum, manganese, silver, and some other elements. But there were no contaminating elements present at the failure site. We continued the SEM-EDS analysis, on different sections of the failure site but we did not find any foreign elements. We compared the failed T491D475K050AT Kemet tantalum capacitors and the good ones. We concluded that this failure was not related to contamination during the manufacturing process. The failure was an application issue caused by high voltage.
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