Failure modes of tantalum capacitors made by different technologies

Abstract

Tantalum capacitor failure modes have been discussed both for the standard manganese dioxide cathode and the new conductive polymer (CP) type. For standard tantalum in the normal operation mode, an electrical breakdown can be stimulated by an increase of the electrical conductance in channel by an electrical pulse or voltage level. This leads to capacitor destruction followed by thermal breakdown. In the reverse mode, we have reported that thermal breakdown is initiated by an increase of the electrical conductance by Joule heating at a relatively low voltage level. Consequently, a feedback cycle consisting of temperature–conductivity–current–Joule heat–temperature, ending with electrical breakdown was created. Both of these breakdown modes possess a stochastic behavior and can be hardly localized in advance. CP capacitors have shown a slightly different current conductivity mechanism compared to standard tantalum capacitors. The breakdown of CP dielectrics is similar to avalanche and field emission breaks. It is an electromechanical collapse due to the attractive forces between electrodes, electrochemical deterioration, dendrite formation, and so on. However, some self-healing of the cathode film has been reported. This can be attributed to film evaporation, carbonizing or reoxidation. Not all of the breakdowns of CP capacitors can lead to self-healing or an open circuit state. Short circuits can also occur.