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The Failure Of Tantalum Capacitor
Oct 30, 2016


 1. The tantalum capacitor because of "breakdown" constantly "self-healing" constantly failure problem.In normal use after a period of time often happen solid tantalum cap seal solder melts, or see, flying about solder on PCB.Analysis because of its "breakdown" and "self-healing" at work, in the repeated, has led to an increased leakage current.Such a short period of time (ns - ms) local short circuit, and through "self-healing" to return to work after. 
About the "healing".The ideal Ta2O5 dielectric oxide film is continuity and consistency.Combined with voltage or work under the high temperature, because of the existence of TA + ion defect micro defects lead to the leakage current increases, the temperature can reach above 500 ℃ ~ 1000 ℃.Such a high temperature makes the MnO2 back into low-cost Mn3O4.Some test of Mn3O4 resistivity is higher than that of MnO2 4 ~ 5 orders of magnitude.In close contact with Ta2O5 dielectric oxide film of Mn3O4 electrical isolation effect, to prevent further damage Ta2O5 dielectric oxide film, which is the local "self-healing" of tantalum capacitor.But, once again, probably in the next "breakdown voltage" will "breakdown" than the previous lower voltage.After each breakdown, the leakage current will increase, and the breakdown power level ampere current may be produced.At the same time, the stored energy of the capacitor itself is very big, cause the capacitor permanent failure.
 


2. The tantalum capacitor "cause the failure problem?"

Solid tantalum Ta2O5 dielectric oxide film has a one-way conductive performance, when there is a charge amplifier current through Ta2O5 dielectric oxide film, can cause heating failure.No charge amplifier current, dielectric oxide thin fairly stable, micro ion arrangement is irregular, disorderly, called amorphous structure.The color of the visual rendering is colorful interference color.When the amorphous structure to the structure of the setting, and gradually become orderly arrangement, called the "crystallization", presented in a visual color is no longer a multicoloured interference color, but without luster, darker color.Ta2O5 dielectric oxide film "crystallization" of evacuation structure leads to the deterioration of the tantalum capacitor performance until the breakdown failure.
 


3. The tantalum capacitor "field failure" problem
Tantalum capacitor with high voltage, high electric field is formed within, easy to local breakdown.
Breakdown accident rate reduced to a stable value over time.When the breakdown voltage is close to an increased incidence of breakdown.As the growth of the voltage, the device for thermal runaway in a defect and the probability of failure also increases.The breakdown voltage depends on the pulse of continuous.In some experiments, you can see the breakdown voltage and decreased with the increase of the length of the pulse.The process is not very sure;Breakdown in uncertain interval in position.In the mode, the electric breakdown was due to the joule heat generated by the thermal breakdown of the final state.
 
Capacitance if improper selection, when capacitance failure after short circuit, in general, there are two to consider, as a manufacturer, if must be after failure is open circuit state, consider the internal fuse series, through the voltage and current are tantalum capacitor inside the fuse.So it expires is an open mode, and customers in the selection of the time, must take into account enough margin in the inside, if used in normal working voltage is very reliable.
Voltage in the industrial electronics, automotive electronics, at least need derating 50% use.
 
Another wet it has a great change to the capacitance of the ESR.