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| Old tantalum capacitors (solid type) Would you use them? |
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| Gyro:
I'm really not sure that dry solid Tantalum capacitors have a self healing mode. It's more a case of which weak spot fails first and whether there's enough thermal energy for it to propagate to device meltdown. Personally I have a theory that old non-hermetic bead tants suffer degradation due to moisture ingress in storage. It would certainly explain why so many have a tendency to fail in the hours and days after old equipment is powered up, when they presumably originally worked without problem for years. Hermetic axial dry (and wet) tants seem to last for ever. |
| T3sl4co1l:
Yeah, that would support the idea of reforming. Appnotes, at least, describe the process as: a momentary short, causing the MnO2 electrolyte to heat up and decompose to Mn2O3, an insulator. The permeability of MnO2 for H+, OH- or H2O is probably not nonexistent, and that would have some relevance in storage. A precaution might then be to treat them like moisture-sensitive SMDs: bake at elevated temperature before applying power. This should be measurable as an increase in the reforming voltage... unless the thermal cycling itself causes more trouble. Tim |
| coppercone2:
would you bake, cool down, then power, or would you bake, power, turn off heat, then slowly decrease current to cool it down? if something is reforming, I get the idea its like, squishy or plasticky or something, so it might work better if its warm to start with, if stuff has to migrate around with less stress.. i.e. gas diffusion might be higher in hot parts so there is less pressure build up |
| Conrad Hoffman:
If I see any measurable noise caused by a tantalum cap, it goes straight to the bin. Ditto for DC leakage anywhere near the datasheet values. |
| SilverSolder:
The "sudden failure" mechanism of tantalum capacitors is referred to as Field Crystallisation in this paper: https://www.researchgate.net/publication/27357654_Failure_Mechanism_of_Solid_Tantalum_Capacitors This paper seems to indicate that field crystallisation requires a voltage to be applied in order to happen. - This sounds like good news for anyone with a stash of old tantalum caps! |
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