The previous post reminded me:
I've started using polymer aluminum caps, the United Chem-Con surface-mount ones. They seem ideal: very low esr, no explosive mechanism, potentially long life, cheaper than tants, and capacitance holds up at -40C.
I tested a couple of 100 uF, 16 volt parts. Forward leakage is low, reverse leakage similar or a bit less than a wet lytic.
I slowly increased the voltage and, unlike a wet cap, the leakage didn't go up much. At about 35 volts, it suddenly failed shorted, which seems fair to me.
Pretty good so far. Anybody got experience or advice about these things?
I've read that moisture may degrade the polymer, and cause a loss of capacitance over time, but I don't know the numbers. So I guess it's prudent to overkill a lot on capacitance, which is generally easy, since they are pretty dense.
John