What do you think will happen if the data-sheet's rated voltage for a ceramic capacitor is exceeded? E.g., Kemet C0805C105J4RAC, an 0805 X7R 1.0uF 16V type; could see 18.6V from a solar-cell panel.
From what I've seen in other ceramics - there's a loss in capacitance (it's likely already down to 0.5uF or less at rated voltage). Don't know if MTBF suffers. I've never witnessed anything catastrophic.
Better yet, I've changed it to an 0805 1uF 35V part. (Thankfully, a set of 8 boards not yet deployed.) A Murata GCM21 X7R part, drops to 0.75uF at 18V.
3x overvoltage seems safe for most ceramic caps. I've tried 16 volt caps at 120v, and they were OK. The voltage rating is based mostly on capacitance loss, I think, except for C0Gs.
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John Larkin Highland Technology, Inc
picosecond timing precision measurement
jlarkin att highlandtechnology dott com
http://www.highlandtechnology.com
No, not at all, and definitely don't fool yourself that that's how they rate them!
I've seen X7Rs with from 70% to 10% of rated value, at rated voltage.
As far as I know, the voltage rating is a minimum breakdown. And typical breakdown seems to be a generous factor above that (someone should do statistics on it).
Type 2 ceramics are no better than ferrite beads. The impedance and rating have _absolutely nothing_ to do with each other, and if things sometimes seem to be some way, it's utter coincidence.
I've never tried to find the breakdown voltage of caps, but I've seen MLCCs that shorted, caught file and burned holes in the boards. Was that a manufacturing defect rather than an over voltage breakdown?
Usually it's a crack that brings the layers together (shorted), or at least introduces an airgap with much lower breakdown, to the same end. End result is arcing and melted ceramic, along with anything else nearby, usually charred substrate.
The automotive guys put two in series for this reason, it's safer.
afaiu part of the current shortage is manufacturers trying get rid of the many parts that are basically the same and reduce the number of different packages
See e.g. this comparison of Kemet 4.7 uF 0805s, 10V vs 16V:
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Cheers
Phil Hobbs
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Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC / Hobbs ElectroOptics
Optics, Electro-optics, Photonics, Analog Electronics
Briarcliff Manor NY 10510
http://electrooptical.net
http://hobbs-eo.com
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