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.
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Thanks,
- Win
Very bad! It will instantly short circuit the solar panels draining the sun dry of light and ending all life on earth!
Seriously, not much.
piglet
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.
mandag den 20. august 2018 kl. 21.54.18 UTC+2 skrev Winfield Hill:
wasn't it Larkin that tried 100s of volt on similar caps with no ill effect?
Protect it with a zener diode.
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.
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Thanks,
- Win
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.
-- John Larkin Highland Technology, Inc picosecond timing precision measurement jlarkin att highlandtechnology dott com http://www.highlandtechnology.com
You're familiar with the old "noise-emitting diode" data sheet? Maybe a bit like that. :-)
So what happens when you over voltage C0Gs?
George H.
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.
Tim
-- Seven Transistor Labs, LLC Electrical Engineering Consultation and Design Website: https://www.seventransistorlabs.com/
I assume that C stays pretty constant until they actually fail. So maybe their voltage rating is more realistic than for hi-K dielectrics.
-- John Larkin Highland Technology, Inc lunatic fringe electronics
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?
Rick C.
Is there anything combustible in a MLCC? John
Judging by the manufacturers' C(V) curves, quite a few part numbers share the same physical device.
Cheers
Phil Hobbs
That's cheating.
-- John Larkin Highland Technology, Inc lunatic fringe electronics
Intel does it with their CPUs. Why not their suppliers too? [Ceramic caps are used for interposer bypass.]
Tim
-- Seven Transistor Labs, LLC Electrical Engineering Consultation and Design Website: https://www.seventransistorlabs.com/
Yes. Electricity. :^)
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.
Tim
-- Seven Transistor Labs, LLC Electrical Engineering Consultation and Design Website: https://www.seventransistorlabs.com/
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
and afaiu mounted at 90 degrees to reduce the risk both will crack
See e.g. this comparison of Kemet 4.7 uF 0805s, 10V vs 16V:
Cheers
Phil Hobbs
-- 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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