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Ceramic caps from China

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Discotech:

--- Quote from: rstofer on August 18, 2018, 07:33:45 pm ---Here is a page from DigiKey - note that one category of tolerance is 0,+100%

--- End quote ---

I don't understand though, do they not do much QA testing on them ?

Surely if you're making caps and you test a bunch and they turn out to be 100nF instead of the 50nF you were expecting it would be easier to just rate them at 100nF instead or do they test after the numbers have been printed and just say "fuck it" if it's nowhere near intended rating ?

+100% tolerance sure seems like a "fuck it" attitude from the manufacturer  :palm:

bson:
Take a look at:
https://en.wikipedia.org/wiki/Ceramic_capacitor#/media/File:MLCC-BME-NME-Kap-Spg-Kurve-engl.svg

So if you want 100nF for the particular BME X7R cap graphed at its rated 50V, it will need to be almost 200nF (maybe 180nF) at 10V.  Class 2 caps have very poor voltage linearity and are intended for bypass and supply filter uses, not resonant circuits...  Add to this the 15-20% (I forget off hand) tempco...  For the X7R's I think you probably got a reasonable product based on your measurements so far.

bson:
Put on your safety glasses and subject one to 50V to see what happens. :)

KE5FX:
It's almost unthinkable that people aren't relabeling MLCCs under the table, given how apocalyptically-f***ed the market is.  If you're a Chinese distributor with a warehouse full of 82 nF caps, and everybody wants 100 nF, well...

floobydust:
Just a note- capacitance meters can give confusing results.
It depends on the test voltages and firmware algorithm (single or dual-slope), because the voltage coefficient of capacitance and dielectric non-linearity can show up, more or less.

I'm wondering if the chinese are selling rejects (high/low out of tolerance) or they have poor quality control on the ceramic powders, or if these are from small ma and pa shops.
 

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