Ceramic caps from China - Page 1
Forum section: electronics / beginners

author: Discotech
author_rank: Regular Contributor
timestamp: August 17, 2018, 08:49:27 pm
content: Some of the caps I've been testing today have been way out of tolerance1nF = 1.4nF4.7nF = 6.8nF150pF = 100pF100nF = 50nF1.5nF = 2nFthe other 70% of the bundle were within toleranceBut I don't understand how these ones can be so far out they're in the next or previous band, is it an issue when the numbers are printed on them and they get the wrong ones printed ? Is this common with caps from China ? Better to buy from Farnell/Mouser if you want better accuracy I guess ?

author: homebrew
author_rank: Frequent Contributor
timestamp: August 17, 2018, 09:17:51 pm
content: What is the exact specification of the capacitors?How did you measure the capacitance?Generally speaking, I would ONLY buy from reliable sources anyway.That said, many reliable electronic parts are manufactured in China ... So rather your specific source than the country of origin would be the issue ...

author: Discotech
author_rank: Regular Contributor
timestamp: August 17, 2018, 09:28:15 pm
content: Quote from: homebrew on August 17, 2018, 09:17:51 pmThe numbers on left were supposed specified values, with the numbers on the right being what they were closer toUsed both my DMM and GM328 Tester on the first few as I was thinking it was possibly mistaken calibration on the tester but when the DMM was showing pretty much identical values I figured it must be the caps that have incorrect numbers printed on themI'm not too fussed as they were cheap from aliexpress, it was like £1 for 300 and the majority were within spec but the ones out of spec were way out so I was wondering if it's a common issue ?

author: bson
author_rank: Unknown
timestamp: August 17, 2018, 09:38:55 pm
content: The tester may not have any accuracy to speak of at such small values.What is the dielectric class and voltage rating? Maybe they're derated for a higher voltage than the tester uses.

author: floobydust
author_rank: Super Contributor
timestamp: August 17, 2018, 09:39:12 pm
content: I too find the cheapola cap values are all over the place. Expensive parts are all about -15% and vanilla parts are +/-30% of rated value.

author: Discotech
author_rank: Regular Contributor
timestamp: August 17, 2018, 09:57:47 pm
content: Quote from: bson on August 17, 2018, 09:38:55 pm50v X7Tester only uses 9v

author: T3sl4co1l
author_rank: Super Contributor
timestamp: August 18, 2018, 12:06:20 am
content: Nice thing about caps is they are almost never labeled, so you can "counterfeit" by merely swapping labels on the reel, or stock numbers even.Ditto for voltage. You could get an 0805 10nF that's 16V (contains a few very closely spaced plates, and a lot of unused ceramic), or 100V+ (the entire height is filled by more, and widely spaced, plates). No idea until you do a C(V) test.Tim

author: LukeW
author_rank: Frequent Contributor
timestamp: August 18, 2018, 10:09:28 am
content: What is the specified tolerance of the caps you ordered?What’s the dielectric type you ordered?What is the rated voltage of the cap and what voltage are you measuring the capacitance at? What temperature?It is not yet clear that you did not get what you asked for.

author: wraper
author_rank: Unknown
timestamp: August 18, 2018, 10:18:44 am
content: Is this an SMD capacitor assortment? Most likely they were just mislabeled.

author: ocset
author_rank: Super Contributor
timestamp: August 18, 2018, 10:20:51 am
content: I think what you got sounds ok...if you want accuracy in ceramic, you need C0G dielectric

author: iMo
author_rank: Super Contributor
timestamp: August 18, 2018, 10:22:41 am
content: I got a shortwave cw transceiver kit ($18) from China, and ALL the ceramic (small brown discs) capacitors were around 50-100% off. They were labeled with the value. Thus I replaced all the caps and resistors and it worked fine.

author: wraper
author_rank: Unknown
timestamp: August 18, 2018, 10:22:57 am
content: Quote from: treez on August 18, 2018, 10:20:51 amIt's not, and 150pF most likely would be C0G anyway. Also very unlikely that type 2 and 3 ceramic caps would go that much upwards in their capacitance in any circumstances.

author: Discotech
author_rank: Regular Contributor
timestamp: August 18, 2018, 12:51:17 pm
content: Quote from: wraper on August 18, 2018, 10:18:44 amIt was these -https://www.aliexpress.com/item/Ceramic-capacitor-2PF-0-1UF-30-valuesX10pcs-300pcs-Electronic-Components-Package-ceramic-capacitor-Assorted-Kit-Free/32305092269.html

author: Old Printer
author_rank: Frequent Contributor
timestamp: August 18, 2018, 01:34:26 pm
content: I have read that "run of the mill" ceramic capacitors have a typical tolorence of -20% to +80%. I thought that was wacky, but have seen that in a few places. This was not in reference to any particular brand.

author: Audioguru
author_rank: Super Contributor
timestamp: August 18, 2018, 01:50:11 pm
content: Which is trustworthy? A Chinese capacitor with no-name-brand that was made by someone who knows little about capacitors and made by him in his basement? Or a capacitor made by a trusted international company in their factory in China? Their spec's and costs are a "little" different."Ali" companies are Chinese like "ebay". Who knows if they buy good stuff or junk. They both sell cheap stuff.

author: rstofer
author_rank: Super Contributor
timestamp: August 18, 2018, 07:33:45 pm
content: Here is a page from DigiKey - note that one category of tolerance is 0,+100%https://www.digikey.com/products/en/capacitors/ceramic-capacitors/60It could be that all of your capacitors are within that tolerance. The question is: what was the specified tolerance?The assortment only costs $1.40 USD so I wouldn't have high expectations.

author: wraper
author_rank: Unknown
timestamp: August 18, 2018, 08:02:57 pm
content: Quote from: rstofer on August 18, 2018, 07:33:45 pmI don't think it's possible to get 1-2n low voltage capacitors with super unstable Y5V, Z5U (type 3) ceramic. But it's quiet easy to check. Just hold a capacitor with fingers while measuring and capacitance should go down a lot due to heat transfer from fingers. Or heat some other way.

author: mzzj
author_rank: Super Contributor
timestamp: August 18, 2018, 08:10:57 pm
content: Quote from: wraper on August 18, 2018, 08:02:57 pmJust hold my beer:https://www.digikey.com/products/en/capacitors/ceramic-capacitors/60?k=&pkeyword=&pv14=20&pv14=32&FV=440003%2C44016e%2C44016f%2C440170%2C4401a2%2C440037%2C440006%2C440044%2C440045%2C440007%2C440055%2Cmu1000pF%7C2049%2Cffe0003c%2C380002%2C380014%2C380020&quantity=0&ColumnSort=0&page=1&pageSize=25

author: wraper
author_rank: Unknown
timestamp: August 18, 2018, 08:29:35 pm
content: Quote from: mzzj on August 18, 2018, 08:10:57 pmOnly one part number in stock and that junk costs $ 0.30, LOL. +-20%, though. I wonder who buys that junk at such price.

author: bd139
author_rank: Super Contributor
timestamp: August 18, 2018, 08:46:49 pm
content: Just a heads up on shitty ceramics. A few of the C0G's and X7R's I got from even "multicomp" brands were bags of lies. A bag of MLCC's I bought from China were 50% faulty.I only buy Vishay / Murata / Kemet stuff from main line distributors now. Costs a lot more but worth it.

author: Discotech
author_rank: Regular Contributor
timestamp: August 18, 2018, 09:33:33 pm
content: Quote from: rstofer on August 18, 2018, 07:33:45 pmI 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

author: bson
author_rank: Unknown
timestamp: August 18, 2018, 10:48:19 pm
content: Take a look at:https://en.wikipedia.org/wiki/Ceramic_capacitor#/media/File:MLCC-BME-NME-Kap-Spg-Kurve-engl.svgSo 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.

author: bson
author_rank: Unknown
timestamp: August 18, 2018, 10:52:20 pm
content: Put on your safety glasses and subject one to 50V to see what happens.

author: KE5FX
author_rank: Super Contributor
timestamp: August 18, 2018, 11:10:19 pm
content: 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...

author: floobydust
author_rank: Super Contributor
timestamp: August 19, 2018, 12:20:56 am
content: 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.

author: Ken Hahn
author_rank: Newbie
timestamp: August 19, 2018, 05:53:51 am
content: Ceramic caps from China do tend to vary quite a bit in my experience, but often there is no stated tolerance to begin with. I think the variance is more likely due to poor manufacturing processes rather than some master plan to defraud customers. Even the physical sizes in the same batch can be all over the map at times which is a good indication that their process controls are lacking.The MLCC type seem to generally be better quality than the cheaper standard disc type.I think China caps are fine for applications such as bulk bypass caps where values are not at all critical, but for any applications where the value or long-term stability is important I would recommend sticking with Kemet or a similar quality brand. But keep in mind that even with those, the run-of-the-mill parts are often +80%/-20% tolerance unless you pony up for the higher spec stuff.--- Ken

author: JS
author_rank: Frequent Contributor
timestamp: August 19, 2018, 06:30:35 am
content: I've bought one of those and came in without any marking on values, they were supposed to be some values out of the scale, all differents in tapes of 20. Ok, I removed one of each tape, measured and put the value on the tape for later use. There were all wrong as yours, some of them were replicated, so two tapes with the same value, of course some values missing, and some that weren't even close to any of the ordered values.Is what you get from china. Even worse, in the same box I ordered 1% TH MF resistors, a bunch of them with almost every E24 value, I got 5% carbon ones... SMD resistors, some sensors seems ok, I also ordered LEDs, diodes, a few ICs but I never got to test them out. Still open to ask for reposition but I just don't know if it's worth it.So, I do need to get some decent components assortments but I don't know where to get reasonable cheap but reliable components... Those folders Dave has are great but they look quite expensive just to have sitting around in case you need one of the batch. SMD passives in all the different sizes and values are impossible to have around, while fixing stuff in a location like mine that getting a component takes like a month or a 300km trip that's a pain, I know you can get away bodging a different size in the thing, but space or power rating are never fine with that.JS

author: james_s
author_rank: Super Contributor
timestamp: August 19, 2018, 07:22:40 am
content: I've observed this same thing. I have a fairly accurate LC meter and was surprised when I checked some capacitors from a kit of cheap Chinese ceramic caps. I had to go through the whole collection of certain values to find a few that were even close to the rating. I don't expect high precision but I do expected much better than +-50%.