Faulty name-brand ceramic capacitors - common? - Page 1
Forum section: electronics / projects

author: Corporate666
author_rank: Unknown
timestamp: October 13, 2017, 07:24:18 pm
content: I have experienced a 500% increase in failures in the field over the last few months for one specific product. I've gotten some of the units back and it was just this week I was able to go through all the failed units, do a thorough post-mortem and tabulate the results.It turns out a capacitor on the power input was failing as a dead short, causing the traces on the board leading to that cap to ultimately massively overheat and go up in smoke.The capacitors are CL21A226MOCLRNC from Samsung. I went through our stack of boards that failed post-assembly testing and were awaiting rework, and found that most of the failures there are also due to this same capacitor. I then went through the drop-bin on the pick and place machine (where it drops parts it could not place for whatever reason), and pulled out all of the aforementioned caps and tested them... about 5% were bad - just a dead short. I looked under a microscope and there's nothing unusual to see, no cracks or problems with the solder points or anything else.But the fact that I saw so many failed parts in the PnP reject bin tells me that it wasn't the reflow process, nor the testing process, nor the use in the field that was causing the issues... it was bad parts right off the reel.I was wondering if anyone has seen anything like this before? Digikey has ~200,000 of these caps in stock, so it seems to be a pretty common usage part, and I am very surprised that a major manufacturer would be shipping parts with this problem. But maybe I have just been lucky in the past?

author: georges80
author_rank: Frequent Contributor
timestamp: October 13, 2017, 08:28:15 pm
content: It's an MLCC - so likely internally shorted and likely due to an assembly issue or PCB layout issue (i.e. micro cracks leading to internal short).I'd find it hard to believe they are faulty right out of the chute... I'd pull a bunch of parts straight off the reel and measure/test before any pnp machine etc has gotten to them.IF you find them faulty on the reel then I would contact Digikey to figure out what is going on.cheers,george.

author: GreggD
author_rank: Regular Contributor
timestamp: October 13, 2017, 08:36:25 pm
content: Could someone be bending the pcb and causing micro cracks ?Is there a heavy component on the pcb so that if the pcb is picked up by one end the heavy part flexes the board.This is quite common and causes a dead or near dead short.

author: Leo Bodnar
author_rank: Frequent Contributor
timestamp: October 13, 2017, 09:01:17 pm
content: I have just ordered a few hundred from DK. Maybe I get lucky too - will let you know.I get ceramic caps failing shortcircuit now and then but they are usually already assembled and nowhere close to even 1%.Leo

author: wraper
author_rank: Unknown
timestamp: October 13, 2017, 09:26:02 pm
content: In my experience MLCCs fail because of mechanical stress. PCB may have 10s of the same ceramic capacitors on the single power rail, and it's always same single cap failing somewhere nearby to the mounting hole or board edge. Larger sizes are more susceptible.You won't see something like this unless cut capacitor in half.

author: wraper
author_rank: Unknown
timestamp: October 13, 2017, 09:31:25 pm
content: Quote from: Corporate666 on October 13, 2017, 07:24:18 pmI rather suspect PnP machine was smashing them while picking up or something like this. Are there multiple such capacitors on the PCB and only particular destinator failing?

author: Leo Bodnar
author_rank: Frequent Contributor
timestamp: October 13, 2017, 10:03:35 pm
content: I have seen capacitors with visible cracks and chips right off the  tape when I have been assembling prototypes manually.They were 1206 with high C / high V value for that package so not a cheapo 0.1uF runarounds. Can't remember exact brand but definitely well branded - TDK, Murata or Kemet.Anyone who worked in manufacturing will know that weird things do happen and when they do happen there are usually a lot of them.Leo

author: Corporate666
author_rank: Unknown
timestamp: October 13, 2017, 10:09:00 pm
content: Well, a plot twist... not all of the failed boards were PnP placed. The board doesn't have too many parts on it, so if the PnP is already set up for another job and we just need a run of 20 boards or such, we will hand-place them.Due to our manufacturing process, I know which boards were hand placed and which were PnP placed, and a proportional quantity of the boards with failed caps were hand placed. I also went through the tub of components that they use when hand placing boards and tested a bunch and found several that were failed with a dead short also.Nothing in the PCB or assembly process has changed - and based on the batch numbers and estimating how many parts are taken off the reel for hand assembly, not only were all the bad parts from a single reel, but it looks like it was just part of the reel that was bad. In other words, it appears that maybe just a couple of meters of that reel had a ton of bad parts and the rest were fine.I wonder if something could have happened during reeling or during storage/transit to cause this? Like the reel got squished by something or someone dropped something on it in the shop?

author: Leo Bodnar
author_rank: Frequent Contributor
timestamp: October 13, 2017, 10:12:49 pm
content: Quote from: Corporate666 on October 13, 2017, 10:09:00 pmDo you use DK re-reeling service or buy full reels?Leo

author: TimNJ
author_rank: Super Contributor
timestamp: October 13, 2017, 10:20:18 pm
content: Ceramic caps, especially those with class 2 dielectrics (X7R), are prone to endcap separation due to mechanical stress. Caps placed near the edge of a board or near heavy components are more likely to fail. Also, an incorrect soldering temperature profile, or even worse, hand soldering, can cause the endcaps and ceramic chip to expand at different rates and crack. NP0/C0G caps don't experience these problems as much.You might want to take a look at MLCCs with "flexible terminations" like FT-CAP from Kemet:http://www.kemet.com/Lists/ApplicationBriefs/Attachments/58/Flexible%20Termination%20Technology%20(FT-CAP).pdfThese caps have a layer of a epoxy (of some sort) that make them more resilient to mechanical stress.

author: Leo Bodnar
author_rank: Frequent Contributor
timestamp: October 13, 2017, 10:24:13 pm
content: I know this is internet but could we please concentrate on the fact that a lot of failed caps have never been on the PCB in their entire life?

author: rx8pilot
author_rank: Super Contributor
timestamp: October 13, 2017, 10:25:57 pm
content: Following this thread.....Sent from my SM-G892A using Tapatalk

author: thm_w
author_rank: Super Contributor
timestamp: October 14, 2017, 12:10:36 am
content: 5% is incredibly high, did you contact Samsung with the production date to see if they can provide any insight?Quote from: Leo Bodnar on October 13, 2017, 09:01:17 pmYes, same experience here, a few ceramics failed after production (<0.1%), and a handful failed returned from the field (<0.2%). Its always the same ones in the power section, so maybe they are stressed or due to their larger size (1210 10uF 25V X7R Murata).In the field case they could have been abused (overvoltage, roughly handled in shipping, etc.), so cannot say for sure if they were actually defective.

author: wraper
author_rank: Unknown
timestamp: October 14, 2017, 08:24:51 am
content: Quote from: thm_w on October 14, 2017, 12:10:36 amIt's not "OR" situation. Larger sizes are more susceptible to mechanical stress. I would look into how caps are mechanically located and how these boards are depanelized. You could, say, rotate them by 90oand this could fix the issue.QuoteIf there is mechanical stress at production, they may fail short later. Overvoltage unlikely to be the issue, MLCC easily survive 10x of the rated voltage.

author: Psi
author_rank: Super Contributor
timestamp: October 14, 2017, 10:43:28 am
content: I've seen some 10uF Yageo 0603 caps fail semi-shorted recently. But being cheap Yaego caps it didn't surprise me that much.

author: SeanB
author_rank: Super Contributor
timestamp: October 14, 2017, 11:18:58 am
content: Position dependant on the reel only, so my guess is that the reel was dropped at some point on edge on a hard surface. Check the reel itself for edge damage, and you will find a flat spot where it deformed. Likely the reel tape inside was not tightly wrapped, and the loose turns had enough shock from hitting each other to crack the capacitors as they impacted inside the reel tubs and crack them.Take the reel, and sacrifice a few meters of capacitors, peeling the tape off after attaching the reel to a hard flat surface, and look inside the plastic tubs to see the indents the capacitors would have left there on impact. Use a microscope to see, and take a photo of dented versus undented, and have a word with the supplier and the shipper, for both dropping shock sensitive items and for not packing properly in a box with adequate shock dampening material.

author: Corporate666
author_rank: Unknown
timestamp: October 15, 2017, 06:28:38 am
content: Quote from: Leo Bodnar on October 13, 2017, 10:12:49 pmBought as a full reel, new in package.

author: Corporate666
author_rank: Unknown
timestamp: October 15, 2017, 06:32:45 am
content: Quote from: thm_w on October 14, 2017, 12:10:36 amI haven't, but I will probably do that this week. I don't imagine much of a result... especially since the reel has since been used up and the only parts I have are the failed ones, those in the hand-placement tub, and the miplaced parts catcher from the PnP. At best they will ask for some of the parts back for analysis and maybe will send me some replacements. We'll see.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: October 15, 2017, 09:01:01 am
content: FWIW, 1210 is large, but even the conservative IPC doesn't worry about them: in fact, they recommend 1210 as the largest reliable size.In any case, forget about soldering defects, parts were bad off the reel. Can't people read?Second the suggestion of calling Samsung and notifying their quality dept somehow. Or if not them directly, then the supplier -- for that matter, I suppose you might ask if you can get a refund/credit or replacement for the bum parts. Then if they decide to notify the mfg, it's up to them (and they probably have better contacts than you, anyway?).Tim

author: Leo Bodnar
author_rank: Frequent Contributor
timestamp: October 16, 2017, 08:35:24 am
content: Quote from: Corporate666 on October 15, 2017, 06:28:38 amCorporate666, I have just received DK order.There is good news and bad news.Good news is there are no shorts.Bad news is capacitance is about half of what you'd expect. They are all in the 13-14µF range.Leohttps://www.digikey.co.uk/products/en?keywords=1276-6780-1-ND1276-6780-1-ND .07430 7.43 T CAP CER 22UF 16V X5R 0805HTSUS: 8532.24.0020 ECCN: EAR99LEAD: LEAD FREE ROHS: ROHSMercury: Cert on File.For more information contact RoHS@DigiKey.comCOUNTRY/ORIGIN:CHINA

author: jbb
author_rank: Super Contributor
timestamp: October 16, 2017, 08:58:35 am
content: Half the expected value is odd, unless it's due to DC bias. Do you know what voltage is applied by your capacitor meter?X5R and similar dielectrics actually loose a lot of capacitance when DC voltage is applied. Some manufacturers are more forthcoming than others about this. There should be a capacitance vs DC bias curve in the data sheet or part technical information to help with your design.

author: Leo Bodnar
author_rank: Frequent Contributor
timestamp: October 16, 2017, 09:06:23 am
content: Quote from: jbb on October 16, 2017, 08:58:35 amI have three meters from various brands and they all show the same value. Don't really have time to look it up but i'd be amazed if there is any DC bias beyond few mV. I trust Agilent not to be complete idiots.Leo

author: BFX
author_rank: Frequent Contributor
timestamp: October 16, 2017, 11:49:09 am
content: @LeoCapacitors >10uF should be measured at 120Hz +-20%.I see on your meter 1kHz. That could be problem.

author: Ice-Tea
author_rank: Super Contributor
timestamp: October 16, 2017, 12:02:37 pm
content: I noticed that you never outright say whether you bought them at DK or not... Did you?Also, I agree: get in touch with Samsung. Failing components off the reel should be in the low ppm region. Or, you know, nothing at all.

author: wraper
author_rank: Unknown
timestamp: October 16, 2017, 12:05:04 pm
content: Quote from: BFX on October 16, 2017, 11:49:09 amThis, also a significant part of capacitance drops because of ageing. Leo, reheat the capacitor with the hot air or soldering iron, let it cool down for some time and measure again.

author: Leo Bodnar
author_rank: Frequent Contributor
timestamp: October 16, 2017, 12:05:33 pm
content: Quote from: BFX on October 16, 2017, 11:49:09 amNot that much different - still 25% down from nominal.Leo

author: wraper
author_rank: Unknown
timestamp: October 16, 2017, 12:07:50 pm
content: Quote from: Leo Bodnar on October 16, 2017, 12:05:33 pmThis is completely normal. Do as I said above and capacitance will be within rated tolerance.

author: Leo Bodnar
author_rank: Frequent Contributor
timestamp: October 16, 2017, 12:57:17 pm
content: After Pb-free reflow cycle it went up to 19.8µF. I'll let it pass.Leo

author: thm_w
author_rank: Super Contributor
timestamp: October 17, 2017, 12:13:26 am
content: Quote from: wraper on October 16, 2017, 12:05:04 pmHad no idea it was this significant (10% after 1000hr on X7R):http://www.johansondielectrics.com/ceramic-capacitor-aging-made-simpleAs you said:QuoteAnother reason to not touch Y5V..

author: Leo Bodnar
author_rank: Frequent Contributor
timestamp: October 17, 2017, 07:34:01 am
content: Quote from: thm_w on October 17, 2017, 12:13:26 amAlso partial reason for why you can seemingly fix some hardware by magically "reflowing" it in kitchen oven.Leo

author: Siwastaja
author_rank: Super Contributor
timestamp: October 17, 2017, 08:16:33 am
content: Quote from: thm_w on October 17, 2017, 12:13:26 amEven X7R can be quite horrible, some "poor" X7Rs are as bad as some other "good" Y5Vs. You always need to check the actual curves of the exact component (if available). Rule of thumb: a smaller ("too-good-to-be-true") device usually has worse DC bias, ageing and temperature characteristics, all at once.So simply avoiding Y5V might not be enough. A lot of homework to do when designing.(Edit: sorry for OT. The issue here is the case of broken components on the reel / taken from the reel, not soldered.)

author: wraper
author_rank: Unknown
timestamp: October 17, 2017, 09:05:17 am
content: Quote from: Leo Bodnar on October 17, 2017, 07:34:01 amIt's not like this actually unless device is poorly designed. When heating shorted/leaky MLCCs, they often start working normally for some time. Therefore trying to find shorted component on the rail with a lot of MLCCs on it may be a big PITA. Say you desolder some MLCC or MOSFET and it becomes fine. And then you don't know which part was actually faulty. Lois Rossmann was talking about this issue on his youtube channel as well, when explaining GPU reflow nonsense performed by con artists or clueless. Particular models of Macbook may have shorted MLCC under GPU and when "reflowed" it starts working again for some time.If I suspect shorted MLCC, I apply voltage to the rail from lab PSU and look with thermal imager as basically this is the only easy way to know for sure that short is in particular MLCC.This could also explain why OP has many returns. Shorted caps might become working when reflowed and pass all tests. And during MLCC production this could happen as well as they are heated several times and then pass the tests.

author: jmelson
author_rank: Super Contributor
timestamp: October 17, 2017, 08:39:53 pm
content: Do you have any of these still on the original tape? I'm wondering if the placement/handling forces on the P&P machine is possibly cracking the parts. If you can find defective parts still in the tape, that would eliminate any handling issues in your facility.Hmmm, 22 uF in an 0805 package? Wow, that's a lot of capacitor in a small body. And, they claim low moisture sensitivity.Jon

author: Corporate666
author_rank: Unknown
timestamp: October 18, 2017, 12:25:09 am
content: Quote from: Ice-Tea on October 16, 2017, 12:02:37 pmYep, I bought them direct from DK, new on the reel.I got in touch with Samsung and after much transferring and people answering the phone who had no idea who I should talk to, I finally got someone who knew what they were talking about.Their answer is that they have never heard of such an issue before, that it must be something I did, but I am welcome to send them any parts in my possession that failed testing and they will replace them like-for-like.So basically totally unhelpful.

author: IDEngineer
author_rank: Super Contributor
timestamp: October 18, 2017, 01:16:11 am
content: Quote from: Siwastaja on October 17, 2017, 08:16:33 amThis. Exactly this. I just handled populating the BOM for a new product and I spent more time on cap selection than any other type of component. There is NO consistency across manufacturers... sometimes Samsung has the better curves in its spec sheet, other times Taido Yuden, sometimes Murata, etc. Yaego doesn't even publish some important curves for many of their caps, so their products don't get approved for our projects.There are no ideal components, but caps are especially weird beasts. We try hard to never run them beyond 33% of their rated voltage (5V bypass caps are always at least 15V, and often 25V) and then we consult the curves to see how they are derated with DC bias. We recently dropped 4.7uF/25V caps in one 12V application because we found that a 10uF/25V we were already using had MORE than 4.7uF effective capacitance at 12V. (Imagine what the 4.7uF looked like at 12V.) Yes, it violates our "33%" rule but if we're making an informed decision, operating within specs, and still below 50% rated voltage, why stock both parts? With the increased volume of the single part the price was basically a wash. The package sizes were the same too.

author: georges80
author_rank: Frequent Contributor
timestamp: October 18, 2017, 02:50:37 am
content: Quote from: Corporate666 on October 18, 2017, 12:25:09 amI wouldn't say unhelpful, but realistic. Pull parts off your reel and send them in for testing if you are positive that the problem was not caused by mishandling in the supply chain or within your own assembly/storage facility.I've sent components to manufacturers and that is the correct way to determine the actual problem versus expecting the internet to resolve the issue... Not being harsh, but consider that they have the equipment to determine if the faults are in handling or in the original Samsung assembly. I've used and use Samsung caps (as well as other mainstream sources) and never seen issues that weren't directly attributed to handling/assembly issues on the assembly floor - even then it is in the percent of a percent (or less)...cheers,george.

author: Corporate666
author_rank: Unknown
timestamp: October 18, 2017, 03:10:52 am
content: Quote from: georges80 on October 18, 2017, 02:50:37 amThey are not offering to test and analyze the reason for failure... they stated that this has never happened before, and therefore must have been something I did, but they would replace any failed caps with equivalent parts if I send them in for exchange.I've had similar "service" from Atmel back in the day. I have also had excellent service from Alpha Omega when I was having issues with a regulator failing abruptly in a specific application.YMMV, I guess.

author: exmadscientist
author_rank: Frequent Contributor
timestamp: October 18, 2017, 04:18:30 am
content: Can't say I'm surprised to hear that it's Samsung who made these parts. I've seen one too many odd things with Samsung components and have since blacklisted their passives. Murata is only a tiny bit more expensive and supplies much better specifications and design support tools. TDK, Taiyo Yuden, and Kemet are also good, but rarely better value than Murata. Yageo C0G parts are decent (C0G being harder to screw up than X5R/X7R) and cheap.I agree that selecting capacitors takes a huge amount of design time. About the only thing that takes longer is choosing a diode, but there are many fewer diodes in a design and so the total time is much less. The advice to stick to 1210s and smaller is well taken; the big ceramics are just too fragile.

author: Siwastaja
author_rank: Super Contributor
timestamp: October 18, 2017, 06:12:47 am
content: Quote from: Corporate666 on October 18, 2017, 03:10:52 amAnd, following this logical principle, it will, by definition, never happen.

author: sean0118
author_rank: Frequent Contributor
timestamp: October 18, 2017, 09:44:40 am
content: Send them into Dave to dissect under his microscope.

author: wraper
author_rank: Unknown
timestamp: October 18, 2017, 10:04:37 am
content: Quote from: sean0118 on October 18, 2017, 09:44:40 amDave does not have tools to cut MLCC in half and I don't recall him having a microscope with enough magnification.

author: IDEngineer
author_rank: Super Contributor
timestamp: October 18, 2017, 11:24:11 pm
content: Quote from: exmadscientist on October 18, 2017, 04:18:30 amPlus, if you need higher capacitance, you're better off using multiple caps in parallel anyway. The unwanted ESR and ESL is thus paralleled, reducing the effect of these unavoidable imperfections.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: October 19, 2017, 04:56:17 am
content: Quote from: IDEngineer on October 18, 2017, 11:24:11 pmNot that you have to worry about ESR with ceramics. ESL is a part length thing, so that's true, but you're probably in need of a better solution if you're that critical on it (i.e., adding ferrite beads and additional filtering stages to meet EMC).Personally, I'm not opposed to 1812s, and of course any larger caps on a leadframe are fine (but they're usually prohibitively expensive).Tim

author: Ice-Tea
author_rank: Super Contributor
timestamp: October 19, 2017, 08:00:11 am
content: Quote from: Corporate666 on October 18, 2017, 12:25:09 amYou pretty much have to find a faulty component *on the reel*, without processing further. If you find one of those, they have no place to hide. But I agree with others: chances that it's a Samsung issue are slim to none..