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Author Topic: Faulty name-brand ceramic capacitors - common?  (Read 1697 times)

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Online wraper

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Re: Faulty name-brand ceramic capacitors - common?
« Reply #25 on: October 16, 2017, 11:05:04 PM »
@Leo
Capacitors >10uF should be measured at 120Hz +-20%.
I see on your meter 1kHz. That could be problem.
This, 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.
 

Offline Leo Bodnar

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Re: Faulty name-brand ceramic capacitors - common?
« Reply #26 on: October 16, 2017, 11:05:33 PM »
@Leo
Capacitors >10uF should be measured at 120Hz +-20%.
I see on your meter 1kHz. That could be problem.
Not that much different - still 25% down from nominal.

Leo


Online wraper

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Re: Faulty name-brand ceramic capacitors - common?
« Reply #27 on: October 16, 2017, 11:07:50 PM »
Not that much different - still 25% down from nominal.

Leo
This is completely normal. Do as I said above and capacitance will be within rated tolerance.
 

Offline Leo Bodnar

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Re: Faulty name-brand ceramic capacitors - common?
« Reply #28 on: October 16, 2017, 11:57:17 PM »
After Pb-free reflow cycle it went up to 19.8µF.  I'll let it pass.
Leo
 
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Offline thm_w

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Re: Faulty name-brand ceramic capacitors - common?
« Reply #29 on: October 17, 2017, 11:13:26 AM »
This, 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.

Had no idea it was this significant (10% after 1000hr on X7R): http://www.johansondielectrics.com/ceramic-capacitor-aging-made-simple

As you said:
Quote
After the soldering process the capacitors have essentially been De-Aged. Capacitance measurements may be erratic in the initial 10 hours after testing. This is due to the initial capacitance value, dielectric type and the time between reflow and the capacitance measurement. For this reason it may be necessary to wait for the capacitance to stabilize after reflow before testing. In “High K” dielectrics the capacitance may also appear slightly high after the soldering process. This is normal as the capacitance is intended to be stable after 1000 hours so that there is adequate capacitance throughout the life of the circuit

Another reason to not touch Y5V..
 

Offline Leo Bodnar

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Re: Faulty name-brand ceramic capacitors - common?
« Reply #30 on: October 17, 2017, 06:34:01 PM »
Another reason to not touch Y5V..
Also partial reason for why you can seemingly fix some hardware by magically "reflowing" it in kitchen oven.
Leo

Offline Siwastaja

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Re: Faulty name-brand ceramic capacitors - common?
« Reply #31 on: October 17, 2017, 07:16:33 PM »
Another reason to not touch Y5V..

Even 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.)
 

Online wraper

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Re: Faulty name-brand ceramic capacitors - common?
« Reply #32 on: October 17, 2017, 08:05:17 PM »
Another reason to not touch Y5V..
Also partial reason for why you can seemingly fix some hardware by magically "reflowing" it in kitchen oven.
Leo
It'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.
« Last Edit: October 17, 2017, 09:12:56 PM by wraper »
 

Offline jmelson

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Re: Faulty name-brand ceramic capacitors - common?
« Reply #33 on: October 18, 2017, 07:39:53 AM »
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
 

Offline Corporate666

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Re: Faulty name-brand ceramic capacitors - common?
« Reply #34 on: October 18, 2017, 11:25:09 AM »
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.

Yep, 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.
It's not always the most popular person who gets the job done.
 

Offline IDEngineer

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Re: Faulty name-brand ceramic capacitors - common?
« Reply #35 on: October 18, 2017, 12:16:11 PM »
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.

This. 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.
« Last Edit: October 18, 2017, 12:19:26 PM by IDEngineer »
 

Offline georges80

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Re: Faulty name-brand ceramic capacitors - common?
« Reply #36 on: October 18, 2017, 01:50:37 PM »
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.

Yep, 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.

I 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.
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Offline Corporate666

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Re: Faulty name-brand ceramic capacitors - common?
« Reply #37 on: October 18, 2017, 02:10:52 PM »
I 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.

They 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.

It's not always the most popular person who gets the job done.
 

Offline exmadscientist

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Re: Faulty name-brand ceramic capacitors - common?
« Reply #38 on: October 18, 2017, 03:18:30 PM »
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.
 

Offline Siwastaja

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Re: Faulty name-brand ceramic capacitors - common?
« Reply #39 on: October 18, 2017, 05:12:47 PM »
they stated that this has never happened before

And, following this logical principle, it will, by definition, never happen :).
 

Offline sean0118

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Re: Faulty name-brand ceramic capacitors - common?
« Reply #40 on: October 18, 2017, 08:44:40 PM »
Send them into Dave to dissect under his microscope.  ;)
 

Online wraper

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Re: Faulty name-brand ceramic capacitors - common?
« Reply #41 on: October 18, 2017, 09:04:37 PM »
Send them into Dave to dissect under his microscope.  ;)
Dave does not have tools to cut MLCC in half and I don't recall him having a microscope with enough magnification.
 

Offline IDEngineer

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Re: Faulty name-brand ceramic capacitors - common?
« Reply #42 on: October 19, 2017, 10:24:11 AM »
The advice to stick to 1210s and smaller is well taken; the big ceramics are just too fragile.
Plus, 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.
 

Offline T3sl4co1l

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Re: Faulty name-brand ceramic capacitors - common?
« Reply #43 on: October 19, 2017, 03:56:17 PM »
The advice to stick to 1210s and smaller is well taken; the big ceramics are just too fragile.
Plus, 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.

Not 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
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Online Ice-Tea

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Re: Faulty name-brand ceramic capacitors - common?
« Reply #44 on: October 19, 2017, 07:00:11 PM »
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.

Yep, 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.

You 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..
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