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Current spiking X7R

Current spiking X7R

Current spiking X7R

(OP)
I'm attempting to degrade a 0.22 uF MLCC (X7R dielectric) through current spiking.  What magnitude spike do I need to be slamming into this device in order to start causing damage? (even a rough order of magnitude would be helpful)

Spec sheets aren't getting me anywhere (I get a 500v rating, but no current information), and google isn't being very helpful.  If anyone has either advice, or resources regarding this problem, it would be greatly appreciated.

Thanks,
HRearden

RE: Current spiking X7R

(OP)
While I'm sure that a 10kV, 1 MA spike would be enough to inflict damage, I'm trying to do this in a controlled manner.

"degrade", not "vaporize"... thumbsup

RE: Current spiking X7R

Well those appear to be rated for DC service.
Feed one AC.
Feed one with 10% over its voltage rating.

Be helpful if you explained a bunch more. Part of Dan's facetious answer was due to the lack of any useful aspect to your test request.

Typically someone out to thrash components is doing it to prove the component is going to be robust enough for its task.  The task being the environment and its connection to that environment.

A test should be comprised of taken-to-the-limit conditions expected in service.

Why are you testing this cap?

Keith Cress
Flamin Systems, Inc.- http://www.flaminsystems.com

RE: Current spiking X7R

The rule with pulse currents is "consult factory."  A good manufacturer should be able to give advice on reliaility and limits of pulsed currents.  One thing I remember about ceramics is that the ceramic is a little piezoelectric meaning they change shape when pulsed creating mechanical stresses.

RE: Current spiking X7R

(OP)
"Typically someone out to thrash components is doing it to prove the component is going to be robust enough for its task.  The task being the environment and its connection to that environment.

A test should be comprised of taken-to-the-limit conditions expected in service.

Why are you testing this cap?"

The focus really isn't on the cap; the cap happens to be part of the input filter to a power supply.  My goal is to degrade the supply (on the component level)-in particular an input filter fault, and see if we can detect faults/failures as part of a diagnostic effort.  Thus, I have a need for capacitors that are actually degraded, so that we can insert them into the supply to create the necessary fault condition.

Sreid: I have contacted the factory, but I've yet to receive any information back from them.

RE: Current spiking X7R

"Degrade?"

In a "controlled" manner?

I think that you will have to rethink here.

Do you want to test the test rig/people to see if they can catch a faulty capacitor?

Wouldn't it be easier to arrange the fault outside the capacitor. In a controlled manner. Like using a resistor for leakage. A spark gap (one of those gas voltage arresters) for possible punch-through. A capacitor with wrong value for tolerance check. Or even a flakey connection for internal weld faults?

Having all these separate faults from a zap is probably not possible.

Gunnar Englund
www.gke.org
--------------------------------------
100 % recycled posting: Electrons, ideas, finger-tips have been used over and over again...

RE: Current spiking X7R

(OP)
We have had success with controlled degradation of other components (both mechanical and electrical) in the past.  The reason I pose the question is the lack of technical information that I've been able to locate regarding the properties of the dielectric and potential current tolerance.

"Do you want to test the test rig/people to see if they can catch a faulty capacitor?"  That's more or less the idea.  We have algorithms in place to characterize these systems, and we want to be able to create a system that can achieve that automatically.  As I said in the previous paragraph, the use of truly faulty materials has been successful in the past in similar efforts.

I just got an email back from AMC - they have no idea what the caps will tolerate.  I guess it's "recon by fire" time...

Thanks for the input.

RE: Current spiking X7R

OK Hank. I am interested in the result.

Gunnar Englund
www.gke.org
--------------------------------------
100 % recycled posting: Electrons, ideas, finger-tips have been used over and over again...

RE: Current spiking X7R

Yes I am too.

  I also agree with Skogs in that the best solution is to simulate the possible failures.

  You will never, ever, achieve the full range of possible results from the technique you are embarking on.

Keith Cress
Flamin Systems, Inc.- http://www.flaminsystems.com

RE: Current spiking X7R

Keith,

I insist on you or someone else asking why I named him Hank (I feel soo smart)

Gunnar Englund
www.gke.org
--------------------------------------
100 % recycled posting: Electrons, ideas, finger-tips have been used over and over again...

RE: Current spiking X7R

Why did you name him Hank???
I thought 'H' stood for Harlequin. <just kidding>
I actually thought you were just being jocular.  Like saying, "Okay Buddy".

Keith Cress
Flamin Systems, Inc.- http://www.flaminsystems.com

RE: Current spiking X7R

I thought you'd never ask!

I did read the "Atlas shrugged" by Ann Raynd. There is a guy named Hank Rearden. (And also John Galt, which is my alter ego in some Swedish fora).

There. Simple!

I am soo glad you asked.

BTW. I had a couple of beers with friends. German guys. So I am a bit more relaxed than usually.

Gunnar Englund
www.gke.org
--------------------------------------
100 % recycled posting: Electrons, ideas, finger-tips have been used over and over again...

RE: Current spiking X7R

Sorry, read Ayn Rand. The beers, probably...

Gunnar Englund
www.gke.org
--------------------------------------
100 % recycled posting: Electrons, ideas, finger-tips have been used over and over again...

RE: Current spiking X7R

Go to AVX

http://www.avxcorp.com/

And click Spice Models/ Software

SPICAP should give you msximum ripple current vs. frequency and temperature.

RE: Current spiking X7R

Even as an electrical engineer, I think I enjoyed The Fountainhead more than Atlas Shrugged (though both were great books).  Ayn tends to be pretty long-winded in her descriptions, particularly of buildings in The Fountainhead, so I admit I occasionally skipped a few pages when she turned into a windbag.  Still, I finished it in a day and a half.

Dan - Owner
http://www.Hi-TecDesigns.com

RE: Current spiking X7R

Those numbers are for design. Going higher does not mean that you change the capacitor instantly. Not 50 % higher, probably not even 100 %. What happens is that a certain percentage of a batch will have a reduced life. Perhaps 10 kh instead of 100 kh - or something.

The problem is that any change will take a very long time and that you probably do not get a "nice degradation" but rather a complete failure.

Gunnar Englund
www.gke.org
--------------------------------------
100 % recycled posting: Electrons, ideas, finger-tips have been used over and over again...

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