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July 2008

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Subject:
From:
"Igoshev, Vladimir" <[log in to unmask]>
Reply To:
TechNet E-Mail Forum <[log in to unmask]>, Igoshev, Vladimir
Date:
Mon, 14 Jul 2008 16:04:23 -0400
Content-Type:
text/plain
Parts/Attachments:
text/plain (186 lines)
I don't know. They reportedly showed a short and it happened during a
test (the boards had been functional for quite a few hours and then
failed). I was assured (or should I say told) that the board temperature
should have been holding steady.

Regards,

Vladimir

-----Original Message-----
From: Guy Ramsey [mailto:[log in to unmask]]
Sent: Monday, July 14, 2008 4:00 PM
To: 'TechNet E-Mail Forum'; Igoshev, Vladimir
Subject: RE: [TN] Ceramic caps

If you energize them, do they get hot or do they then open up?
My experience with caps that fractured from end to end, the length of
the
plates, the parts opened up. It was caused by a shearing force as two
different materials expanded at different rates. I don't see how they
would
short.

Once when I was auditing a facility I heard the sound of boards sliding
into
each other. They had built a little ramp off the reflow oven so the
parts
could slide down onto a table to cool. Things piled up at the end while
the
operator was engaged in other activities. Little SIMMs, in six up
panels, in
this case the caps were sheared off the board.

Needless to say they had some explaining to do.



-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Igoshev, Vladimir
Sent: Monday, July 14, 2008 3:05 PM
To: [log in to unmask]
Subject: Re: [TN] Ceramic caps

Yes. They are all identical and they all show a short, which doesn't
make
much sense to me. That is why I keep thinking it's a manufacturing
defect.

Regards,

Vladimir

-----Original Message-----
From: Stadem, Richard D. [mailto:[log in to unmask]]
Sent: Monday, July 14, 2008 3:01 PM
To: Igoshev, Vladimir; TechNet E-Mail Forum
Subject: RE: [TN] Ceramic caps

Totally understand.
The MLCCCs are in a sort of laminated configuration, with the capacitive
plates stacked on top of dialectrics. They vary depending on the value,
ie,
the higher the capacitance, the more layers and the thinner/thicker the
dielectric in between each one. As a result, I know that higher values
of
capacitance have more of a tendency to fracture with a lateral
delamination
than smaller capacitance values do (I think I said that correctly). Are
the
caps that are fracturing all of the same value?

-----Original Message-----
From: Igoshev, Vladimir [mailto:[log in to unmask]]
Sent: Monday, July 14, 2008 1:55 PM
To: TechNet E-Mail Forum; Stadem, Richard D.
Subject: RE: [TN] Ceramic caps

I know Steve would do it, but I need a permission form the "local
authorities" so to say :-)

Regards,

Vladimir

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Stadem, Richard D.
Sent: Monday, July 14, 2008 2:49 PM
To: [log in to unmask]
Subject: Re: [TN] Ceramic caps

Vladimer, if you have photos you can email them to Steve Gregory. Steve
is a
gentleman and a scholar of the industry who posts photos so all of us
can
see, then it is easier to make a "root cause" analysis or just a WAG.
Steve's email address is [log in to unmask]

-----Original Message-----
From: John Maxwell [mailto:[log in to unmask]]
Sent: Monday, July 14, 2008 1:44 PM
To: TechNet E-Mail Forum; Stadem, Richard D.
Subject: Re: [TN] Ceramic caps

Richard & Vladimir,
It would be helpful to post the photos and then I can comment.

John Maxwell
> Vladimir
> Here are potential causes of MLCCC cracking, and how to tell what
> caused the crack based on the crack's position, run direction, etc.
> http://www.ami.ac.uk/courses/topics/0179_fmcc/index.html#3
>
> http://www.syfer.com/category_docs/AN0005_Mechanical_Cracking.pdf
>
> And an authorative paper on the subject by John Maxwell, who I think
> knows more about root causes of cap cracking than anyone:
>
> http://www.avx.co.il/docs/techinfo/cracks.pdf
>
> And a potential solution to the problem:
>
> http://www.avx.co.il/docs/techinfo/mlccflex.pdf
>
> Qualify it first.
>
> -----Original Message-----
> From: TechNet [mailto:[log in to unmask]] On Behalf Of Igoshev, Vladimir
> Sent: Monday, July 14, 2008 1:13 PM
> To: [log in to unmask]
> Subject: Re: [TN] Ceramic caps
>
> Well, in the case I was asking about none of the failures were in that

> direction (across the body) but always along it splitting both ends in

> half either vertically or horizontally. Still a puzzle to me :-)
>
> Regards,
>
> Vladimir
>

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