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July 2008

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Subject:
From:
Guy Ramsey <[log in to unmask]>
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Date:
Mon, 14 Jul 2008 09:59:27 -0400
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I have, over the years, seen both.
In one case the cracked from top to bottom (through the dielectric plates)
was caused by poor machine maintenance. 
Cracks along the plates from end to end was caused by thermal stress. I've
seen this twice actually once cause by too rapid cooling at the reflow exit
and another time induced by a mismatch between an epoxy and an over coat. 
I cannot recall what caused the assembly house to mix the two materials but
the difference in CTE cracked capacitors along the plane of the board, where
the two materials met. These were large capacitors by today's standards,
0805 or 1206.

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Igoshev, Vladimir
Sent: Monday, July 14, 2008 9:08 AM
To: [log in to unmask]
Subject: [TN] Ceramic caps

Hi TechNeters,

I came across an unusual (at least to me) failure mode of ceramic caps.
They crack along the component body in either normal (from top all the way
through to the bottom), or parallel (from one side all the way through to
the other side) direction to the board the caps are mounted on.

Has anyone seen something similar?

Thanks a lot in advance.

Regards,

Vladimir

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