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March 1998

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Subject:
Re: ASSY: Intermittent Short
From:
"SEM Lab, Inc." <[log in to unmask]>
Reply To:
[log in to unmask]
Date:
Wed, 11 Mar 1998 12:22:08 -0600
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text/plain (54 lines) 
Christy,

For what its worth ...

I've seen intermittent internal shorts in printed wiring boards that were later found to be
caused by etch defects that had left copper in a ground plane clearance zone around a via.  The
copper was nearly touching the via land but not quite, and when the board warmed up there was
enough movement to cause the board to short.

Ed Hare
SEM Lab, Inc.
--

               SEM Lab, Inc.
Scanning Electron Microscopy and Failure Analysis
               Snohomish, WA
               (425)335-4400
   http://www.eskimo.com/~eriemer/SEMLab.htm

Christy Graham wrote:

> TechNet,
>
> I was told recently of a printed circuit card assembly that, when the
> assembly is powered up in the morning, the board runs, but that by the
> afternoon, it fails.  Next day, same board, same results.  The engineer
> thinks this problem is due to a "flux short".  Is this possible?
>
> Christy Graham
> [log in to unmask]
>
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