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Thu, 13 Sep 2007 14:57:57 -0400 |
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On 2007-09-13 12:58, John Burke wrote:
> I am assuming that the close up shots are Z axis sections?
Yes. Sorry, I should have described them better.
> Which if they are, and those are indeed inner layers, the
> board is showing signs of unusual localized deformation since
> the "two halves" of the break are not aligned, and if this is
> indeed an inner layer section, they should be, broken or not.
Yes, I believe there are two phases leading to the final
condition: an inital defect (still very conductive), followed
by later separation (higher R or open), possibly under stress.
> Have you taken a look at the test fixture for the final board
> assembly? You can sometimes get very bad local board
> deformation due to uneven pusher pin distribution.
No but that is an interesting suggestion, thanks.
Mike
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