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Fri, 26 Feb 1999 15:15:46 -0600 |
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<5804581625021999/A03237/NPL3/11D2CC393600*@MHS> |
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Hi Bryan,
I'm Curious as to what Class copper you are using on the Inner layers. We have
found that in the past that class-1 copper would not cut it, and switched to
Class-3 Copper which is more ductile. This practically eliminated foil
cracking.
Regards,
Les
> From: Bryan Kerr +44 1383 822131 ext 4409 <[log in to unmask]>, on 2/25/99
> 4:58 PM:
> On this subject, I have recently been investigating an open circuit problem
> with a multilayer board and have found a small, but significant, level of
> foil
> cracking at the hole / inner layer interface with no apparent reason. There
> are
> no unused pads and I had already been pondering whether the lack of these
> "dummy" pads could result in more stress on the inner layer junctions during
> thermal shock - 288 C for 10 seconds. Maybe any weaknesses in the junction
> are
> more likely to result in fracture if there are no dummy pads ?
> Comments, anybody.
>
> Bryan
>
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