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id m0t5xKH-0000H2C; Thu, 19 Oct 95 10:56 CDT |
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Thu, 19 Oct 1995 11:34:05 -0400 |
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| From [log in to unmask] Sat Apr 27 15: |
07:49 1996 |
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Kevin,
Manuafacturers, for years, have asked for the non-functional lands to be
removed. This is to reduce the opportunity of shorts between inner layer
lands and planes. These areas have ben difficult to inspect.
During the IPC small hole round robin test program, it was verified that high
aspect ratio holes failed in the resin rich areas of the board. By removing
the non-functional lands, on inner layers, you actually increased the resin
rich area around that hole. Therefore, the IPC-D-275 recommended not removing
the non-functional lands.
However, high layer count PWB's develop a compression problem, during
lamination, when copper lands are included on all layers. The recommendation
is to take some of the non-functional lands out of the stack, for the high
layer count PWB's.
To remove, or not to remove should be primarily a reliability issue.
Regards,
Gary Ferrari
Tech Circuits
(203)269-3311
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