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Thu, 25 Sep 2003 18:40:24 -0400 |
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Applied CAD Knowledge, Inc. |
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"Miswald, Ron" wrote:
>
> Our board house is raising a flag about our IPC-356 netlists. Their concern
> is that we short various grounds due to short comings in out layout
> software. As an example we have digital ground, 1.8V crystal ground, and
> 3.3V crystal ground segregated until they tie together (short) at the power
> supply.
This problem is inherent in most folks' design methods.
Once you get to fab, there can be no such thing as an
intentional short. These things cause phone calls, or
worse. For this reason we had to cook up a way to bridge
the engineer's intent with the reality of the CAD system.
Admittedly a proprietary solution, we can map these items
to understand the engineering need and produce correct
reference files for fabrication.
>
> My question, are there easy work arounds for the board house? I do include
> a readme listing the ties, the nets they short, and their (x,y) locations.
>
One possible quick solution is to record a macro in your
editor of choice to combine the nets in your output IPC
netlist file. This is what you're asking the fab vendor
to do but if I were they I'd be really really nervous
about it - too nervous to be responsible in fact - as it
stands they lack sufficient reference to prove they've
done it correctly.
In fact I wouldn't recommend this solution unless your
process allows for final CAE/CAD comparison as well as an
in-house Gerber to IPC compare.
Good luck with this thorny issue, but props on trying to
use the IPC netlist correctly. It's tough but invaluable
in my experience.
--
Jeff Seeger Applied CAD Knowledge Inc
Chief Technical Officer Tyngsboro, MA 01879
jseeger "at" appliedcad "dot" com 978 649 9800
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