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Date: | Fri, 14 Jul 95 09:07:57 CST |
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For electrical considerations, some designers will use an automatic
fill command to put ground plane in "open" areas of their boards.
This will, in most cases, also help out in current distribution during
plating. But there is no such thing as a free lunch. We are having
some (OK a lot of) discussion concerning the best fill geometry to
use. The two main contenders are solid and cross hatching on 15 mil
centers. My "opinion" concerning the two methods:
Crosshatching
Advantages; less Gerber data, better adhesion to FR-4 than bare
copper, cosmetically more appealing, less thermal mass for soldering
process
Disadvantages; (a major one) Slivers,places where photoresist
can lift and redeposit [Our design system does not automatically
prevent formation of these slivers prior to producing a Gerber file],
hard to visually inspect
Solid fill
Advantages; No slivers, easier to inspect
Disadvantages; More gerber data, more thermal mass for soldering
processes, greater chance for discoloration of bare copper under
solder mask, less adhesion
Our main concern is with the slivers associated with crosshatching.
Does anyone have suggestions concerning area sizes that should be
crosshatched? Is there a better geometry to use? What are you doing
to prevent slivers in your designs?
Regards,
Jamie Baumgart
DSC Communications
(214) 519-2500
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