> From:          Davis Ben <[log in to unmask]>
> Subject:       [DC] Solid vs. Hatch
>
> Perhaps my "rule of thumb" is no longer valid or
> was a myth originally.  It is easy convince others about the sucking up
> solder when uncoated issue, but since we have SMOBC they don't see this
> as a problem.  Are the warping and heat sinking issues valid?  Are there
> other issues/concerns I should address or use in my defense?


This is what's in IPC-2222.  Hope this helps.

"10.3 Large conductive areas.  Large vconductive areas
(Planes 3mm wide or larger conductors) increase the likelihood of
blistering, warping or heat shielding during wave or reflow
soldering.

Large areas that cover more than 25.0mm diameter may be
broken up into a cross-hatched or similarly patterned area.
Modifications to large conductive areas shall not adversely impact
the electrical chracteristics or performance of the board. Large
conductive areas should not be on the solder side of the board unless
solder resist or similar is used.

External conductors that extend beyond a 25.0mm diameter circle
should contain etched areas that break up the large conductive area,
but retain the continuity and functionality of the conductor. If
etched areas are not provided, other methods should be used to
minimize blistering or bowing.

Large conductive areas should, if possible, be on the primary side of
the board. If solder resist is employed over meltable metals,
conductive areas wider than 1.3mm SHALL not be employed under the
solder resist coatings.

When a conductive area that extends beyond a 25.0mm diameter is used
on an internal layer, the conductive area should be placed as near to
the center of the board as possible, and contain etched areas that
will break up the large conductive area, but will retain the
continuity and functionality of the conductor. When UL requirements
are imposed, the area SHALL be within the limits approved by UL for
the printed board manufacturer."

JoAnn L. Amerson
Design Librarian
Red Lion Controls, Inc.
E-mail: [log in to unmask]
Voice: (717) 767-6961 ext 6308

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