Our standard note for this is:
18. [x] NO THIEVING MAY BE ADDED TO THIS DESIGN, FABRICATOR SHALL
USE ONLY AREAS
OUTSIDE OF THE BOARD EDGE ROUTING TO BALANCE COPPER DENSITY.
[ ] THIEVING MAY BE ADDED IN THE INDICATED AREA TO COMPENSATE
FOR LOWER
DENSITY AREAS IN THIS DESIGN. THIEVING MUST MEET THE
FOLLOWING SPACING
REQUIREMENTS:
A.) NO EXPOSED THIEVING IN AREAS WITH REMOVED SOLDER MASK OR
INTERNAL
COPPER PLANE.
B.) THIEVING SHALL MAINTAIN A MINIMUM CLEARANCE OF 0.100 FROM
ALL
COPPER BOARD FEATURES.
C.) THIEVING SHALL MAINTAIN A MINIMUM CLEARANCE OF 0.250 FROM
ALL BOARD
EDGES, AND FIDUCIALS.
And for the most part the first option is the preference of the
designers, we put a lot of time in to the design of our boards and would
prefer that that they not be changed with out our input.
Jeffrey McGlaughlin, CID
Engineering Designer
Battelle
505 King Avenue
Columbus Ohio 43201-2693
(614)424-7582 Phone
(614)458-7582 Fax
-----Original Message-----
From: DesignerCouncil [mailto:[log in to unmask]] On Behalf Of
Tempea, Ioan
Sent: Friday, February 23, 2007 11:11 AM
To: [log in to unmask]
Subject: [DC] Copper balancing
Dear colleagues,
very often, the PCB layout designers would draw the circuitry and write
a note on the fab drawing asking that the copper be balanced by the PCB
house, by adding non-functional copper.
The question I have is: how does the PCB house know how much copper to
add and where to add it? Are there any scientific bases, some
calculations, or is it based on experience? Otherwise said, if the PCB
house will balance the copper, this means the warpage worries are gone,
or just that there are chances it will warp less?
And to make it tougher: if we leave the latitude of choosing the right
substrate and doing the balancing to the board shop, can they guarantee
stable boards?
Thanks,
Ioan
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