We look for a 3:1 ratio (width:height) - and this all depends on design
and density.

Jeffrey Bush
Director, Quality Assurance and Technical Support
VERMONT CIRCUITS INCORPORATED 
           76 Technology Drive - POB 1890 
              Brattleboro, Vermont 05302
                Voice - 802.257.4571 ext 21
                    Fax - 802.257.0011
                       <http://www.vtcircuits.com/> 
                           

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Phil Nutting
Sent: Thursday, September 28, 2006 12:21 PM
To: [log in to unmask]
Subject: [TN] copper weight versus SMT component size

Has anybody defined recommended maximum copper thickness (weight) with
specific size SMT components?
 
For example; 2 oz. copper max with 0603 resistors and caps.
 
My thoughts process here is I know that with thicker copper there is
more undercut by the etchant.  There must be a point of diminishing
returns for pad size to maintain good manufacturing capabilities, not to
mention the remote possibility of rework.
 
Some of our "power electronics" boards may be specified as 4 oz. copper
for the large power components, but this might be an issue for the small
control circuit components like 0603 foot prints.
 
Thanks in advance.
 
Phil Nutting

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