I am trying to figure out what the minimum clearance would need to be
between a PCB and a housing that it fits into.  The piece I am not sure
on is the tolerance of the routed edge of the PCB.  The PCB is about
.050 thick and the outline is quite complex with curved edges and
cutouts.  What is the maximum variation in the routed edge that I can
expect from the typical mid-high volume board fabricator?  I have been
told +/-.005 hole to edge and +/-.005 edge to edge.  But what is the
yield at this tolerance?  It is just for straight line routs?  The board
is 4 layers and cost sensitive, so we don't want to over specify the
edge dimension tolerance and drive up cost or limit ourselves to select
few board shops.  
 
I have also seen quotes from Asian sources recommend punching instead of
routing.  Where is a good source of layout design guidelines for this
process? Does it yield good results? I have some knowledge of
singualtion punching, but not in the board fabrication process. 
 
Jim Verrette
Electrical Engineer
 

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