Eric,
 
   I have been putting vias at .014 min to SMT pads for 2 years.  
 QC hasn't had any problems or issues with it.  This is typical 
 for all types of SMT parts.  We choose .014 because it works out 
 well with our pad sizes and a .005 grid.  We used .015 for 3 
 years prior to going to .014.
   The other consideration is your soldermask clearance pad 
 sizes.  You don't want to end up with a soldermask web that is 
 to small or you will get flaking.
 
 
 Brandon Luther
 Dataram Corp.


______________________________ Reply Separator _________________________________
Subject: Via to Smt Pads
Author:  [log in to unmask] at Internet
Date:    3/7/97 10:17 AM


To all PCB Design Conqueror's,
 
  I have a situation arising in our manufacturing facility. We are finally
graduating
to bottom side SMT design. I am butting heads with the IE (Industrial Eng.) 
Dept. on
how close we can place via's to bottom side pads for caps and resistor's. 
Currently
we have a horizontal flow with vertical placement of parts running through the 
wave.
  I started routing boards with a clearance of .015" in any given direction from
the
bottom side pads. My IE Dept. wants a minimum of .025" in any direction, without
having
any source to base this on. Does anyone have a standard that they use or is 
there a 
spec that states how far from a bottom side pad a via should be? 
 
   Thanks.
 
Eric Lucik
[log in to unmask]
 
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