HI,
         YOU HAVE NOT STATED WETHER THIS IS A SMT OR THROUGH HOLE 
     COMPONENT, PRIMARY OR SECONDARY SIDE OR THE SOLDERMASK THICKNESS.  
     THAT HAVING BEEN SAID A GOOD RULE OF THUMB WE'VE BEEN USING FOR YEARS 
     IS NO LESS THAN .025'.  THIS ALLOWS FOR A .005" ANNULAR SOLDER MASK 
     CLEARANCE AROUND THE PAD LEAVING .015" SOLDER MASK  DAM BETWEEN PADS.
     DEPENDING ON THE TYPE AND THICKNESS OF YOUR SOLDER MASK YOU CAN GO 
     SMALLER. SOME TIMES GOING SMALLER CAUSES THE SOLDER MASK TO DRAW AWAY 
     FROM ITS SELF, LEAVING A DASHED PATTERN OF SOLDER MASK BETWEEN THE 
     PADS.  THERE IS AN IPC SPEC ON SOLDER MASKS OUT THERE, BUT I DON'T 
     HAVE IT READY TO HAND.  GARY, CAN YOU HELP OUT HERE?
     
     REGARDS,
     
     ROB BUTTERWORTH
     SR PWB DESIGNER
     ADC VIDEO SYSTEMS
     999 RESEARCH PARKWAY
     MERIDEN, CT. 06455
     [log in to unmask]


______________________________ Reply Separator _________________________________
Subject: FAB:ASSY:pad spacing
Author:  [log in to unmask] at internet-mail
Date:    4/18/96 10:26 PM


     
     Typically, what is the minimum spacing between printed circuit solder 
     pads that would allow for enough LPI soldermask to prevent bridging 
     for a wave soldering process ?
     
     Is there a design guideline that specifically addresses this ? If so, 
     can you point me in the right direction.
     
     Any assistance would be greatly appreciated.
     
     Thanks