Why via plug on the component side? This allows solder to wick up into 
     the hole and it's looking for someplace to go. Try via plugging on the 
     "solder" wave side of the board which will prevent solder from wicking 
     into the hole. As to industry standards, my experience has been to 
     plug in this manner. Very few (count `em on one hand) customers of 
     mine have requested plugging on the top side.
     
     Regards,
     
     Tom Bresnan
     


______________________________ Reply Separator _________________________________
Subject: Re: Assembly - via hole plugging and solderballs
Author:  [log in to unmask] at INTERNET_GATEWAY
Date:    4/2/97 4:24 P


Item Subject: Assembly - via hole plugging and solderballs
     What you are seeing is the outgassing of the flux through the wave 
     soldering process.  This is a very common problem and the best method 
     is to not mix mixed technology boards with plugged vias.  I have never 
     heard of any solution to this when wave soldering is involved.
     
     
______________________________ Reply Separator _________________________________
Subject: Assembly - via hole plugging and solderballs
Author:  Non-HP-Marti.tully ([log in to unmask]) at 
HP-Vancouver,shargw2
Date:    4/2/97 2:29 PM
     
     
Several of our PWB suppliers have used a via hole plugging process with the 
following sequence:  LPI, HASL, partially plug via hole (component side). 
   With mixed technology boards, our assemblers (in house, contracted etc.) 
all experience a phenomenon where the solder erupts from the top of the via 
during the wave process.  The eruption looks like a volcano and varies in 
severity.  This eruption  results in several problems including solderballs. 
  Most of the plugged vias lie under components and the spacing between vias 
can be equal to or <8mils.  Many components sit very close to the board's 
surface.
     
This seems the  PWB industry preferred method to plug holes when LPI is 
used.    How do assemblers prevent the eruption of the solder through the 
top of the plugged via during wave?  Is this a common problem in assembly 
 or rare?  
     
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