Paresh,
          
          It might be that you have voids in the PTHs of your PWBs 
          which are outgassing as trapped moisture vaporizes when your 
          parts.  This outgassing forms a solder bubble which pops out 
          of the hole and looks like a large solder ball.
          
          I've seen quite a bit of this myself lately.
          
          Dave Sullivan


______________________________ Reply Separator _________________________________
Subject: Solder Balls
Author:  [log in to unmask] at ccmgw1
Date:    6/30/97 10:28 AM


     Good morning everyone,
     Lately, we are experiencing solder balls on the top side of single 
     side PWB.  There are some holes that do not get any components before 
     wave solder.  When the board hits wave, it makes "frying" noise and 
     next thing you see is solder balls.  There are two bottom pre-heaters 
     set at 450 F & 475 F.  Solder temp is 500 F.  Conveyor speed is  6 
     fpm.
          
     This problem occurred in the past and was solved by increasing 
     pre-heat temps.  which were originally 325 F & 350 F.  Now we are at 
     the peak of  highest component heat ratings.  I checked several boards 
     and made sure that there is no flux left on the bottom side before it 
     hits solder wave. 
          
     Any suggestion on what should I try next will help.
          
     Thanks in advance,
     Paresh Patel
     Oneac Corp.
     (847)816-6000 X-704
          
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