Do the via plug after Hot Air Solder Leveling.  That should eliminate 
     the problem.


______________________________ Reply Separator _________________________________
Subject: Solder balls
Author:  [log in to unmask] at corp
Date:    5/21/97 12:34 PM


We're having problems with "solder balls" that are "resting in a nest". We 
have .025" via holes that are covered with L.P.I. soldermask. The mask is 
collapsing when going through our vertical hot air leveler and little 
"solder balls" are sitting just inside the holes. The solder balls are 
falling out at subsequent operations and in some cases are ending up between 
contact fingers that have .006" spacing between. The solder balls are 
creating a short at electrical test. They are easily removed but not easily 
detected before hand. Any ideas on what we can do to eliminate this problem?
     
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