Rudy,
     Because it was confined to the fine pitch areas, there may be a 
connection to residues but if the problem was solder mask residues, wouldn't 
the result be "non-wetting" with some visible areas of exposed copper?
     These boards were HASL'd by the supplier and they looked just fine. 
 After they went through our IR process, some of the fine pitch pads do not 
stay fully wet with solder.  No exposed copper can be seen, but on some of 
the finished solder connections ~20 - 30% of the pad surface refuses to 
allow the new solder to flow onto it.  Generally these areas are from the 
outside of the pads inward.  None were in the middle of the pad.
      At this point, I'm open to suggestions.

           Norm Dill
           [log in to unmask]
 ----------
From: TechNet-request
To: TechNet
Subject: Re: ASSY: Fine Pitch Dewetting?
Date: Thursday, April 25, 1996 11:19AM

Is it possible that the problem is coming from soldermask residues that the
developer did not remove??  This would account for it not occuring in large
pad areas, as the developer may have trouble getting into the very small
areas.

Rudy Sedlak
RD Chemical

 ----------------------------- Original Post --------------------
     Recently we have seen dewetting (~20 to 30%) that appears only on some
of the fine pitch pads.  Larger pads with various components on the same
boards are ok.  This has been seen on HASL boards from two different
suppliers.  There have been no reports of problems with our regular daily
production lots.
     Any opinions would be welcomed.