Phil - 
        What is your cleaning process? If you have been using FTIR to look 
     at the residue make sure that your suspect materials have seen the 
     same temperature excursions as the residue has! Your FTIR fingerprint 
     will be different due to changes in the suspect material because of 
     the temperatures. These changes will give you an FTIR false negative 
     test result on your suspect materials and lead you to no longer 
     suspect the 'suspect" samples. I have seen rosin fluxes look quite 
     different after going through a soldering and cleaning process than 
     just testing the flux out of the bottle unprocessed.
     
     Dave Hillman
     Rockwell CACD
     [log in to unmask]
     


______________________________ Reply Separator _________________________________
Subject: White residue between soldered leads
Author:  [log in to unmask] at ccmgw1
Date:    5/7/96 3:21 PM


     I have a white residue problem that is becoming all to common. The 
     white residue appears between and behind soldered leads on the 
     polyimide substrate.  It does not appear on or inside of 
     soldered-through holes.  On some boards I can find it between all the 
     leads.  On others I see it only between a few leads.
     I have analyzed this residue many times with FTIR.  Everytime, I get 
     proteinaceous matter (protein).  I see no evidence of rosin-based or 
     water-soluble flux, but at times I see cellulose fibers mixed in with 
     the proteinaceous matter.
     
     What is this stuff?
     
     We have considered:
     
     1. skin residue (dandruff)
     2. debris from camel hair brushes
     3. fungus
     
     There appears to be far too much residue to consider 1. and 2. 
     The problem appears after the final cleaning/rinsing step.
     Any ideas would be greatly appreciated.
     
     Thank you.
     
     --Phil