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