SOunds like a residue removal problem and the yellowy white colour indicates rosin. You can verify if it is rosin by warming it to say 80-90C - use hot air or a hot plate . If it is rosin then it will melt and become transparent and therefore practically invisible. It will still be there of course, just not so easy to see. If it resin then check your cleaning process, this sort of thing was very common with solvent cleaning so may be you are on HCFC/alcohol and need to improve your process control. If you are using alcohol it may not be possible to eliminate this problem. Alternatively/additionally look at a different paste. All RMA pastes are based on Rosin but solder pastes have other things in the mix as well and some products will clean off more completely/easily than others. If it doesn't melt then you have an unidentified residue which is most likely not relatively benign resin. This being the case I would suggest assigning a higher priority to action. Hope this helps Mike Fenner BSP --------------------------------------------------------------------------------- ------------------------------ Ed Knowles wrote We are noticing a film on our SMT solder joints. It doesn't seem to affect ionic cleanliness or conformal coating adherence, but can only be removed mechanically with a brush or Q-tip. It has a slightly yellowish color in most cases and appears powdery. Is this contamination from the PWB pads or part leads floating to the top, or a compound derived from the solder paste (63/37 RMA)? Any insight into what this contamination is would be appreciated. Thanks. Ed Knowles Lockheed Martin Astronautics *************************************************************************** * TechNet mail list is provided as a service by IPC using SmartList v3.05 * *************************************************************************** * To unsubscribe from this list at any time, send a message to: * * [log in to unmask] with <subject: unsubscribe> and no text. * ***************************************************************************