Hi Paul - I suggest you run a Scanning Electron Microscopy (SEM-EDS)
and/or Fourier Transform Infrared (FTIR) analysis of the red-brown rust
like residue. The number of times I have run into Pb oxide it has been
dark-to-light gray in appearance. The rust like residue could be flux,
something in your wash system, copper oxidation, your wash system reacting
with another area on the assembly and depositing around the solder joints,
etc. Visual appearances can be very misleading - get some analysis data to
save time/cost on developing a solution eliminate the residue. Good Luck.

Dave Hillman
Rockwell Collins
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Paul Wareham <[log in to unmask]> on 01/15/99 03:00:29 PM

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Subject:  [TN] Orange Rust around solder joints




We've just finished a batch of through-hole PCB's, and we're noticing a
severe red-brown rust like substance around and on our solder joints.  My
theory is that our batch washer cut out during the dry cycle because our
boards were fairly wet when checked.  The boards were sitting for an entire
weekend in this humid and wet state.  We're using two mixed bed DI columns
and get about 8-10 Megaohm water.

Could this perhaps be a lead oxide that formed due to the moist conditions?

Does anyone have any suggestions on how to clean this boards for recovery?
Alpha Metals is suggesting we add a saponifier.

Paul Wareham
DynaGen Systems Inc.