Paul,

I once experienced a similar problem with orange to red colored residue on
solder joints.  In that case, copper from the piping on a vapor degreaser was
leaching into condensed moisture in the system.  We did EDS and found it was
copper that produced the orange-red reside.  It was most likely plating out of
solution due to a displacement reaction (similar to electroless plating).

If you'd like to discuss this off-line please call me at 425-335-4400 or email
at [log in to unmask]

Best Regards,
Ed

David D Hillman wrote:

> 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
> [log in to unmask]
>
> Paul Wareham <[log in to unmask]> on 01/15/99 03:00:29 PM
>
> Please respond to "TechNet E-Mail Forum." <[log in to unmask]>; Please respond
>       to Paul Wareham <[log in to unmask]>
>
> To:   [log in to unmask]
> cc:
> 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.
>
>

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