In a message dated 11/25/98 3:53:54 PM Pacific Standard Time,
[log in to unmask] writes:

<< I am having a cleaning problem.

 We use a liquid, water soluble touch-up flux to assemble a module.  When the
 module is complete we run it through an in-line cleaning system.

 When the modules are inspected there is still yellow crusty residue left on
 the module.  We have sent the modules out to a lab and their analysis shows
 that the crusty residue is a form of tin oxide.

 We beleive this tin oxide is not soluble and can not be cleaned with any
 thing, and in order to eliminate this tin oxide residue we must eliminate
 oxygen in the assembly process and use Nitrogen (N2).

 Does this sound correct?

 Is their anyone out there who could help steer me in the right direction?

 Thanks for your help in advance!!

 Kathy Palumbo

 PS  Have a Happy and Safe Thanks Giving Holiday!!!
  >>

Kathy,

Does this residue remain around the periphery of the solder joint? Right
around the outside edges? I may have seen this too and was told that it could
be Tin Carboxilates?!? (whatever that stuff is) Basically, I was told that I
probably was staying liquidous too long or too high in my peak temperature
during reflow. I was also told that wash temperatures that are on the high
side (120 degrees F. +) will exacerbate the problem. I re-profiled my reflow
oven and lowered the wash temperature down to 110 degrees and it went away.
It's not ionic, is it? Just looks like crap, huh? I don't know if it's the
same deal with you that I had, but it's something to eliminate....

-Steve Gregory-

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