Hi Kathy - there have been some wonderful comments mentioned already on
your tin oxide issue  and here is one more avenue to pursue! "White"
residue has been a historic assembly problem that in many cases were traced
to tin oxide created from solder joint/flux reaction being deposited on the
assembly during a waterbased cleaning process due to excessive water or
drying temperatures. The excessive temperatures create a reaction that
literally bonds the tin oxide to the laminate or soldermask and it takes a
stick of dynamite to remove the oxides (which unfortunately also removes
the rest of your assembly).  Get someone at IPC to find a copy of Technical
Paper TP-696 "The Nature of White Residue on Printed Wiring Assemblies" by
Dennis Bernier of Kester Solder (dated 4/1988). I need to point out this
reference is going to talk about rosin based fluxes - 1988 was a bit early
for the industry wide existence of  low residue fluxes - but some of the
physics that are discussed in the paper may be useful. Good Luck.

Dave Hillman
Rockwell Collins
[log in to unmask]





Kathy Palumbo <[log in to unmask]> on 11/25/98 05:51:39 PM

Please respond to "TechNet E-Mail Forum." <[log in to unmask]>; Please respond
      to Kathy Palumbo <[log in to unmask]>

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Subject:  [TN] Tin Oxide




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!!!

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