Hi Paul! There are three basic methods you can use to restore solderability
on components:

a) Use of highly active fluxes in a retinning operation
b) Use of a surface stripping chemistry and then a standard retinning
operation
c) Use of electrochemical conversion chemistry and then a standard
retinning operation

Keep in mind that none of the three basic methods will work on everything
and all three are highly dependent on just what/amount of finish remains on
the component lead and the amount of oxidation/corrosion that is on the
component lead. Highly active fluxes are good but if you don't get them
removed you can have problems later on the assembly. Surface stripping
chemistries work well (e.g. something like Kester's SolderNu) but you need
to be very careful on how the stripping chemistries attack the component
bodies. And stripping chemistries tend to be pretty specific to the surface
you are working with (e.g. is it copper, or nickel, or alloy 42, etc.).
Electrochemical conversion is great (I have two ROSA systems) but you need
to be concern about cleanliness and some surfaces can contaminate the
electrochemical cell (ROSA has an iron tolerance on the cathode grids which
requires periodic maintenance schedule attention). Hope this helps - good
luck.

Dave Hillman
Rockwell Collins
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Paul Truit <[log in to unmask]>@ipc.org> on 05/15/2002 12:41:25 PM

Please respond to "TechNet E-Mail Forum." <[log in to unmask]>; Please respond
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Subject:    [TN] Restoring solderability


With today's economic climate we have found that a few parts have been
sitting too long in inventory.  The solderability has been affected.
Specifically it was a two pin terminal block that was shipped to us in a
cardboard box and the part was pressed down into styrofoam. I believe
the sulfur from the cardboard box has out gassed and negatively affected
the part's solderability.

Is there a method to effectively and efficiently restore the
solderability?

TIA
--
Paul Truit, Mfg. Eng.
RBB Systems, Inc.
4265C E. Lincolnway
Wooster, OH  44691
Ph. (330) 567-2906 ext 514
Fax (330) 263-5324
Email: [log in to unmask]

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