Hi Ed and Dave,
I ran into a similar issue back when I was in Tulsa. We were building
cabinets that had wire harnesses using braided shield wire that the shields
were silver plated copper. At the time we were using a water soluble no
clean (which we found out later that you really shouldn't use it as a no
clean). We built up a bunch of cabinets and had a rather rainy spring which
caused the humidity to stay high for several weeks. Eventually we started
seeing this on the braided shields:
http://stevezeva.homestead.com/files/Green_Junk_1.jpg
http://stevezeva.homestead.com/files/Green_Junk_2.jpg
http://stevezeva.homestead.com/files/Green_Junk_3.jpg
http://stevezeva.homestead.com/files/Green_Junk_Close.jpg
We switched over to Kester 951 which the datasheet says that it has a
"corrosion inhibitor" in the flux, and the green junk went away. Kester
also put out this paper on green corrosion, or Copper Abietate. Google:
Green Corrosion Kester.
Steve
On Fri, Nov 3, 2017 at 10:11 AM, David Hillman <
[log in to unmask]> wrote:
> Hi Ed - based on the details you provided, here is what I believe is
> happening - Many of the OA type fluxes contain a significant chlorine
> content and also consider you have a potential fluorine contribution from
> the flux interacting with the PTFE insulation. Copper loves to react with
> both Cl and F with the reaction producing a corrosion product that has a
> characteristic blue/green optical appearance. The corrosion product can be
> identified by its unique crystal structure using XRD techniques. It appears
> you are dealing with a case of poor cleaning as there is flux being trapped
> under the insulation and it is causing a corrosion reaction. One method of
> avoiding this issue is to carefully apply the flux to the stripped wire in
> such a manner as the flux does not contact the wired/non-stripped
> insulation interface. The best way to clean this is to not allow it to
> happen during the initial processing - trying to get that interface clean
> is difficult and hard to confirm "clean".
>
> Dave Hillman
> Rockwell Collins
> [log in to unmask]
>
> On Fri, Nov 3, 2017 at 10:39 AM, Ed Popielarski <
> [log in to unmask]>
> wrote:
>
> > Hi Technetters,
> >
> > I have 2 questions:
> >
> > 1: How is this oxide formed?
> > 2: is there a "safe" way to clean it after the fact?
> >
> > On very rare occasion, we have a "verdigris" outbreak on Tin plated solid
> > Cu wire. The insulation tends to not be well adhered (PTFE) when this
> > "breaks out" The stripped wire looks "normal" but when soldered with OA
> > flux (either hand or wave) it starts showing a blue-green oxidation at
> the
> > insulation/wire interface. Wetting is marginal at best. Scrapping the
> wire
> > and going to a different manufacturer usually resolves it, but there's
> > still labor involved since it doesn't show up until later in the process
> &
> > must be reworked.
> >
> > Thanks in advance!
> >
> > Regards,
> >
> > Ed Popielarski
> > Engineering Manager
> >
> > [cid:[log in to unmask]]
> > 970 NE 21st Ct.
> > Oak Harbor, Wa. 98277
> >
> > Ph: 360-675-1322
> > Fx: 206-624-0695
> > Cl: 360-544-2289
> >
> >
> >
> > "It's one kind of victory to slay a beast, move a mountain, and
> > cross a chasm, but it's another kind altogether to realize that the
> beast,
> > the mountain, and the chasm were of your own design."
> > https://goo.gl/maps/mMjg43rXeFB2
> >
>
--
Steve Gregory
Kimco Design and Manufacturing
Process Engineer
(208) 322-0500 Ext. -3133
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