Hi,
Copper Oxide may not be as big a problem as Copper chlorides especially if a
bias voltage is applied and some liquid moisture is present.  You would need
to evaluate the susceptibilty of your assembly to salt and moisture.  This
is probably only a concern if you are in a harsh environment. You can try a
real easy experiment by putting a 5-10V bias between two adjacent copper
conductors and place a drop of salt between them and let it sit for a while
and watch what happens.
Steph

*********************************************************
Stephan Meschter               [log in to unmask]
Lockheed Martin Control Systems  Phone  :(607)770-2332
600 Main Street, MD R52F         FAX    :(607)770-2056
Johnson City, NY 13790-1888      MARCALL: 8 * 255-2332
*********************************************************


> ----------
> From:         Michael Carano[SMTP:[log in to unmask]]
> Reply To:     TechNet E-Mail Forum.;Michael Carano
> Sent:         Wednesday, May 27, 1998 12:11 AM
> To:   [log in to unmask]
> Subject:      Re: [TN] HASL alternative.Exposed copper
>
> SteveZeva wrote:
> >
> > Hi Nicolas!
> >
> >      As far as the exposed copper that results from an OSP process,
> there
> > isn't an issue as far as I know. Yes the copper will oxidize, but from
> the
> > little bit I know about metallurgy, it's my understanding is that the
> copper
> > will be coated with a layer of oxidation, and then it slows down
> dramatically.
> > For a illustration of that just think about some of the copper water
> lines in
> > old houses, the copper telephone lines exposed to the elements for years
> and
> > years...that shows that it takes quite a while for copper to
> deteriorate.
> >
> >      Somebody correct me if I'm wrong about this, but the exposed copper
> > problems that are defects usually have something to do with the exposed
> copper
> > being an indicator of some other problem, not the fact that the copper
> itself
> > is exposed. Oxidation of the copper is normally only a problem when
> trying to
> > solder to it...
> >
> > C-ya,
> >
> > -Steve Gregory-
> >
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> additional information.
> > For technical support contact Hugo Scaramuzza at [log in to unmask] or
> 847-509-9700 ext.312
> > ################################################################Hi
> Nicolas,
> I have come across this question of the exposed copper with respect to
> OSP's. While solder paste spreading will vary from paste to paste and OSP
> to OSP, no one has ever(to my knowledge) determined that the exposed
> copper caused a long term reliability problem. Maybe Jack Crawford at
> the IPC can help with this one.
>
> Best regards,
>
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> ################################################################
>

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