Hi Grunde - the primary issue is that all plating chemistry formulations
have a deposition range that they should be operating within and if you are
either "under driving " or "over driving" the plating bath you end up with
a damaged plating deposit. Some of the root cause for the early Black Pad
issues with ENIG plating systems was that folks were pushing the plating
deposition reactions beyond they functionality (aka too thick) causing all
sorts of problems. The IPC-45XX committee has done a tremendous amount of
work and education attempting to get people to understand that plating
chemistry formulations must be operated in a correct manner. You can
directly correlate many surface finish plating issues with someone trying
to drive a plating deposition beyond its limits.

Dave

On Wed, Aug 12, 2015 at 7:27 AM, Grunde Gjertsen <[log in to unmask]
> wrote:

> Hi
>
> Could that relate to the Uyemura TWX-40? Supposedly a hybrid bath for
> plating thicker gold without damaging the nickel?
> It doesen't make sense for manufacturers to apply thicker gold electroless
> when they can use a simpler immersion process, why would anybody do that?
>
> BR
> Grunde
>
> -----Original Message-----
> From: TechNet [mailto:[log in to unmask]] On Behalf Of Guy Ramsey
> Sent: 12. august 2015 13:02
> To: [log in to unmask]
> Subject: Re: [TN] immersion silver
>
> Very interesting addition to this discussion.
>
> -----Original Message-----
> From: TechNet [mailto:[log in to unmask]] On Behalf Of Wayne Thayer
> Sent: Tuesday, August 11, 2015 5:16 PM
> To: [log in to unmask]
> Subject: Re: [TN] immersion silver
>
> Hi Joyce-
>
> I thought perhaps someone smarter than me would give a carefully thought
> out response to your intelligent question, but it seems it was ignored, or
> went into my auto-junk machine, or maybe I've gone blind.
>
> Anyway, at some point in the 2000's the definition of "Immersion plating"
> got changed. I believe this happened because the immersion plating of your
> definition was extremely easy to use and care for. So people asked for
> "immersion" and the salesmen started claiming that finishes were "immersion"
> when they were actually "electroless" (which are a pain in the rear to
> apply, manage, and dispose of). I think Uyemura was the first to do this,
> advertising a thick "immersion gold". I remember going to their booth at
> IPC that year and trying to figure out what was going on, and when I did my
> impression was the salesman hid behind the "language barrier".
>
> So "immersion" now means any plating which uses no electrodes, and is put
> on "kind of" thin through careful process control.
>
> Wayne
>
> -----Original Message-----
> From: TechNet [mailto:[log in to unmask]] On Behalf Of Joyce Koo
> Sent: Tuesday, August 11, 2015 12:08 PM
> To: [log in to unmask]
> Subject: Re: [TN] immersion silver
>
> gurus, I need some education: Immersion process what I know of is surface
> ionic exchange process, once it covered surface, the chemistry stops, so it
> is a self limiting process.  What is thin and thick?  you means it can
> really gets thicker like electroless type?  not self limiting?  Many thanks.
> Best regards,
>                            jk
> > From memory the "thin" and "thick" silver finish classes recognised
> > that there were two competing but roughly equally popular IAg
> > chemistries in the industry , each with their own process max-min
> > deposit thicknesses and one typically thicker than the other.
> >
> > Clearly it didn't make sense for an IPC spec to have a "barn door"
> > range from minimum "thin" to maximum "thick", hence two ranges
> > defined. I don't recall one being "better" than the other because of
> > the thickness
> >
>
>
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