Hi gang - Wayne, you are faster than I but I can add some additional
detail. In Appendix A of the IPC-4552 specification, there are the
definitions of "electroless" and "immersion" which mirror Wayne's details
but with more words. The definitions were added to the specification
because Joyce's question is very common.

Dave

On Tue, Aug 11, 2015 at 4:15 PM, Wayne Thayer <[log in to unmask]> wrote:

> 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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