Dave, thanks for bringing the appendix to my attention. I had long wondered about ENIG and the gold thickness question.  Joyce's clear inquiry and the comments from you and Wayne were very helpful.  Louis Hart

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of David Hillman
Sent: Tuesday, August 11, 2015 5:27 PM
To: [log in to unmask]
Subject: Re: [TN] immersion silver

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,

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