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September 2001

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From:
Mike Fenner <[log in to unmask]>
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Date:
Wed, 26 Sep 2001 14:05:06 +0100
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Electroless Nickel Immersion Gold

The copper tracks are plated with nickel (no more than say 5 microns - sorry
don't do micro inches -  and then the nickel is protected by a thin layer of
gold.  (usually less than a micron say 0.5u)

Best regards

Mike Fenner
Applications Engineer, European Operations
Indium Corporation
 T: + 44 1908 580 400
M: + 44 7810 526 317
 F: + 44 1908 580 411
 E: [log in to unmask]
W: www.indium.com
Leadfree: www.Pb-Free.com



-----Original Message-----
From: TechNet [mailto:[log in to unmask]]On Behalf Of Louis, Edwin @ CSE
Sent: Wednesday, September 26, 2001 1:34 PM
To: [log in to unmask]
Subject: Re: [TN] White Immersion Tin


What is ENIG.?

-----Original Message-----
From: Steve Kelly [mailto:[log in to unmask]]
Sent: Tuesday, September 25, 2001 3:49 PM
To: [log in to unmask]
Subject: Re: [TN] White Immersion Tin


I apologize to the Tech-net - I inadvertently sent out the wrong e-mail.

I can add some feedback on immersion tin. We have neen running for over 2
years. The process does give a very good flat solderable surface and is a
much easier process to control than ENIG. However it is very aggressive on
soldermasks and dislikes thermals. We even silkscreen before we put down the
immersion tin so we have the freshest surface available for soldering.

Regards Steve Kelly

-----Original Message-----
From: TechNet [mailto:[log in to unmask]]On Behalf Of Neil Atkinson
Sent: Tuesday, September 25, 2001 3:48 AM
To: [log in to unmask]
Subject: Re: [TN] White Immersion Tin


The advantages and disadvantages of immersion tin have been well covered in
the TechNet in the past so it may be worth checking the archives.

Anyway, for what it's worth here's what I have found with experience / what
I have heard.

Key advantages are it is flat, relatively cheap, easy process to install and
control and, in my experience gives reasonable solderability even after
storage provided the boards are reasonably well packaged.

As for disadvantages, I have seen instances where the chemistry used for the
immersion tin has attacked the solder resist and exposed copper, I'm not
sure how environmentally friendly the chemistry is (although I am sure
someone will now answer this!!).

Overall, it depends what you want, no doubt someone will say ignore it and
go for NiAu or HASL but I would say that it is a good general alternative to
HASL and even in some cases NiAu (e.g. can carbon be used for any
contacts?).  If you haven't tried it I would say try it and use it where the
price / performance ratio seems to be in favour of it.

It does not suffer from whisker growth because it's structure is such that
it reduces stresses in the material which cause growth (apparently!!).
However, one question which I would ask is if anyone knows whether if white
tin is put under mechanical stress e.g. by use of press fit connectors, can
it then produce tin whiskers?

One problem I have seen is with tin being slivers being produced by
press-fit connectors resulting in shorts.

Neil

Neil Atkinson - Quality Manager
Stadium Electronic Controls Division
Stephen House, Brenda Road, Hartlepool (UK) TS25 2BQ


                -----Original Message-----
                From:   Louis, Edwin @ CSE [mailto:[log in to unmask]]
                Sent:   24 September 2001 14:49
                Subject:        White Immersion Tin

                What are the advantages and disadvantages of Whit Immersion
Tin for PCBs?
                Are there dendritic growth possibilities?
                What thickness minimum should you have?

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