Hi Richard - one reference book on tin that you may find helpful is:

"The Electrodeposition of Tin and its Alloys" by Dr. Manfred Jordan, ISBN
3-87480-118-7

The book covers much more than just the plating aspects of tin.

Dave Hillman
Rockwell Collins
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Richard Weiner <[log in to unmask]> on 02/10/2000 01:09:14 PM

Please respond to "TechNet E-Mail Forum." <[log in to unmask]>; Please respond to
      Richard Weiner <[log in to unmask]>

To:   [log in to unmask]
cc:

Subject:  Re: [TN] White Tin PWB



Jorge,
        We are currently using "immersion white tin" very successfully. The nice
thing about it from our fab house point of view is that it runs through their
normal line process. They have strongly encouraged it. We like the very flat
surface and have been using it in place of immersion gold. We are being
encouraged to try using it in some of our RF layouts but the engineers are
apprehensive about using tin in high frequency applications. I don't completely
understand the issues.
        One word of caution. We also design PCBs with large metal areas that
contact and ground machined aluminum covers and shields for EMC. We need very
flat surfaces to get a good contact seal between the covers and the PCB. Since I
have been unable to get good information on the long term oxidation effects of
the tin. I am afraid of an oxidation  build up over time causing resistance and
or surface abnormalities between the metal covers and the tin. Of course pads
and other metal areas are either covered with solder or soldermask so the tin is
not exposed to the air for oxidation.
        Hope this helps.

Richard Weiner

-----Original Message-----
From: Jorge A Rodriguez [mailto:[log in to unmask]]
Sent: Thursday, February 10, 2000 8:02 AM
To: [log in to unmask]
Subject: [TN] White Tin PWB


We are about to start using immersion tin PWBs (white tin) ,  the boards we
currently use are HASL and OSP. Are there any changes with the SMT process,
component termination finish or reflow process when white tin boards are used. I
know that white tin provides a better pad finish than HASL, similar to OSP, but
wihout the organic coating.  Any comments.


Any iformation would be appreciated.


Jorge Rodriguez
Process Engineer
Conexant Systems Inc

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