Phil,

    You can also check an article written by Duane Endicott of Motorola,
"The Challenge of a Lead-Free Finish for Semiconductor Pins" which appeared
in the Jan. '97 edition of Metal Finishing magazine.  In his article, Duane
describes the three criteria for an alloying metal of Sn to be successful in
preventing whiskers.  These are:  (1) it must have an atomic diameter 15%
greater than that of tin, (2) it must be mobile in the tin crystal lattice,
and (3) it must not form an intermetallic compound with tin.

    Applying these criteria to Cu indicates that it should not be sufficient
to prevent tin whisker growth, since Cu does form intermetallics with tin.

  Regards,
        -Rob Schetty
        LeaRonal Inc..
        Freeport, NY, USA




-----Original Message-----
From: Phillip E. Hinton <[log in to unmask]>
To: [log in to unmask] <[log in to unmask]>
Date: Tuesday, February 03, 1998 10:32 PM
Subject: [TN] Whiskers with Sn99.3


>All
>Subject: Solder Sn99.3/.7Cu and whiskers
>
>I have been experimenting with one of the no lead solders, Sn99.3/Cu.7, and
it
>appears to have many of the attributes that are desired for a particular
>product; however, I have not been able to find any literature or recent
>information on its resistance to tin-whisker growth.  If you have any
>information or leads I would appreciate it.
>
>Thanks,
>Phil Hinton
>[log in to unmask]
>520-745-1013
>
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