Ron,
An excerpt from a report I wrote.
a-Tin, commonly known as grey-tin or tin-pest is an allotropic form
of tin. Researchers have found that tin can change form at low temperatures
and become a powdery wartlike structure. The powder has no strength and is
a pure form of tin crystal.
Tin plate or tin lead solder requires an inoculation with a-Tin to initiate
the transformation. However, once started, a-Tin will continue to grow,
completely consuming a joint. One researcher suggest small amounts of
antimony or bismuth will prevent the nucleation of a-Tin.5
5. Phillip E. Hinton, "Tin-Plating, Tin-Nickel Electroplate and Tin-Plating
over Nickel as Final Finishes on Copper", SMI 1996, p807.
Given the above statement, it is unlikely that the white powder you saw is
a-Tin. But if there were no chemicals involved at that site, it is
something that makes you go hmm.
Thanks
Ryan Grant
Advanced Technology Engineer
MCMS
(208) 898-1145
[log in to unmask]
> -----Original Message-----
> From: Hollandsworth, Ron [SMTP:[log in to unmask]]
> Sent: Friday, August 04, 2000 6:27 AM
> To: [log in to unmask]
> Subject: Re: [TN] Alpha Tin
>
> Ryan:
> Refresh my memory on Alpha Tin, if you would please.
>
> Ron
>
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