Jim:
The allotropic transformation of tin, tin pest, occurs at 13 C. However, at
this temperature, the conversion time is exceedingly long (decades).
Various experiments have been performed to accelerate the transformation
process. In general, -40 C is considered the temperature at which
transformation occurs the fastest. At this temp, transformation can be a
matter of days or decades depending on the factors you mentioned below.
Note that transformation is also highly accelerated if alpha tin already
exists or another material with the same structure as alpha tin is present.
Cheers,
Bob Hilty, Tyco Electronics
-----Original Message-----
From: Leadfree [mailto:[log in to unmask]]On Behalf Of Jim Chessman
Sent: Wednesday, June 30, 2004 11:21 PM
To: [log in to unmask]
Subject: [LF] tin pest
Hello, LF'ers:
Regarding the discussions of "tin pest" that took place on this forum
recently, I find myself left with a question:
Is the tin pest phenomenon cause for concern for Sn99.3/Cu0.7 solder? As I
recall from the discussion, certain alloying elements (such as silver,
bismuth, and --of course-- lead) all but eliminate "tin pest" at any
reasonable temperature, while other alloying elements (such as copper),
merely reduce the temperature at which tin's crystalline structure changes
from beta to alpha. So how cold can Sn99.3/Cu0.7 get before it starts to
succumb to "tin pest"?
James M. Chessman, Test Engineer
Reptron Manufacturing Services, Gaylord
1746 O'Rourke Blvd
Gaylord, MI 49735
Direct Phone: (989) 705-3149
<[log in to unmask]>
Horse sense is the thing a horse has which keeps it from betting on people.
-- W. C. Fields
God Bless America!
Please note: All *@kbyte.net e-mail addresses are have been changed to
*@reptron.com.
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