All

Prof Bill Plumbridge's team of the Open University in the UK has published a
paper (Karyia et. al., Soldering and Surface Mount Technology, 2001, 13,
39-40) on the observation of tin pest in Pb-free solder (SnCu, I think)
stored in a freezer for an extended period.  I saw the samples and can
confirm that 'pested' tin is indeed a grey powdery mush and not to be
confused with metal at all!.

Regards

Jim
++++++
From:   James H Vincent
        Bookham Technology plc
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-----Original Message-----
From: EMTC Ireland [mailto:[log in to unmask]]
Sent: 25 May 2004 18:42
To: [log in to unmask]
Subject: [LF] Lead Free Wave Solder Alloy Temperatures


Hi all

In reference to Howard H. Manko's book "Solders and Soldering" I'm just
interested in learning from the metallugist fraternity out there his
description of "Tin Pest"
"When cooled to low temperatures, pure tin transforms from a white metallic
material into a grey amorphous powder. In the past this transformation was
called "tin pest", because tin articles for no explainable reason crumbled
into dust." (13.2degC)

The paragraph continues to describe detrimental properties of tin - but can
anyone comment for Sn0.7Cu or any high tin containing alloy if this is of
concern.

Also has anyone Phase Diagrams for the SnCu and SAC alloys that show the
"recommended alloy temperature during wetting" as presented in Manko's book
(Fig 3.8) as opposed to the rule of thumb approx 40degC above liquidus?


All information/references appreciated,
Thanks in advance
Moss

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