Piotr,
The information on tin pest (tin plague, tin leprosy, tin disease) is
still rather sketchy, although it has been known since the late 1800's.
In my now-347-page Bibliography for Designing Lead-Free, RoHS-
Compliant, and WEEE-Compliant Electronics (I had to add a 10th
file-cabinet drawer for my reference collection this weekend), at
   http://www.dbicorporation.com/rohsbib.htm
I think I have fewer than 20 books, papers, reports, magazine articles,
and web pages that discuss tin pest.

The earliest references that I have personally found to tin pest are:
*  Louis, Henry, Metallurgy of Tin. New York: McGraw-Hill, 1911, pages
   1-3.
*  Cohen, Ernst, "Infected tin or the "tin-pest"," Journal of the
   Franklin Institute , vol. 173 no. 5, pp. 531, May 1912.

Two papers on tin pest in lead-free solders are:
*  Kariya, Yoshiharu, Gagg, Colin, and Plumbridge, William, "Tin pest in
   lead-free solders," Soldering & Surface Mount Technology, vol. 13 no.
   1, pp. 39-40, 2000.
*  Kariya, Yoshijaru, Williams, Naomi, Gagg, Colin, and Plumbridge,
   William, "Tin Pest in Sn-0.5 wt.% Cu Lead-Free Solder," JOM, vol.
   53 no. 6, pp. 39-41, June 2001.

From everything that I have read, once tin pest begins, the only way to
stop it completely is to melt the material down and start all over
again...  I'm still searching for information on whether tin pest will
continue at temperatures above 13 degrees C once it has started, or
whether it only progresses at temperatures below 13 degree C.

I have seen a few documents that say that as little as 0.2-0.3% of lead
in a tin alloy will prevent tin pest.  But this is well over the 0.1%
lead permitted by the first amendment to the RoHS Directive (2002/95/EC,
   http://europa.eu.int/eur-lex/pri/en/oj/dat/2003/l_037/
   l_03720030213en00190023.pdf

   http://europa.eu.int/eur-lex/lex/LexUriServ/site/en/oj/2005/
   l_214/l_21420050819en00650065.pdf   )

If I was manufacturing/selling a lead-free product, I'd be extremely
reluctant to provide a warranty longer than *1 year*, because of
concerns with:
*  Tin whiskers, causing short circuits.
*  Tin pest (tin plague, tin leprosy, tin disease), causing opens when
   the solder turns to dust at temperatures below 13 degrees C.
*  Sensitivity to physical shock, causing opens when a product is
   dropped even a short distance onto a hard surface.
*  Kirkendall voids, causing opens.
*  Conductive anodic filaments (CAF), causing shorts *inside* printed
   circuit boards.

I've been recommending to our clients that they not make a whole-hog
commitment switching their products to lead-free/RoHS-compliance, if
they don't have to.  If they have lead-containing products that are in
production, and can remain in production for some time without parts/
processes going obsolete on them, consider leaving them among their
product offerings.  Then, if as I fear, many lead-free products turn out
to be unsafe-- killing and injuring people, burning down buildings,
etc.-- in addition to being short-lived and unreliable, the company will
still have products that it can sell in most of the world.  And maybe it
won't go bankrupt, while the companies that switched all their products
to lead-free find that they can't sell any of their products anywhere in
the world...

If it is any consolation, the (European) Product Liability Directive (
Directive 85/374/EEC,
http://europa.eu.int/eur-lex/en/consleg/pdf/1985/en_1985L0374_do_001.pdf
) says in Article 7:
     "The producer shall not be liable as a result of this Directive if
     he proves:
     ...
     (d) that the defect is due to compliance of the product with
         mandatory regulations issued by the public authorities; ..."

At the personal level, when it is your own money you are spending, since
April 2005 I have been recommending to friends and co-workers:
1.  Don't buy any *new* electronics between January 2006 and June 2007.
2.  If given a choice between a RoHS-Compliant product and one that
    doesn't claim RoHS-compliance, buy the latter.
3.  If offered an extended warranty, buy the longest one available...
    and hope that the company offering it stays in business long
    enough to replace your unit when it dies within the warranty period.
4.  If you are replacing a working unit, and have the space and can
    afford it, KEEP YOUR OLD UNIT SO THAT YOU STILL HAVE SOMETHING
    TO USE WHEN THE RoHS-COMPLIANT UNIT DIES.

John Barnes KS4GL, PE, NCE, NCT, ESDC Eng, ESDC Tech, PSE, SM IEEE
dBi Corporation
http://www.dbicorporation.com/

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