David Nebenzahl wrote in message
.com...
On 4/24/2010 9:17 AM N_Cook spake thus:

This is a reasonable start, certainly autoritive but nothing about
in-service vibration and/or temperature on PbF embrittlement

from 2006

http://ntrs.nasa.gov/archive/nasa/ca...268_2008037503.
pdf
DEVELOPING A NASA LEAD-FREE POLICY FOR ELECTRONICS
LEARNED LESSONS
Michael J. Sampson
MD, 20771, USA
National Aeronautics and Space Administration, Goddard Space Flight
Center,
Greenbelt,

[...]

Pure tin termination finishes shall be avoided whenever possible and
shall be carefully mitigated against the risk of whisker growth if
their use is unavoidable.

So how the hell does one mitigate against the growth of tin whiskers?


--
The fashion in killing has an insouciant, flirty style this spring,
with the flaunting of well-defined muscle, wrapped in flags.

- Comment from an article on Antiwar.com (http://antiwar.com)


Its called traditional eutectic Lead-Tin solder. Even the late-mediaeval
church organ builders were aware of tin-pest, even if they thought it was
the work of the devil. All RoHS compliant components are now tinned with 100
percent tin so the mitigation there is having to strip it off, mechanically,
or a nice "ring of death " develops.
The first time you go round minor components on a vibration/temperature
affected RoHS board giving a gentle tug, to the leads of 1/3 W resistors or
wire links say, with a pair of thin-nose pliers, is quite an eye opener.
Whether tin-pest (and consequential expansion) or lack of wetting I don't
know, but you never used to see that problem


--
Diverse Devices, Southampton, England
electronic hints and repair briefs , schematics/manuals list on
http://diverse.4mg.com/index.htm