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The Tin-Whisker Menace
An anonymous reader writes "Fortune has an article about how the recent environmental push to completely eliminate lead from electronic components and wiring may eventually lead to the next Y2K problem of slowly-growing tin whiskers short-circuiting equipment.""
it's more disposal than consumer protection... tons of lead in a landfill isn't good
I quote from a most informative pdf (get it here):
"A tin whisker is a single crystal of tin that grows spontaneously from a surface a pure tin. They are typically only a few microns (?m) in diameter but can grow to lengths of more than 10 mm (though lengths on the order of 1 mm are far more common) [NIST Website, 2002]. Tin whisker growth is spontaneous, not relying on external influences of current or electrolytic action, more commonly associated with mechanisms like "dendritic" growth, conductive filament formation and electromigration. While early studies believed that tin recrystallization (which occurs at 50 deg C) played some role in whisker formation, recent studies have reported as much, if not greater, propensity for whisker formation at temperatures as low as room temperature [NASA Web Site, 2002].(....)Conventional wisdom attributes tin whiskering to internal stresses in the pure tin layer, with a primary source being the compressive stresses caused by electroplating. However, tin whiskers have also been reported from surfaces where tin has been applied by methods other than electroplating. In the presence of compressive stress, whiskers are extruded over time, as a stress release mechanism. Many factors may contribute to the stress in the plating, including intermetallic formation, thermal expansion mismatches, corrosion of the substrate, and externally applied forces such as bending, lead forming and application of pressure. Defects such as scratches and nicks have been reported to magnify the effects by causing local stress concentrations and possibly providing openings in any protective surface oxide layers. In fact, these external factors may cause whiskering in samples that may otherwise be resistant to the phenomenon. For example, tin whiskers have been observed to form on tin finished surfaces that had been exposed to hot oil dip to fuse the tin (a known mitigating process) [Cunningham and Donahue, 1990]. Adding a trace amount of another element (i.e. Pb or Bi) has been shown to reduce the tendency of plating to grow whiskers."
----- One learns to itch where one can scratch.
OK, I'll feed the troll.
Lead is a neurotoxin; children exposed to lead are at risk of developmental delays, reduced IQ, learning disabilities, hearing loss, reduced height and hyperactivity. Levels above 10 mcg/dL (about 100 ppb) are considered to be a health risk to children. Adults are at risk of anemia, nervous system dysfunction, kidney problems, hypertension, decreased fertility, and increased level of miscarriages.
It used to be that the biggest source of environmental lead was automobile exhaust, followed by lead paint. In the late 1970's 14.9 million children in the US had elevated blood lead levels. This figure declined to about 300,000 in the US CDC's 99-00 survey. Banning lead paint in 1978 and leaded gasoline's phase out starting in 1975 removed the sources of exposure.
In adults, levels above 24 mcg/dL are considered elevated and mostly come from workplace exposures, such as demolition, recycling and manufacturing. The number of adults with elevated blood lead levels has also been declining.
The problem with adult exposure is that without proper industrial hygiene, the lead comes home with them, providing a route of exposure to their children. 2-3% of children with elevated blood lead levels are exposed in this way.
Lead in manufacturing is an expense since exposure has to be managed. But, if you don't control it at the source, then you have to try and manage it in the waste stream which is much more expensive and difficult. Given the population density and the emphasis on recycling in the EU, lead exposure through this route is a decreasingly acceptable risk to the population.
P.S. The EU is the largest economy in the world so you tell your directors that you don't need that market anymore!