This email is to clear some misinterpretations and incorrect extrapolations
that has resulted from an article I authored in the IPC Review ("Filling Up
on Unleaded").

Lead-free forum:  "So bismuth should not be in short supply. Apparently the
major commercial use of bismuth is as compounds such as bismuth salicylate
which are used in large quantities as stomach medicine (by those worried
about the switch to
lead-free?). In fact it's the major use of bismuth.  So - why are we worrying
about its toxicity?"

Response: "Should not be" doesn't equal isn't. Nevertheless, the article does
not say the supply of bismuth is limited. Rather, it says "Some exotic
materials are hampered by their regional availability; for instance, bismuth
is found mainly in China." The point here is that since China is a political
hot spot, it might not be best to rest the electronics industry's well-being
on bismuth.

The National Center for Manufacturing Sciences conducted a 4-year, $10
million study into lead free alloys. The results were published in 1997. This
is directly from the NCMS report:  "Bismuth is a relatively benign metal with
a history of medicinal uses. The forms of Bi used (organic and inorganic
compounds) do not generally allow appreciable levels of assimilation of
elemental Bi in the body. Bismuth is very similar to Pb and is adjacent to Pb
in the periodic table indicating that they might have similar properties as
sister compounds. In the past, the primary source of Bi was as a byproduct of
lead smelting; therefore, increased use of Bi could increase the production
of a hazardous waste (Pb) that has well documented environmental and health
concerns."

Lead-free forum: "Now antimony...Again, no shortage."

Response: The article does not comment on the availability of antimony. In
fact, it quotes prices from an article in Circuits Assembly that said Sn-5Sb
one of two alloys closest to Sn-37Pb in price. From this, one could infer
that Sb is relatively abundant.

"But antimony is used widely in our daily lives with no apparent ill effects
that I am aware of - so why are we so worried about its toxicity also?"

Response: The NCMS report says "Antimony is highly toxic when inhaled or
ingested and has the same Lethal Dose, Lower Limit (LDLo) as Cadmium.* It
should not be considered as a possible major constituent in solders. Antimony
has been present in military solders since the 1940s, but only insmall
amounts, typically less than 0.5%. Since low concentrations of Sb adversely
affect solder alloy properties, the widespread use of solders with higher
concentrations of Sb is not anticipated."

*The report also says "Cadmium should not be used, even if Cd-contain alloys
are the only alloys that meet the project's overall manufacturability and
reliability goals. Cadmium is regarded by the International Agency for
Research on Cancer as a carcinogen."

That's pretty damning testimony, and the companies who sponsored and
conducted the research include many of the largest OEMs in the US, including
Hughes, Rockwell, Texas Instruments, Lucent, and others. Thus, you can see
why my reporting is influenced by it.

I'll add that the report notes: "Lead was identified as the most toxic
element relative to the other elements in the evaluation because of the large
history of human lead toxicity problems and its documented impact on the
young and elderly, even though its Toxic Dose, Lower Limit (TDLo) is higher
than all other elements with the exception of Sn."

I agree that lead in electronics is getting a bum rap. But I'm also seeing
questions raised in this forum that do have scientific answers--even if they
are not the answers we've been raised on.

Mike Buetow
Editor, IPC Review

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