Fear of antimony is something that I also have run into. In actuality, the
only "toxicity" related to antimony is antimony trioxide, which is a flame
retardant. Antimony trioxide is created during the sublimation of antimony
at 630 degrees C when it is non-alloyed. Antimony trioxide is not formed
during a soldering operation. This is not different than many other metals.
Tin, know to be a “safe” metal, is toxic in all forms of organic compounds
at .1 mg per cubic meter of air, and in inorganic forms at 2 mg per cubic
meter of air.
However, we all know by now that the outlawing of elements is not
necessarily dependent upon science- much more often it is politics and/or
legislation. I believe that the key to the antimony argument is that there
is no legislation, pending legislation, or propositions regarding antimony.
The EPA does not even recognize it as an element necessary to be tested for
in TCLP testing, unlike lead (and even silver!). This is the big difference
between antimony and lead, or for that matter copper and lead.
For additional information about antimony, refer to the U.S. Department of
Health & Human Services toxicological profile # TP-91/02. I'm looking
forward to the ensuing comments!
-----Original Message-----
From: Alan Rae <[log in to unmask]>
To: [log in to unmask] <[log in to unmask]>
Date: Thursday, September 16, 1999 8:35 PM
Subject: [LF] IPC review September 99 - Antimony and Bismuth in Lead-Free
Solders
>"Filling up on unleaded"
>
>Coming originally to this forum from the metals side - I worked for 4 years
in
>the antimony business in the '80's- I'd just like to add some perspectives
on
>the use of antimony and bismuth based on some of the comments I keep seeing
in
>articles on lead-free solder including the above saying that they're
"toxic" or
>"unavailable".
>
>Concerns are being raised about the toxicity and availability of these
materials
>and I'm not sure they're well founded. By the way, my employer and I are
not
>involved except in the periphery of the antimony or bismuth business so I
have
>no commercial ax to grind. If customers want alloys containing these
materials
>we can supply them; if they don't want them, that's no problem either. The
>following are my personal perceptions so they're obviously open to
comment,
>debate, interpretation, correction etc.
>
>Bismuth first. Bismuth is indeed a by-product of lead refining but I do
not see
>lead consumption falling because of the increasing use of lead-acid
batteries.
>These account for about 80% of the use of lead and have a recycle ratio
near
>100%. As we move to hybrid and electric vehicles I don't see a technology
to
>immediately replace these batteries and I see a growing lead consumption.
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?
>
>Now antimony, which is a by-product of not only lead but also gold and
other
>metal production. Again, no shortage; a continued use in lead-acid
batteries as
>a plate stiffener and the major use as a flame retardant, especially in PVC
in
>your house, office and automobile. Remembering my chemistry, I believe
antimony
>is one of those funny amphoteric oxides which are insoluble in strong acid
(i.e.
>stomach acid) but are quite soluble in neutral pH e.g. in ground water
>leachability tests. There are concerns, particularly in Europe, on the
>inhalation of the oxides. 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?
>
>In both cases, if you are aware of any data that prove the above to be
wrong,
>please let me know.
>
>All metals or their compounds can be labelled toxic. In our circuit board
>materials, many tin, silver and copper componds are toxic, if not to
humans, to
>fish, invertebrates, vegetation or other life forms; glass fibers aren't
great
>to inhale(I've tried) and the last pot of epoxy I used in airplane
construction
>came with a MSDS that looked as if it had been written by Tolstoy! Copper
oxide
>is used as a wood preservative. Tin organics can be used in antifouling
paints.
>Remember salt that is essential to your life is made from chlorine, once
used as
>poison gas, and sodium, a spontaneously-flammable metal. And that's before
we
>get into the materials used in semiconductor processing!
>
>I think we need to be very careful before we unwittingly damn any of our
>technology choices in public because of toxicity or availability - and get
the
>facts. I'm not saying antimony or bismuth are safe - but let's make a
realistic
>assessment based on their actual life cycle before we label them "toxic" or
>"unavailable". Absolutely we need to be good stewards of the environment
but
>let's not paint ourselves into a corner by eliminating useful technology
>needlessly. If metals are deemed to be toxic, isn't a takeback and reclaim
>program a more practical solution than banning them needlessly? Even the
>electric toothbrush I bought this weekend has a clearly explained takeback
>mechanism for the Ni-Cd batteries that are hermetically sealed in plastic!
>
>As I said, let's get the facts. The move to lead-free has so much momentum
it's
>probably unstoppable. With other critical materials that are less in the
public
>eye let's get a proper environmental assessment. Let's not make sweeping
>comments in widely read papers before we've done that. They will be read
and
>people will naturally say hmmm - here's a material to add to our list to be
>banned.......
>
>I hope you find these comments useful and would welcome your feedback.
>
>
>_________________
>Alan Rae
>Director of Technology
>Cookson Electronics Inc.
>225 Foxborough Blvd. Suite 150
>Foxborough MA 02035
>USA
>[log in to unmask]
>Phone: (508) 541-5843
>Fax: (508) 541-5877
>
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################################################################
IPCWorks -October 25-28 featuring an International Summit on Lead-Free Electronic
Assemblies.
Please visit IPC's Center for Lead-Free Electronics Assembly
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For technical support contact Gayatri Sardeshpande [log in to unmask] or 847-790-5365.
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