Carey
OK, I may have let my feelings and the necessary brevity of my posts
give a bad impression which was on the limit of politically correct and
I apologise for this.
I have had, in the past, a very good relationship with the ITRI. When
Colin Thwaites was in office and, to a lesser extent, his successors, I
always admired their objectivity and the enormous amount of help they
offered the electronics industry. What I was trying to say was that it
seems that their promotion of lead-free solder appears to show that they
have entered now into the political arena by going far beyond their
helping the electronics industry: in fact, doing it a disservice. This
is why I question their objectivity.
I agree that metals and their salts do not have the same toxicity. I
maintain that they are all toxic, even sodium, potassium, calcium and
iron which are all present and essential, amongst others, in our bodies.
An overdose of any will kill us. To the best of my knowledge (and it is
admittedly feeble), tin, if it is present, is in most organisms only in
trace quantities. I therefore suggest that an excess would be harmful,
even if there is a reasonable tolerance. Medical art (it is never an
exact science) and toxicology can never give exact figures and they have
consistently made optimistic errors which have had to be corrected. For
example, if you are as old as I am, you will remember when carbon tet
was safe to use with the operator's nose over an open tank. Then
restrictions started, leading eventually to a total ban. The same
scenario has been repeated time and time again. A similar situation
relates to environmental emissions which are always becoming
progressively tighter.
As for organometallics, these are relatively rare beasts. It all depends
on whether the metal is covalently or ionically bonded, I believe (the
latter are not true organometallics but organic metal salts). I
understand that, in nature, there is only one single organometallic,
namely vitamin B12 which has a single cobalt atom stuck right in the
middle of a very complex molecule, C63H90CoN14O14P. In the case of tin,
as I stated, they are used as various x-icides. But inorganic tin salts
are not exactly benign. For example, tin halides in both oxidation
states are used as complexing agents with transition metals in mordants,
etc. With this property, the toxicology must become quite complex (no
pun intended).
As for the 5 g of tin salts, you must have much more faith in the
regulating authorities than I do :-)
Finally, I should like to state that I am neither politically ecologist
nor an activist of any size, shape or form. I do pretend, however, that
I am environmentally conscious, but with my feet firmly on the ground. I
have been active, even proactive, concerning ozone depletion in the
sense that I have sat on committees dealing with the problem. The real
problem, I feel, is that there are many persons who emotively equate
lead in fuels and paint with lead in all forms and wish to say: thou
shalt not use it, with no thought to the consequences. I say these guys
have their heads in the ozone layer and their feet no more than 2 m
under it. Using anything responsibly is our duty and then we won't need
technocrats dictating to us what we should or should not use, without
the slightest idea of the consequence of their actions. If this is
'harsh', then you will find I'm likely to remain harsh.
Sorry for the length.
Brian
Carey Pico wrote:
>
> Brian
> I am surprised by your hashness in your last few e-mails. It resonates to
> me similar to the response much of the public gives "irradiated" vegetable
> produce in which they believe it makes it radioactive (it does not). It is
> emotional and without understanding.
>
> For the record, I have recently been asking a different PWB group as to why
> bother with getting lead(Pb)-free solders. But that is not what I am
> discussing here:
>
> One cannot label Pb as just one other metal and that health advocates will
> regulate them all out of existence. There are different toxicities of
> different atomic elements and molecules on a case by case basis. Pb is one
> element known to particularly harmful in small doses over a long period of
> time. There are others, for example cadmium(Cd) or Hg, but other metals are
> not (e.g., iron or gold). Organometallic compounds need to be evaluated on
> a case by case basis as well. Unfortunately, we (industry and government)
> don't have the resourses to test each one, so one draws on general chemical
> understanding and classifications to ascertain which molecules are expected
> to be harmful. My guess is that tin by itself is not harmful in small
> quantities, but their organometallics associates may be more of a threat
> based on chemical structures and electronic similarities. A good example is
> nickel carbonate (I think it is nerve gas) which has a very simple
> structure. Pure Ni is not harmful in small quantities, but obviously this
> organometallic comparison is. On the other hand, the organometallic
> compounds we ingest daily within vitamin tablets (you have to get Fe in some
> form your body can absorb) are obviously safe up to the point of liver
> poisoning (i.e., overdosing).
>
> Because of my newness to this forum, I am assuming ITRI has the task of
> leading (pun intended) the no-lead development in the PWB industry. I
> question it's importance. I even question it's objectivity (because that's
> what I always do in my work). But I have no doubt they are trying to
> evaluate solders without excess craziness as you suggest...
>
> And yes, if the medical community said 5 g of Sn is ok in some form (tried
> on animals, etc.), I'd eat it without worry...with chocolate on top, of
> course!!!
>
> Carey
>
> -----Original Message-----
> From: Brian Ellis <[log in to unmask]>
> To: [log in to unmask] <[log in to unmask]>
> Date: Monday, November 08, 1999 6:54 AM
> Subject: Re: [LF] Long-term solutions
>
> >Kay
> >
> >Obviously, you have to protect tin, that is what you are paid for.
> >However, would you **willingly** ingest just 5 g of any tin compound,
> >organic or inorganic?
> >
> >I repeat, no-one knows what reactions may occur in a landfill, simply
> >because no-one knows what is in water that reaches tin. It MAY be
> >perfectly benign, it MAY not. Furthermore, on the average PCB, apart
> >from oxidised tin, there are a neat variety of organic acids readily
> >available to reduce it!
> >
> >Going back to the start of this thread: it is my honest belief, ITRI
> >notwithstanding, that the presence of all anthropo-sourced metals,
> >beyond trace quantities, is undesirable in the environment. Sooner or
> >later, as more knowledge is gained, they will probably all be restricted
> >therefore they must be recycled to the maximum, tin and lead both. If
> >they are recycled, why ban them?
> >
> >Of course, I understand that the ITRI would prefer otherwise a) because
> >they receive their funding from tin production and b) because they would
> >prefer that solder contains 95%+ Sn, rather than 63%. I have no vested
> >interest in what I say, other than hoping electronics production may
> >continue as economically and as easily as possible.
> >
> >Best regards
> >
> >Brian
> >
> >Kay Nimmo wrote:
> >>
> >> Dear Brian
> >>
> >> I would just like to clear up some of the points you make on toxicity of
> tin. It is inaccurate to say that many tin compounds are toxic as
> distinction should always be made between organo-tin compounds and all other
> forms of tin. It is also inaccurate to generalise and claim all organotins
> are toxic. The toxicity is not specifically related to the tin, but to the
> nature and number of the organo- groups attached. See the paragraph below.
> >>
> >> As far as the comment on cans is concerned the lacquer coating is in fact
> there to prevent corrosion. In some cases a lacquer coating is deliberately
> not used in order for the tin to dissolve to a small extent in the acid food
> juice and stabilise colour and (apparently) taste. Take a look at your cans
> of tomatoes/beans etc and you will find that they are unlacquered, or only
> partially lacquered.
> >>
> >> The effect of distribution of tin metal in the environment has been well
> examined. In particular, the US Fish and Wildlife service made an extensive
> study on tin toxicity during approval of tin as lead-free shot. Data on the
> behaviour of tin in soils, water, wildlife, livestock and man was examined
> with tin succesfully passing this stage of the approval process.
> >>
> >> Kay
> >> ITRI
> >>
> >> Organotins: toxicity is related to the precise nature of the
> organo-moiety. Essentially, there are four basic types: mono- (with one
> organic group attached to the tin), di- (with two), tri- (three) and tetra-
> (four). As a generalisation, toxicity is greater for tetra- and tri- types
> than for di-, which in turn is greater than for mono-. However, within each
> type, it is the nature of the organo- groups attached to the tin that is
> important. With regard to mammalian toxicity, methyl- and ethyl- groups
> generally give the highest toxicity, whereas larger alkyl groups (e.g
> butyl-, octyl-) are less toxic to mammals, but are often more toxic to other
> species. For example, tributyltin compounds (e.g. TBTO) are particularly
> toxic to marine organisms, and are therefore used in antifouling paints to
> prevent barnacle growth on boat hulls. This is the application that TBTO was
> developed for. However, it is important to note that most of the di- and
> mono- organotin compounds used commerci!
> >!
> >!
> >ally
> >> (e.g. in PVC stabilisers, catalysts, tin oxide film precursors) are of
> low toxicity, and some are approved for food contact applications (as in PVC
> packaging). The main message is that it is wrong to generalise and say that
> all organotins (or, indeed, all tin compounds) are toxic.
> >>
> >> -----Original Message-----
> >> From: Brian Ellis [SMTP:[log in to unmask]]
> >> Sent: 05 November 1999 10:35
> >> To: [log in to unmask]
> >> Subject: Re: [LF] Long-term solutions
> >>
> >> I agree, but tin is also a severe issue which has not been sufficiently
> >> addressed. Many tin compounds are toxic (some organotin compounds are
> >> used as wood preservatives, fungicides, algicides etc.). Who knows what
> >> reactions may occur in a landfill? Anyway, tin is (or at least was) not
> >> federally regulated in waste water in the USA, although I believe some
> >> States may cap it at 5 - 10 ppm. However, in Europe, the levels are set,
> >> mostly at 1 - 5 ppm (copper at 0,5 - 2 ppm in many countries as a
> >> comparison). I won't discuss Malaysia's limit at 0,1 ppm, because this
> >> is a special case. Anyway, tin is considered about half as toxic as
> >> copper, so don't consider it as being exempt from all future regulation.
> >> Note that many tin-plate cans for acid foods are now polymer-coated as
> >> additional protection against the ingestion of tin salts.
> >>
> >> I think the crux of the matter is that ALL metals can be shown to be
> >> toxic in some form or another. Lead is just a technocrat's buzz-word and
> >> should not be treated differently from any other metal. When these guys
> >> cotton on to these facts, all metals will be banned, as will also
> >> bromo-bisphenols used for fire-retarding PCB laminates. There is only
> >> one logical solution: obligatory recycling of all metals. The sooner
> >> this fact is realised, the better: then we can get on with our business
> >> of soldering boards with tin/lead solders to our heart's content. AND I
> >> say this as one much and actively concerned with the protection of our
> >> environment.
> >>
> >> Brian
> >>
> >> "Bernier, Dennis" wrote:
> >> >
> >> > Though I am not an advocate of rapid changeover to lead-free solder
> alloys
> >> > without more reliability testing, I can see the lead-free alloys might
> be a
> >> > future environmental problem. However, the amount of silver and copper
> >> > combined in the solder will only be about 10% of the amount of lead in
> >> > Sn63Pb37 solder alloy used now. This will be a very small amount of
> metal
> >> > contamination due to the solder in the electronic product. It seems
> then
> >> > the copper may become the issue because there will be 20-50 times as
> much
> >> > copper in the assembly than silver.
> >> >
> >> > -----Original Message-----
> >> > From: Carol Handwerker [mailto:[log in to unmask]]
> >> > Sent: Wednesday, November 03, 1999 5:56 AM
> >> > To: [log in to unmask]
> >> > Subject: Re: [LF] Long-term solutions
> >> >
> >> > In the Assembly Processing group working on the Lead-Free Solder
> Roadmap at
> >> > the IPC meeting, the highest priority item from the group was to ensure
> >> > that the new alloys are viable in the long term from a toxicology and
> >> > environmental life cycle point of view. Having to change alloys again
> in
> >> > three years would be a waste of resources if we can formulate a proper
> >> > solution now.
> >> >
> >> > At 07:06 PM 11/02/1999 -0800, you wrote:
> >> > >All,
> >> > >
> >> > >As I read the debates ongoing, it strikes me that there are 2 major
> focus
> >> > >areas right now:
> >> > >
> >> > >1) Technical solutions to Pb-free solders
> >> > >2) Is the decision environmentally correct?
> >> > >
> >> > >Are we missing a 3rd item?
> >> > >
> >> > >Regardless of what solder we end up with, how does the industry
> position a
> >> > >long term, environmentally sound policy that will forestall future
> green
> >> > >initiatives from causing such upsets?
> >> > >
> >> > >The history of Pb is rife with abuses -- Workers not following safe
> >> > >practices, employers not requiring or implementing safe practices,
> emission
> >> > >controls not being in place on smelters, .... This is in addition to
> Pb
> >> > >being used without a full understanding of the toxicology and exposure
> >> > risks
> >> > >(Paint, gasoline, plumbing The point is, past uses (and abuses) and
> >> > >handling of Pb has created the situation we are in now.
> >> > >
> >> > >I have not seen/heard any discussion on establishing practices and
> >> > protocols
> >> > >that will foster responsible use of any solder -- Both safe working
> >> > >practices on the production end, and End of Life management. Should
> this be
> >> > >part of the overall strategy, or a recommended best known method? How
> does
> >> > >this link into product takeback requirements that are gaining
> popularity in
> >> > >the EU and Japan?
> >> > >
> >> > >Regards,
> >> > >Paul Wermer
> >> > >(Whose opinions are his own and do not necessarily reflect those of
> his
> >> > >employer)
> >> > >
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> >> > >Please visit IPC's Center for Lead-Free Electronics Assembly
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> >> > **************************************
> >> > Carol A. Handwerker
> >> > Chief, Metallurgy Division
> >> > NIST
> >> > 100 Bureau Drive Stop 8550
> >> > Gaithersburg MD 20899-8550
> >> > Office:(301) 975-6158
> >> > Fax:(301) 975-4553
> >> > e-mail:[log in to unmask]
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> >> > Electronic
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> >> > Please visit IPC's Center for Lead-Free Electronics Assembly
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> >> > Please visit IPC's Center for Lead-Free Electronics Assembly
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> Electronic
> >> Assemblies.
> >> Please visit IPC's Center for Lead-Free Electronics Assembly
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> >> Please visit IPC's Center for Lead-Free Electronics Assembly
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> >Please visit IPC's Center for Lead-Free Electronics Assembly
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> 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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(http://www.leadfree.org ) for additional information.
For technical support contact Gayatri Sardeshpande [log in to unmask] or 847-790-5365.
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