Robin,

There may be a lot of technically plausible reasons why leaching of lead from
scrapped electronics in landfill does not by itself provide sufficient
grounds for eliminating lead from solder.    However, I feel that there is more to
the case for lead-free solder than simply that it is too late to stop the
consequences of some misguided European legislation.

I believe that there are two more general grounds that might be considered
justification for the move to lead-free.     An underlying premise is that lead
is indeed as dangerous to health and well being as is claimed by the
toxicologists.   The key point on lead toxicology seems to be that there is no safe
lower limit.   It is always the case of less is better.

The first is that, given that lead is a toxic material, it seems unwise to
continue to use it in an application which virtually ensures that it will be
scattered widely around the world.    Electronic circuitry is becoming
ubiquitous.    Even many of the very poor of this world have a radio and the middle
class, whose numbers are growing rapidly around the world, typically own 5 - 50
items which contain some sort of electronics.  And apart from private ownership
electronics are being scattered around the earth in communication, control and
monitoring equipment.   All of this electronics is eventually discarded and
may not necessarily end up in a recycling program or in managed landfill.   It
is as if someone were firing a shot gun  from space scattering tiny pellets of
lead nearly everywhere.    The fact that there is already a lot of lead
scattered around the earth as a result of the use of lead in paint, gasoline, car
batteries etc does not necessarily mean that it does not matter whether more is
scattered.   Lead has been largely eliminated from paint and gasoline and car
batteries are largely recycled.   It may be argued that there are technical
grounds for believing that those tiny pellets of lead are just going to lie
there, largely inert with none of the lead finding its way into the water supply
or food chain.   However, is it worth taking a risk when it is avoidable?

The second is occupational health and safety.   In this forum the point has
been made recently that at normal soldering temperatures the vapour pressure of
lead is not high enough for its fumes to create a significant problem.
However, it is my personal experience that if you are exposed to lead-containing
solder it is likely that your blood lead level will increase.   Blood lead
levels in most industrialised countries might already be elevated because there
is still quite a lot of lead from other sources about but that does not
necessarily mean that a further increase is of no consequence.   In electronics
assembly the greatest risk is for people working with processes involving pots of
molten solder, not because of lead vapour but because of the fine lead oxide
dust that is inevitably generated.    For those working with solder paste there
is always a small risk of ingesting the fine particles of solder powder on
which this product is based as residues of paste dry out and disintegrate.
Even for those handling solder wire, the lead oxide on the surface rubs off onto
the fingers and can find its way into the body by ingestion or, more
dangerously if the worker is smoker, by inhalation.   Of course precautions are
normally taken to ensure that blood lead levels of people working with solder stay
below the legislated limit.    Masks are worn when skimming dross off a solder
bath.  Strict hand washing procedures are followed before eating or smoking
and for people with the greatest risk of exposure there are periodic checks of
blood lead.    However, there can be no guarantee that such precautions are
always followed perfectly so the risk remains.   As contributors to this forum
have pointed out recently there are other health risks associated with
soldering, e.g flux fumes, but that does not necessarily mean that it is not worthwhile
eliminating this lead risk from the work environment.

It is true that the effects of the foregoing are small and so the question
remains as to whether they justify causing such great inconvenience to the
electronics industry.

Some years ago there was concern that a change to lead-free solder was not
technically possible.    There are certainly some challenges in making the
change but it does seem that it is technically possible.    There are already
hundreds of millions of printed board assemblies in service that have been made
with lead-free solder over the past five years.   The question of reliability
will remain at least partly unanswered until lead-free solders have been in
service as long as tin-lead solder has been but so far no problems have emerged
that seem to be beyond a technical solution.

Is the change to lead-free justified?

Since I am associated with a solder maker who might be considered to benefit
from a change to lead-free I cannot make that call.   All that solder makers
can ethically do is offer assistance to customers who find themselves obliged
to make the change to lead-free.

As a final comment, from my personal experience with Japanese I would say
that it would be unfair to suggest that their leadership in the change to
lead-free solder has been motivated by some devious commercial strategy.    Living as
they do on a small crowded island the Japanese are very conscious of
environmental issues.   And because of the Minamata disaster (thousands of people
suffering from severe mercury poisoning as a result of industrial pollution) they
have been acutely sensitised to the potential dangers of toxic metals in the
environment.    Perhaps the Japanese should be given the benefit of the doubt
that they are motivated by a genuine concern for the environment.

Keith Sweatman
Nihon Superior Co., Ltd.

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