Hello Everyone,
While several subscribers have commented on the Minneapolis summit,
I have not seen in these comments, nor in the vast majority of papers
presented, much in the way of comparitive analysis of environmental
impact of the LF alternatives. There seems to be two specific areas
which are not being addressed - relative environmental toxicity of the
LF alternative, and relative recycleability of the end-of-life (EOL)
LF product. Perhaps the FEAR factor of a lead ban is driving such
abbreviated evaluations, but market share is a powerful driver too.
1. Comparitive leaching
These shortcomings are surprising since the alleged reason for
developing LF electronics assemblies is mainly environmental, even
though no data exists which links any adverse enviromental impact from
lead to electronic solder or assemblies. The only adverse lead impact
on the environment that we heard was that from Katsuaki Suganuma of
Osaka University. He showed that 1996 and 1997 monitoring data from
over 2000 waste storage areas in Japan showed 0.3%, or roughly 6 sites
had lead levels in the groundwater (GW) of 1 ppb or more. There was no
linkage to waste electronic products presented. This data is
consistent with the 1991 data presented by Jeff Miller of the Lead
Industries Association (LIA) wherein two of 146 US municipal landfills
analyzed had GW contamination, and both were traced to industrial
waste disposal, a practice banned long ago in the US.
The immobility of lead in the GW should not be surprising given the
insoluble precipitates that lead forms with sulfates. One reported
study of ancient Roman lead smelters revealed an estimated one yard
movement in two thousand years! By comparison, we heard of the high
levels of leaching of both silver and antimony from Ed Smith of K-Tec.
Specifically, of the eight solder alloys tested, antimony and silver
leached from all forms with all leach tests. The only presenters that
I recall addressing the toxicity of leachate from LF alternatives were
Karl Seelig of AIM Solder and Ken Snowden of Nortel. Of interest is
AIM's TCLP results (which were not in the paper or on their website)
which did not show leaching above TCLP hazardous waste levels for
either silver or antimony.
2. Recycling solution
The response to the toxicity concerns of LF alternative solders was
that even LF electronic assemblies need to be recycled. While this is
true, it is more critical that they be recycled because of the higher
relative mobility of the leachate from say silver. The implementation
issues for recycling electronic products is underestimated in my
opinion, and in Alan Rae of Cookson's presentation. I don't think that
too many in the industry understand the enormity of the reclaim cycle
that he described (from consumer to collector to dismantler to refiner
to processer to fabricator and back to the consumer). In fact, isn't
this the key issue in the proposed rev 3 of the WEEE directive? (i.e.
who's going to pay to collect WEEE?)
For nearly 20 years, it has been illegal to dispose of industrial
waste that tests "positive" for TCLP characteristics such as lead, or
silver, and the other six RCRA metals. Hence, both PWB and PWA mfgrs
in the US have had to recycle these byproducts, as they are prohibited
from being landfilled (or incinerated) at non-TSD (treatment, storage
or disposal) facilities. These restrictions have not applied to
consumer wastes, but there's been successful consumer recycling
programs for used oil, newspapers, certain plastics, aluminum cans,
etc. No reason why one for consumer electronics couldn't be started.
3. Recycleability
A key area in selecting a LF alternative is whether the EOL
products can be recycled at the same or higher rate than the present
SnPb products area. What was quite surprising to hear from Ken
Snowden's presentation is that major copper smelters in both North
American and Europe will not take material with more than 20 ppm
bismuth in it! This could be a real show stopper for solders
containing Bi, unless shipping these EOL products to Japan is done, as
Japanese smelters reportedly do not have such restrictions.
Unpopulated PWBs are roughly 20% Cu and 1% Pb. We heard that PWAs
are about 3% Pb. Assuming that the components and added solder double
the weight of the PWB, the PWA would be about 10% Cu. The 3% Bi solder
that Panasonic developed would therfore, result in about 2500 ppm Bi
on the PWA. After EOL, where would these WEEEs w/Bi be recycled if the
major Cu smelters in N.America and Europe won't take them?
4. Other environmental issues
We heard one paper on the technical abilities of an immersion
silver finish on PWBs. However, PWB fabricators must meet an extremely
low discharge limit for silver. Typically 0.05 to 0.15 ppm, much, much
lower than lead and other PWB metals. Given the high aquatic toxicity
of silver, PWB shops will have to use extreme care to prevent wiping
out the biological activity of the sewer authority to which they
discharge.
The International Chamber of Commerce's (ICC) Business Charter for
Sustainable Development contains 16 principles. Based on what I heard
and read the the Minneapolis summit, I'm not sure that the following
have been addressed thoroughly with the LF presentations that I heard:
"6. Products and services
To develop and provide products or services that have no undue
environmental impact and are safe in their intended use, that are
efficient in their consumption of energy and natural resources, and
that can be recycled, reused, or disposed of safely."
"9. Research
To condust or support research on the environmental impacts of raw
materials, products, processes, emissions and wastes associated with
the enterprise and on the means of minimizing such adverse impacts."
"13. Transfer of technology
To contribute to the transfer of environmentally sound technology
and management methods throughout the industrial and public sectors."
To sum up my concern, the Assembly breakout group's #1 concern/
roadblock was as follows:
"Insure that the alloy of choice won't be banned in ten years"
Succintly stated. In my opinion, the LF development efforts have been
focused on the technical issues of melting point, solderability,
wetability, reliability, etc, which they need to, but they also need
to focus on the ICC principles stated above. From what I heard, many
of the technical issues have been addressed, but few of the
environmental impacts have been.
Nortel's SnCu solder holds promise if high temperature substrates,
HASL oils and components can be developed, as does Toshiba's SnZn
solder if application issues can be developed. I'm not comfortable
that solders containing silver, antimony and bismuth wont' be banned
in ten years if lead is banned now. Lee Wilmot
HADCO Corp
NOTE: These views are mine, and not necessarily those of my employer.
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