Dear all,
Attacchment apparently are not distributed by the server at all, I found out from reactions on my posting of this morning. Therefore, I copied all text from the attached word document into this message. In my Lotus Notes environment it looks very good. I
hope that it will be readable in your own mail system too.
Best regards, Erik
The ECO-impact of metals applied in soldering of electronics
Introduction
Banning lead from soldered electronics has become a hot topic for quite some time already. However, to arrive at environmentally friendly alternatives, requires insight in the ECO-impact of the metals that can replace lead in solder alloys and in
solderable finishes.
In the framework of the BRITE/EURAM project IDEALS on lead-free soldering, a limited ECO-impact study has been performed for soldered electronics by environmental scientists of the PHILIPS CFT group on environmental aspects. In this posting, an attempt
is presented to clarify some points around the ECO-impact of the metals used for soldering. The ECO-impact of electronic products is not only determined by the waste stage, but rather by the total life cycle, from or- to-waste, craddle-to-grave,
ashes-to-ashes, dust-to-dust, including disposal and/or recycling (see e.i.: "Life Cycle Assessment (LCA) explained"; PRé Product Ecology Consultants, HTTP://www.pre.nl). This contribution is intended to give some feeling about the orders of magnitude of
the various stages and how these compare.
Discussion on Life Cycle Impact of soldered joints in electronic products
The lead-free solder alloy family at which the whole world arrives is the ternary eutectic composition SnAg3.8Cu0.7 with a melting point of 217C. It may be slightly modified to achieve specific properties such as fine grained solidification structures,
higher creep strength, low tendency to liquid cracking, and better wetting capability. To see how the lead-free solder composition compares to the total ECO-impact of the eutectic tin-lead composition, SnPb61.9 (or SnPb40 or SnPb37), is not easy to
answer; insufficient data is available for the waste stage of the metals to give accurate values, but at least an order of magnitude can be given for a couple of metals. This applies similarly to lead-free solderable component and board finishes. The
main ECO impact determining factors for these materials are:
· mining
· transport
· solder production process; component plating processes
· soldering process
· lifetime of the product
· waste stage (collection, disposal, recycling).
Each aspect is different such that direct comparison is impossible (like comparing apples with pears). Therefore, methodologies are in place to validate the various aspects and to arrive at the total ECO-impact of materials or products, the ECO indicator
value, expressed in ECO-points, numbers without dimension. (see i.e. "The Eco-indicator 95: a tool for designers"; PRé Product Ecology Consultants, HTTP://www.pre.nl; a methodology, relatively widely accepted in Europe.) It works as follows (see also
Appendix):
· First, the impact type is defined ( heavy metals, volatile organic compound, CO2 & SO2 emission, depletion of natural resources, etc. ).
· Then, it is determined which combination of environmental effects is caused by this impact, and to which degree.
· Following, the damage type of these effects is determined: human fatalities, health impairments of humans, and/or impairment of ECO-systems.
· The valuation is subjective and thus a matter of political discussion. As long as that is still going on, the valuation is taken unity for all three damage types.
· The final result is an ECO-indicator value in ECO-points (for materials per unit of mass). That has no dimension and can be directly compared with the ECO-indicator values of all other types of impacts.
To be able to do a total life cycle assessment, data of the impact in all factors and stages mentioned above should be available.
· For mining, the ECO-Impact 95 method database contains values. These are dated, of course, and incomplete, but do provide an insight in orders of magnitude.
· Unfortunately, waste stage data for many metals is missing to a large. Emission to air of mercury and lead have the same value of 92 points per kg and for heavy metals of which the data are not available, this value is often taken as a dummy.
(For comparison of different metals this does not bring very much, because it will make that ?everything equals everything?.)
ECO impact values of most metals used in soldering of electronics, respectively for mining, transport, and waste, are presented in Tables I, II and III, as far as available in the database at the time. The ECO-impact values for transport are negligibly
small compared to mining and waste. The ECO-impact during service life is negligible too.
A worst case scenario for the waste stage is disposal into landfill, followed by leaching out of maximum 1% of the metal into the soil water. For incineration the same worst case value can be applied. (Discussions in the forum have shown that this is an
aspect that still requires a lot of attention.)
At present, the contribution of SnPb component finishes to the Pb-content of SnPb40 soldered electronics is about 5 %; negligible in the order of magnitude comparison, but an important aspect when a change-over to lead-free is going to be made.
Table I: ECO-impact of mining of metals applied in soldering in electronics (ECO-points per kg)
Metal ECO-indicator value Metal ECO-indicator value (pts.kg)
Sn
Pb
Ag
Cu
Ni
Cd 0.0133
1.2
1.5
0.076
0.38
1.3 Zn
Au
Pd
Pt
Fe
Cr 0.65
100.1
375.3
563
0.011
0.053
Table II: typical ECO-indicator values of means of transport (milli-points per ton.km)
Means of transportation ECO-indicator value
(milli-points/kg)
airoplane
ship; freight
ship; container
railway
truck <3.5 tonnes
truck 40 tonnes 0.85
0.102
0.069
0.073
3.317
0.755
Table III: ECO-indicator values of emission of metals to (soil) water and to air (points per kg)
Metal Emission to water
(points/kg) Emission to air
(points/kg)
Sn
Pb
Sb
Bi
Ag
Cu
Ni
Cr
Cr-VI
Cd
Hg 92*
92
184
92*
92*
0.46
46
18.4
--
276
920 92*
92
92*
92*
92*
92*
4.05
--
404
4600
92
92*: no data available; the value for the heavy metals Pb and Hg, 92 pts/kg, has been taken as a dummy value. In doing this the outcome will be that everything equals everything.
Comparison of environmental impacts
There are some surprises in this data, as follows:
· The ECO-impact of mining of noble metals is huge; up to almost five orders of magnitude larger than tin and steel. (Think of what has been posted to the forum recently. Huge amounts of soil to be dragged around, enormous energy consumption and CO2 +
SO2 emissions, large lakes with residues such as cyanides, thyo-ureum and heavy metals, etceteras. Think of the recent environmental catastrophe in Rumania and the one a feew years ago in Spain/Portugal..
· Comparing lead with nickel we arrive at the following figures:
· Mining: Pb : Ni = 3 : 1
· Waste: Pb : Ni = 2 : 1
Pre-plated leadframes for semiconductor devices have a nickel plating with a thickness of 2-4 micrometers on the whole surface area. Further, about 0.1 micrometer of palladium often some gold are present on top of that. Compare this to 15 mass % of lead
in a 10 micrometer thick SnPb15 finish on the outer terminations only. That will show that the ECO-impact of Ni/Pd/(Au) pre-plated leadframes, based on these figures, is one to two orders of magnitude larger than that of SnPb15 plated terminations.
· As the ECO-impact of Ag, Sn, Bi, etc. is unknown, it is impossible to determine which lead-free alternatives for solder alloys and solderable finishes have the smallest environmental impact. (It may even come out that SnPb is the best, if recycled
properly.)
A recent publication in the conference ?Electronics Goes Green? Berlin ? Germany, 11-13 September 2000 supports these points: O. Deubzer, T. Suga, H. Griese, ?Ecological and Economical Effects of Lead-free Soldering?, p.51-57.
Eindhoven ? The Netherlands, 12-12-2000
Erik E. de Kluizenaar
Determination of ECO-impact value of materials according to the
ECO-impact 95 method
A number of substances are environmentally hostile. Below, the most important substances regarding ECO-impact and families of substances are listed.
IMPACT/SUBSTANCE
· CFC
· Pb; Cd; other metals
· Poly-Aromatic Hydrocarbons (PAH)
· Dust
· Volatile Organic Compounds (VOC)
· DDT
· CO2
· SO2
· NOx
· NH3
· P
Each substance causes certain effects, as listed below. Some contribute to more than one effect, others only to one.
EFFECT
· Ozone depletion
· Heavy metals
· Carcinogenics
· Summer smog
· Winter smog
· Pesticides
· Greenhouse effect; global warming
· Acidification
· Eutrophication
· Depletion of limited natural resources
The damage can be divided in impact on humans and impact on ECO-systems, as presented below.
DAMAGE
· Fatalities
· Health impairment
· ECO-system impairment
One can argue that one type of damage is worse than another. This, however, is a political discussion. As long as the outcome is pending, all damage types are considered to be of equal value.
SUBJECTIVE DAMAGE ASSESSMENT
· 1 : 1 : 1
The result of an inventory is an ECO-impact value in (dimensionless) ECO-points per unit of mass.
RESULT
· ECO-indicator value (ECO-points per unit of mass)
PS:
In the meantime the method has been upgraded to the '99 method. A lot more details has been added. However, the lack of data for the ECO-impact of emission of metals is still there.
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Erik E. de Kluizenaar
PHILIPS CFT - Electronic Packaging & Joining (EP&J)
Building SAQ-p, p/o box 218, 5600 MD Eindhoven - The Netherlands
Tel/Fax: (+31 40 27) 36679/36815; E:mail [log in to unmask]
PHILIPS homepage: http://www.philips.com; PHILIPS CFT homepage: http://www.cft.philips.com
Internal PHILIPS only: http://pww.cft.philips.com/cfteurope/electronics/elpajo/index.htm
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