Hi Bob,

I am pleased to see (and contribute to) some serious debate on this
issue. Here are my responses to your comments:


Whalley: The draft European WEEE legislation proposes prevention of
electronic equipment being consigned to landfill.

Lazzara: Presumably due to lead being a toxic substance.

Whalley: And because land fill is a waste of land and because burying
other hard won resources such as plastics, copper, tin, silver, etc is
probably not a very good idea.



Whalley: An additional ban on the use of lead solder therefore cannot be
justified for this reason. There are also existing technologies for the
recovery of the lead from the solder in obsolete electronic hardware.

Lazzara: Wait  -  Is this the logic where a pound of cure is better than an
ounce of prevention?

Whalley: No. It is the logic that as engineers we have a moral duty to
question policies that _may_ have net negative effect on society and the
environment. Untill someone shows me a proper cost/benefit analysis I will
continue to suspect a lead ban will not help the environment, either short
term or long term. Tin/lead solder can be readily dissolved in nitric acid
and the lead electrolytically recovered. I'm not a chemist, but recovery of
other solder materials will probably be much more difficult.



Whalley: All of the proposed replacements are significantly more expensive
than tin/lead.

Lazzara: According to a January 1997 report by the ITRI*, "Lead-Free
Solderable Coatings and Their Compatibility with Lead-Free Solders" (Kelly,
Ahluwahlia, Nimmo), the difference in cost between OSP, palladium, silver,
gold and tin alternatives were not significant. But that was 2-years ago.
Since that early 1997 report many North American shops offer soft gold
(in-volume) at no additional charge. Ditto OSP. And several companies now
offer non porous immersion tin below the cost of tin/lead HASL.

Whalley: OK, the board finishes may be cheaper, but what about the solder
alloy for assembly? If we remove lead we must replace it with something
else. Tin & bismuth are roughly 10 times more expensive, copper 3 times,
silver 100+ times. These costs can only go up if demand increases.



Whalley: Most also require a higher reflow temperature and hence greater
energy costs.

Lazzara: Not in all cases. I believe immersion tin tends to dissolve into
solution at lower temperatures than is necessary to render HASL coatings
liquid. But any slight elevation in temperature that might be required is
offset by the substantial thermal stress removed from the PCB by eliminating
HASL. Ironically, it is precisely the energy savings from eliminating HASL
that permits the alternative finishes to meet or go below the cost of HASL.

Whalley: Some studies have shown a lower superheat during reflow is possible
with some of the lead free solders, but some increase in reflow temperature
is almost certain to be required. The savings from avoiding HASL can be
gained whether the solder is lead free or not.



Whalley: There are also issues regarding the reliability of the alternative
alloys. As far as I am aware no cost/benefit analysis has been undertaken to
justify a ban.

Lazzara: Reliability has and continues to be a concern with Ni/Au
embrittlement, to such an extent that the ANSI-J-STD-001-B actually
prescribes the removal of all gold  -  from components and solderable
ands  -  prior to assembly. But the newer alternatives have done very well
in reliability testing and the reputations of their 1960's predecessors is
fading (e.g., "...growth rate of tin-copper intermetallic compounds on tin
coated copper is similar to that of Sn-40Pb coated copper, not greater as is
sometimes feared."*) Please do pursue a copy of the mentioned ITRI report; I
think you'll find it addresses the reliability issue objectively, and much
more data from many sources has since been generated concerning the
reliability of these coatings.

Whalley: Thankyou Werner for your support on this issue, and I agree that
generally that fatigue life won't be dramatically different, but I am also
worried that more catastrophic failures may occur in some types of assembly
- sometimes it is only the "softness" of tin/lead that keeps stress levels
acceptable and a much "harder" solder might result in for example component
fracture.



Whalley: ...but as usual the European Commission does not regard factual
evidence necessary before it drafts legislation.

Lazzara: I suspect the EC isn't unique in that mode. Yet many companies are
just the: They'll regard the factual evidence but effect NO change  -  which
in-part explains why we have such institutions as our Environmental
Protection Agency (EPA).

Whalley: No, the Commissioners aren't unique in this respect, but the European
Parliament usually manages to curb their wildest excesses!


David Whalley

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