-----Original Message-----
From: David Whalley <[log in to unmask]>
To: [log in to unmask] <[log in to unmask]>
Date: Friday, January 29, 1999 10:59 AM
Subject: Re: [TN] Removal of Lead

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: 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: 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: 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: 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: ...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).

And THAT brings us back to our beginning!

Bob Lazzara
Circuit Connect Tech Support
Georgia Service Bureau

TEL: 800.560.9457  FAX: 888.453.0520  BBS: 603.889.5385
alternate eMail: [log in to unmask]

*In the U.K., the ITRI is the International Tin Research Institute. They can
be reached electronically at:
http://www.aslib.co.uk/aip/subs/itri.html

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