-----Original Message-----
From: David Whalley <[log in to unmask]
To: Circuit Connect <[log in to unmask]
Cc: TechNet E-Mail Forum. <[log in to unmask]
Date: Thursday, February 11, 1999 4:39 AM
Subject: Re: 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: 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. 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.

 Lazzara: No one can (or should) argue against recycling, but our social
 evolution in this regard is historically constrained by finance until
driven to
 change by legislation. Environmental legislation isn't always the best
 medicine, which is why in the US our Environmental Protection Agency
 has sponsored their Design For The Environment program, a forum that
 encourages industry and academia to collaborate for practical means
 to achieve specific improvements in waste generation (as opposed to
 waste management) and a pursuit in the elimination of materials the EPA
 identifies as hazardous. In the case of Lead, our EPA isn't satisfied with
 recycling because the toxic potential of lead isn't a fact that only
resides in
 landfills. An example of this ammunition: Few bullets end-up in landfills
 (although some might be buried at gravesites), yet there is great interest
 in having lead slugs changed to some other metal. Seems ironic, eh?, that
 society finds the need develop a less toxic lethal projectile. Well, for
more
 information about wide-ranging conversions from lead  -  from wheel
 weights to buckshot  -  visit http://www.itri.co.uk/index.htm (although
I've
 not yet found a CD by Bismuth Zepplin, I have noticed that many subjects
 for lead conversion aren't in todays landfills).

 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.

 Lazzara: I'll yield to your numbers' being true - but only for the moment.
 Nevermind my poor geology grades; I yield rather because your's is a
 snapshot statement about today's cost based on today's technology and
 today's market demand. Things change. Aluminum was once the most
 expensive metal on Earth, such that Faberge' crafted jewelery for the
 Romanov's with the substance. Demand and technology dropped price.
 I remember when PCB's introduced photo-imaged solder mask: Initial cost
 went up briefly until market demand and technology drove it down. A metal
 currently in transition is gold: Used to be a premium feature to PCB's but
 today it's sold by many suppliers as cheaply as lead. If gold can be sold
as
 cheaply as lead - well, what of bisbuth?

 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.

 Lazzara: Agreed.

 Whalley: There are also issues regarding the reliability of the alternative
 alloys.

 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: As far as I am aware no cost/benefit analysis has been undertaken
to
 justify a ban.

 Lazzara: As far as I am aware no cost/benefit analysis has been undertaken
 to justify the immediate pursuit of electronics assemblies with 100%
 reuseable content.

 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 opposite: They'll regard the factual evidence but effect NO
hange  -
 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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