It is amazing the loops we go though. I remember being involved in whiskers
about 40 years ago. the information I got then is that tin wgiskers only
grow from pure tin, I cant now remember the level of alloying that is
necessary to suppress the growth. The problem I had tuened out to be a
"lead"tree growing electrochemically in the presence of, and inn contact
with, liquid water. However I used to have an unbelieveable photograph I too
of a silver whisker on some telemetry equipment, this was accelerated I
believe by the atmospher containing sulphur (sulfur to you) probably
outgassed from rubber based cable sheaths. Again I believe the whisker
growth is only from pure metal in this case plating. But even the thick gold
plating beloved of the military and seen on a lot of HP pcbs in the 70s
causes embrittlement of tin/lead soldered joints.

I have been using 99.25%tin/copper alloy recently and have been surprised by
the "look" of the handmade joints, quite "shiny" but I am guesing that is
not sufficient "foriegn" material to stop the whiskering, and any more would
increse the melting point. Thanks for the URL references they will make an
interesting read. (I have a large stock of tin/lead for my personal hobby
use) I wonder how much lead leeches off Cathedral roofs in areas of acid
rain like the big cities !!

Alan G3NYK
----- Original Message -----
From: SAIDJACK@aol.com
To: time-nuts@febo.com
Sent: Friday, September 25, 2009 12:38 AM
Subject: Re: [time-nuts] RoHS Solder

environmentally

to

Silver

https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts

I find that hard to believe.. the use of silver in photography is rapidly dropping.. I think it used to be about a third of the total market, and now it's something like 10%.

A bit of googling shows that there are something like 3300 million ounces not yet mined, but found.

A chart shows existing mines producing around 200 million oz/yr, so that's 15-16 years production.. not too far into the future, I admit.
The same chart showed a demand of about 800 million oz/yr (there's significant recycling of silver).

But, anyway, of that 200 million oz, how much is going into lead-free solder.  EPA says about 180 million pounds/yr of tin-lead solder. I think the usual formulations are 2% silver, so 3.6 million pounds/yr of silver (14.6 troy oz/lb, so 53 million oz/yr... a significant chunk, but only about 6-7% of the total world usage.. )

And those unmined reserves are based on whatever silver prices are now.. ($15-17/oz, I think)  If the demand increased significantly, it might spur exploration OR, more likely, the usage of lower grade ores. Unfortunately, silver is a mineral that concentrates (unlike, say, iron), so it's not like dropping the grade by a factor of 2 leads to an increased abundance of a similar factor.  However, even if the silver price doubles, it's a small part of the cost of a piece of electronics... sure, silicon is made from sand which is pretty common, but it's very expensive processing that sand to make functional dice and to put them in packages.

SAIDJACK@aol.com wrote:

It's even worse than it appears.

If you consider the danger of drinking water from lead  pipes, there
is clearly  some risk in disposing of lead in a  landfill.  Since it
accumulates in the body, the EPA sets the MCLG limit at zero:

http://www.epa.gov/safewater/contaminants/index.html

The maximum  contaminant level goal or MCLG means the  maximum level
of a contaminant in drinking water at which no known  or anticipated
adverse effect  on  the  health of persons  would  occur,  and which
allows an adequate margin of safety. Maximum contaminant level goals
are nonenforceable health goals.

http://ecfr.gpoaccess.gov/cgi/t/text/text-idx?c=ecfr&sid=c941f8ad5ebba0e8e95aae4dc8a070e2&rgn=div5&view=text&node=40:22.0.1.1.3&idno=40#40:22.0.1.1.3.5.16.4

However, every  year,  approximately  800,000  tons  of automotive
batteries enter the European Community market:

http://epa.gov/oswer/international/factsheets/200806_tl-eu-directive-batteries-accumulators.htm

A European directive sets a target for the recycling of at least 65%
by weight of lead-acid batteries by 26 September 2011:

http://europa.eu/legislation_summaries/environment/waste_management/l21202_en.htm

So each year, the remaining 0.35  *  800000  =  280,000  tons would
presumably end up in landfill somewhere.

It is  difficult to see how the amount used in electronics  can even
remotely compare with the amount involved in illegal disposal of car
batteries.

Mike

China have set up a pilot plant to extract Uraniun from coal fired power station ash. The concentration is the same as medium grade ore, but they don't have to mine it. If a US nuclear power station relased as much radiocative material as the average coal fired one it would be shut down!

Robert.

--- On Fri, 25/9/09, d.seiter@comcast.net d.seiter@comcast.net wrote:

Hello,

There is the same strange thing with mercury:
According to this article in Popular Mechanics, if you factor in the
higher energy usage of an incandescent bulb, because of the mercury that
is released from a coal fired power station, even if you crush the
CFL at EOL, the total value would be much less for the CFL!
(And of course, we all dispose of those nasty mercury containing CFLs
properly,
don't we?)

http://www.popularmechanics.com/blogs/home_journal_news/4217864.html

Greetings,
Pieter.

Years ago I had a friend in the Nuclear Powerplant business. The DOE or
AEC had this fiction of the "AEC Cow" used to set radiation limits.

They assumed a cow would spend 24/7/365 grazing against the fence of a
plant, and that a single kid would be drinking every drop of milk from
that cow.

In fact, the kid would die from heart disease brought on by Cholesterol of
many, many hundreds long before any radiation impact was seen.

Best,
-John

===============

That reminds me a shor story 'Survey Team' by Philip K. Dick :)

Regards,

Javier

d.seiter@comcast.net escribió:

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