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Re: lead free solder again



Joerg wrote:
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  Hi Joerg,
  Richard has it half-right: I meant both a) a larger quantity of fuel
must be burned for the same motive result, nullifying the emissions
advantage, and also b) a fuel of higher toxicity results, due to the
MTBE.  Gasoline was never very good to drink, but MTBE made it
considerably worse, and a lot harder to get rid of.

  Best,
  James


Re: lead free solder again


Hello James,

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True, when the gasoline isn't combusted in an engine but leaks into the
ground then it certainly is more toxic. Gas stations are one concern but
I guess nobody in politics has thought about all the fuel that spills
while refilling lawn mowers and generators. Most people I have seen
doing that did not use funnels.

--
Regards, Joerg

http://www.analogconsultants.com

Re: lead free solder again



Joerg wrote:
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  Gasoline stations were the biggest offenders.  Eventually those
underground tanks leak.  It's very hard to notice a leak in an
underground tank that large, whose contents are constantly being turned
over, so quite a bit of gasoline can escape over time before being
detected.  My former outfit got some nibbles on solving that
leak-detection problem (though we never landed the business).

  Once in the ground, a "plume" of contamination spreads from the
point-source, poisoning the soil, and reaching groundwater deep in the
earth some time later.  Sometimes a lot later.  We had a big local
to-do some years back after discovering contamination in the ground
water, which was traced to a minor leaks at couple of gas stations.
Other stations were then examined, and *most* of them leaked.
One-by-one, the stations have all closed down, exhumed their tanks, and
put in new ones, but the MTBE is in the ground to stay; we'll have to
live with it.

  Best regards,
  James Arthur


Re: lead free solder again


Hello James,

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In Germany that problem has been solved since many decades. By law
in-ground oil tanks for heating oil, whether residential or commercial,
must be double-walled. There is a test liquid between inner and outer
wall. When either wall is compromised the level of this fluid begins to
drop and a really loud alarm sounds, two red lights flash etc. The
disable-switch of this unit carries a tamper seal and IIRC the inspector
who checks the furnace every year is supposed to test the unit and look
for signs of tampering.

--
Regards, Joerg

http://www.analogconsultants.com

Re: lead free solder again



Joerg wrote:
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  Very sensible, and elegant.  The guys who came to us wanted an
electronic solution, to track a tank's in-and-outflow with infinite,
impractical precision (we were to provide the telemetry), but they
failed; electronics isn't always the answer.

  Regards,
  James Arthur


Re: lead free solder again




snipped-for-privacy@yahoo.com wrote:

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The concept was the problem in this case.

Graham


Re: lead free solder again



Eeyore wrote:
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  Indeed.  "If a problem has no solution, it may not be a problem, but
a fact -- not to be solved, but coped with..."  Shimon Peres

  Best,
  James Arthur


Re: lead free solder again


Hello James,

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A totalizer? That's ridiculous, that idea probably came from a bureaucrat.

It seems like the usual "not invented here" syndrome. Why not just copy
the German system if it works? But NIH syndromes can be found over there
as well. Instead of copying California's proven Fastrak toll system they
absolutely had to invent their own, causing various initial blunders.

The leak detectors in Germany are dirt simple, I'll try to recall it
from my gray cells: A small pipe from the intermediate cavity into the
house connects to a little reservoir the size of a two-gallon paint
bucket. Inside is a float switch and that connects to the flashing
lights and siren unit. No electronics, plain and simple. The reservoir
has a side glass so the inspector merely has to look, no need to gauge
with a dip stick. The reservoir's mounting height is critical and must
be matched to the buried tank, typically by using a water level. I think
they also have units for tankside mounting but ours was inside the
house. BTW, they also have sensors (now mandatory AFAIR) that connect to
the tanker truck upon delivery. This sensor shuts off the truck's pump
when a certain fill level is exceeded, to avoid topping off spills.

--
Regards, Joerg

http://www.analogconsultants.com

Re: lead free solder again



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Close but no cigar.  MTBE provided the required oxygenation without the
performance penalty of ethanol.  That MTBE was the most toxic gasoline
additive to date (at usage levels) was even acknowleged.  What was swept
under the rug early on was MTBE persistence as an environmental pollutant
and the strength of its carcinogenic properties.
--
JosephKK
Gegen dummheit kampfen die Gotter Selbst, vergebens.  
We've slightly trimmed the long signature. Click to see the full one.
Re: lead free solder again



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   It would be helpful to disclose some of that information..

Re: lead free solder again



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Contact bonding has been used in a variety of places for years. Have a
look at:
http://ap.pennnet.com/Articles/Article_Display.cfm?Section=Archives&Subsection=Display&ARTICLE_ID82%206&KEYWORD=lead-free
For an overview of the advantages/disadvantages.
The IEEE site, also has a paper on this technology.
I have used it as an assembly process on a couple systems. It's biggest
weakness came at higher power, where the extra resistance, both
electrical, and thermal, does become a problem. Personally, I think the
chemicals involved in the epoxies are much nastier to handle than lead
solders, but of course, once the resin sets, they result is very inert
indeed.

Best Wishes



Re: lead free solder again


Hello Roger,

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http://ap.pennnet.com/Articles/Article_Display.cfm?Section=Archives&Subsection=Display&ARTICLE_ID82%206&KEYWORD=lead-free
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Bonding is one very viable alternative. Besides thermal and electrical
resistance an issue that frequently crops up especially in highly
regulated areas such as here in California is fumes. Once cured, most
adhesives are ok. But while the dispenser robot is going the stench can
be quite nasty and you'd have to scrub all the toxins out of the exhaust
air.

--
Regards, Joerg

http://www.analogconsultants.com

Re: lead free solder again


Hello Robert,

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Sorry, but that isn't possible because it is a tightly guarded trade
secret. Just this much I can say: We have to stop thinking just about
solder to do connections, sometimes it isn't the right stuff. Especially
in very dense situations where whiskers do present a problem. Head in
the sand or "it'll all be ok because the legislators said so" like some
people seem to prefer is not the solution.

--
Regards, Joerg

http://www.analogconsultants.com

Re: lead free solder again




Frank Bemelman wrote:

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Really ?

Before he vanished John Woodgate reported about the increasing failure rates of
TVs made with lead free processes !

And they were 'complaining' in an industry mag.

Graham


Re: lead free solder again



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   I repeat: coatings (of any kind) are *NOT* reliable!
   There is *NO* known method to "cure" tin whiskers - other than not
using tin!

Re: lead free solder again




ian field wrote:

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Well said, that man !

Graham



Re: lead free solder again


Hello Frank,

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Have you dealt with TSSOP packages or even smaller ones?

The real problem will be when a male whisker pokes through and see a
stunning female whisker ... :-)

--
Regards, Joerg

http://www.analogconsultants.com

Re: lead free solder again


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No, TQFP is the smallest I have used.

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Oops didn't think about that. Since I thought they were
actually hermafrodites, I suppose this is an advantage ;)

--
Thanks, Frank.
(remove 'q' and '.invalid' when replying by email)







Re: lead free solder again




Frank Bemelman wrote:

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I'm just pointing out that's its having negative environmental effects which is
somewhat ironic.

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Of course it's a hassle esp for smaller companies who are supposed to maintain
utterly unrealistic quantities of records ro prove their product is lead-free
for one thing and the relative uncertainties about the soldering process which
hits smaller companies without vast engineering departments harder.


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Well, we're not all in the same boat. Smaller companies will be worst hit.


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It has no surface tension to help wetting for one thing.


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I just read btw that lead-free is actually meant to make waste recycling easier
and is supposed to be the main motivation for RoHS..

I frankly can't see what there is in modern eelctronics that can be usefully
recycled once it's soldered to a pcb anyway. By far the best thing to do is
indeed dump it.

Graham


Re: lead free solder again


[....]
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On the other hand, the point of a tin whisker may be the sharpest thing in
the universe.  Depending on how the crystal is growing the point may be
one atom thick.

[...]
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So why not widen it to include all electronics?  Can you find a dividing
line?

--
--
snipped-for-privacy@rahul.net   forging knowledge


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