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Re: lead free solder again


Hello Klaus,

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I have just finished another design and several parts were only
available in non-lead. We used regular lead solder, no problem.

--
Regards, Joerg

http://www.analogconsultants.com

Re: lead free solder again



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Yet....

The picture linked by the OP specifically shows whiskers growing on the tin
plated leads of a crystal in the area which had not been Sn/Pb solder
dipped.

--

Re: lead free solder again



nospam wrote:
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Found another reference, maybe this will help:

http://nepp.nasa.gov/whisker/background/index.htm

"What are Tin Whiskers?
Tin whiskers are electrically conductive, crystalline structures of tin
that sometimes grow from surfaces where tin (especially electroplated
tin) is used as a final finish."

Michael


Re: lead free solder again



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Yes, it's a concern for all tin plated surfaces. Sometimes you can get
other plating but typically only on high-end parts. Ultimetaly time will
tell. If this RoHS and WEEE stuff turns out to be a major blunder, and
chances are that it does, we'll probably see a reversal in
manufacturer's reactions.  To some extent we are already seeing that,
not in parts but in shipping policies. Don't know which one it was but I
have seen in the terms of one supplier that they simply will not ship
certain merchandise to Europe anymore.

--
Regards, Joerg

http://www.analogconsultants.com

Re: lead free solder again




Klaus Bahner wrote:

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That's wholly wrong. I was only reading recently about studies on whisker growth
on tin plated component leads.

I think it's accelerated by both high temperature and humidity btw.

Graham


Re: lead free solder again


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growth
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Ok, I should have been more precise. Even if there are only lead free
parts available you are still able to process them in a non-lead-free
process, which means you can easily coat your parts with a lead/tin
alloy. Comes automatically when you reflow SMD components with lead/tin
alloy, leaded parts may require special handling, if you mount them with
   largely exposed leads - but standoffs might be anyway a good idea in
such a situation. The popular picture of the tin whisker on the crystal
lead shows a crystal with a rather unintelligent mounting position
anyway. Avoiding mechanical stress, i.e. bending, shouldn't be a big
deal if you adapt your production to a lead free process.

Besides that I just don't think it's appropiate to call RoHS for the
doomsday of all electronics. So far, the incidents on NASA's popular tin
whisker site seem rather exotic to me (a satellite for example is
working under ultra high vacuum, extreme temperature and high radiation
conditions). I don't know whether RoHS will be a more complex problem
than adapting to other production issues. So far I think chances are
rather high that you can control it in the same way as other production
issues. (How many failures of end products were caused because
production plants didn't stick to the correct soldering temperature
profile or didn't bake components correctly?)


Klaus



Re: lead free solder again


On Wed, 12 Jul 2006 12:01:39 +0200, Klaus Bahner

snip.


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It's not "so far" at all. Have you not heard of the "Swatch" issue?

But, anyway,  the much bigger question is: what's the point of it all?
Where is the proof that lead leaches out of consumer electronic goods
in landfills and causes the alleged problem?

And why does the world need items made with a 37 Deg higher temp. That
energy has to come from somewhere. It may be a minor increase in the
overall energy account, but once again, where is the proof that lead
in solder is a problem?

And while I'm happy for the Euro-crats to take credit (I'm sure they
will) if it all works out fine, I'd also demand that they carry the
can if it does not. Who are they, and what are their personal assets?
Swatches' lawyers might be after them soon enough.

Barry Lennox

Re: lead free solder again


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In many places you don't even have landfills. The rubbish is
partly recycled and the rest is burned. The question is,
where does all the lead end up?

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That 37 degrees is a silly argument. The total amount of energy
needed to solder a board is peanuts, even if needed to be soldered
at +100 degrees.

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Time will tell.


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



Re: lead free solder again




Frank Bemelman wrote:

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It doesn't tend to get burnt in Europe which is where the legislation currently
applies. So the point is moot.

In any case, waste is dealt with under WEEE.


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That's not what the board stuffers say.


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Oh it will for sure.

Graham


Re: lead free solder again



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Yeah right - Measuring one of our ovens (max power draw is 100A at 208V 3
phase) it went from 12 to 15 kW when warm with a reasonable board load to
about 17 to 20 kw draw with a lead free profile, with about half the
productivity, maybe worse since we tend to run  the oven slower then we need
to with leaded boards. Nitrogen may also be needed in some cases, which
means that at least 2 times as much nitrogen would be needed for the same
amount of product processed.



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Re: lead free solder again


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Sure did I hear about it. But I was not able to read the original Swatch
report. Anyone knows where to find it? All I heard about it, were second
hand stories, rather confusing. Allegedely Swatch did use SnCu solder,
although SnCuAg seems to be the industry standard elsewhere. Maybe
Swatch just chose the wrong solder? Furthermore I heard that the Swatch
reports talks about tensile stresses as main reason for whisker growth -
which would be contradictory to the research literature. It is agreed on
that compressive stress is one of the main driving forces for whisker
growth. So not having enough information, the "Swatch" issue rises more
questions than answers. Sure Swatch apparently has a problem with lead
free production, but I don't think the swatch issue is sufficient to
conclude, that everyone and all electronics manufacturer will face the
same problems.

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Don't know for sure, just guessing. First of all, most of the consumer
electronics waste in the EU ends in a incinerator. Lead and the other
banned RoHS substances are a problem here.

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I don't see anything wrong with getting rid of unhealthy substances.
There might be more promissing areas than lead in solder, but this
doesn't make it wrong to attack lead. Certainly, industry will not take
action on its own. So some external force must become active.

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Since when can you sue a democratic elected representative? They just
passed a bill we may not like, they didn't commit a crime!

Klaus

Re: lead free solder again




Klaus Bahner wrote:

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You know how to use Google ?
http://www.google.com/search?client=opera&rls=en&q=swatch+lead-free&sourceid=opera&ie=utf-8&oe=utf-8

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Not so. The silver containing alloys are considerably more expensive.

Graham



Re: lead free solder again



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Don't you really expect me to answer that question?

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http://www.google.com/search?client=opera&rls=en&q=swatch+lead-free&sourceid=opera&ie=utf-8&oe=utf-8

So what, just lots of second hand information.

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Trying to save a few cents at the wrong place?

Klaus


Re: lead free solder again




Klaus Bahner wrote:

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http://www.google.com/search?client=opera&rls=en&q=swatch+lead-free&sourceid=opera&ie=utf-8&oe=utf-8
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If you follow it up you'll probably get to it. I know I found plenty of detail
last time I looked.


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The bulk of the info I've seen relates to SnCu. It's definitely the one being
most used.

Graham


Re: lead free solder again



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Perhaps because that gives the most problems.

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Perhaps the one being most mentioned?

In 2002 already 5-10% of consumer products
used lead free solder.

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





Re: lead free solder again


Hello Klaus,

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It doesn't? Eurocrats have an uncanny tendency to dump out the kid with
the bath water.

Oh, another idea for them: To curb pollution they could mandate that the
sale of car tires be prohibited.

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That's exactly the problem. On the contrary, even if voters (hopefully)
kick them out they can still be assured that the same voters pay them a
fat retirement benefit.

--
Regards, Joerg

http://www.analogconsultants.com

Re: lead free solder again




Klaus Bahner wrote:

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growth
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You are *joking* ! ??


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No it doesn't at all !


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And how many components wil faill prematurely due to the higher baking temp ?
This is
frankly relatively unknown territory.

Early results show degraded product reliability. Largely due to the poorer joint
that
lead-free soldering produces.

Not everyone's using aerospace parts btw !

Graham


Re: lead free solder again


On Tue, 11 Jul 2006 13:03:21 +0200, Klaus Bahner

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 This is SO absolutely wrong.

Re: lead free solder again


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Didn't know that lead was added not until the late 40's.

But if you spray finished boards with some kind of coating,
would that not prevent the growth of whiskers?

Anyway, I don't hear much complaining from large companies
so it might not be such a big deal after all. Time will
tell, of course.

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




Re: lead free solder again




Frank Bemelman wrote:

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You want to physically restrain the tin ? It's some kind of crystal growth so I
doubt it'll be bothered by a coating. In nay case what you're suggesting is
simply another band-aid on a truly bad idea.

There's plenty more problems anyway such as fatigue of the solder joint.


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Haven't heard about Swatch ?

I'm sure there'll be screams of anguish eventually when the full implications
come to light.


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Yes it will.

Graham


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