Lead-Free Solder: Weird Behavior

[John Woodgate]

I read in sci.electronics.design that John Larkin
<jjSNIPlarkin@highTHISlandPLEASEtechnology.XXX> wrote (in
<48f041p5h5g263fukkisnl34kb33om4k2g@4ax.com&gt about 'Lead-Free Solder:
Weird Behavior', on Tue, 22 Mar 2005:

Some people solder with pure indium which (I think) has low vapor
pressure.

Second only to gallium, I think, for difference between melting and
boiling points:

Ga 29.8 and 2070 C In 156.6 and 2050 C

High boiling point implies low vapour pressure. Normally.
--
Regards, John Woodgate, OOO - Own Opinions Only.
There are two sides to every question, except
'What is a Moebius strip?'
http://www.jmwa.demon.co.uk Also see http://www.isce.org.uk

 

[Rich Grise]

On Tue, 22 Mar 2005 07:50:37 -0800, John Larkin wrote:

UHV is a huge nuisance. The people who do this tend to be unnaturally
patient. "Well, we may have a leak or we may have a fingerprint
somewhere. Let's pump it down for a week or so and see what happens."

Yeah, but that big tank of helium is fun at the company party!

Cheers!
Rich

 

[John Larkin]

On Tue, 22 Mar 2005 18:05:41 GMT, Rich Grise <richgrise@example.net>
wrote:

On Tue, 22 Mar 2005 07:50:37 -0800, John Larkin wrote:

UHV is a huge nuisance. The people who do this tend to be unnaturally
patient. "Well, we may have a leak or we may have a fingerprint
somewhere. Let's pump it down for a week or so and see what happens."

Yeah, but that big tank of helium is fun at the company party!

Second only to nitrous.

John

 

[Mark Jones]

Robert Baer wrote:

Daniel Haude wrote:

On Mon, 21 Mar 2005 21:36:07 GMT, Robert Baer <robertbaer@earthlink.net
wrote in Msg. <b7H%d.1254$H06.109@newsread3.news.pas.earthlink.net

Secondly: plumbers solder is not lead free, and usually uses ACID (!!);
there are numerous strong recommendations against use of plumbers solder.
And it is *not* considered fit for electronics use.



Actually what I used isn't really plumber's solder. I just called it that
because our workshop always uses it when they solder copper pipes, but it
is lead-free solder.


There are numerous *electronic* lead-free solders: * Sn 95.5, Ag 3.8, Cu
0.7 - MP 217C / 423 F; adopted by NEMI adn many high volume consumer OEMs




That's what I have here and what I wanted to use. After it showed those
weird effects I went back to my "old" Pb-free solder only to find that it
behaved the same.

--Daniel

That would indicate that the amount of copper in that is insufficent to make
it eutectic; that more copper is needed. Contact Kester for those technical
details. One would think that they would make eutectic (or almost eutectic)
alloys. Naturally, they would make a special alloy - but one has to be rich
for that. Consider as a last resort of plating more copper on top of the
copper for a result of at least a mil.

Perhaps dip the peizo into a solution of copper sulphate? CuSO4 plates most
metals with copper.

 

[John Larkin]

On 22 Mar 2005 16:01:04 GMT, Daniel Haude
<haude@kir.physnet.uni-hamburg.de> wrote:

Or use a spring.

No space.

--Daniel

Hmmm, piezo in UHV. Are you moving something a tiny distance, like for
an AFM or an atom probe?

John

 

[Daniel Haude]

On Tue, 22 Mar 2005 19:47:03 -0800,
John Larkin <jjSNIPlarkin@highTHISlandPLEASEtechnology.XXX> wrote
in Msg. <5jp141dh9djb6064uc4p8g057s0d0i7evs@4ax.com>

Hmmm, piezo in UHV. Are you moving something a tiny distance, like for
an AFM or an atom probe?

Yes, this is a piezoelectric stepper motor for an STM. I've built about a
dozen of them, but this is the first time I use copper-plated piezos. The
whole apparatus is described in Rev. Sci. Instrum. 75, 4871 (2004).

--Daniel

 

[John Woodgate]

I read in sci.electronics.design that Daniel Haude
<haude@kir.physnet.uni-hamburg.de> wrote (in
<slrnd406ig.g08.haude@kir.physnet.uni-hamburg.de&gt about 'Lead-Free
Solder: Weird Behavior', on Tue, 22 Mar 2005:

This is an STM that hangs inside a 14T magnet like a pendulum.

Oh, that's not playing fair! You aren't allowed to introduce a 14 T
magnet halfway through the speculations! (;-) Even so, your
current-carrying interconnections are prey to electromechanical
disruption. And BE VERY careful about using tin (Sn) at even modestly
low temperatures. Look here, and elsewhere with the search string
tin*allotropes:

http://www.physics.uoguelph.ca/summer/scor/articles/scor40.htm

ISTR that a few years ago, doubt was cast on whether 'grey tin' is
really an allotrope, rather than an intermetallic compound, but it seems
to have been redeemed.
--
Regards, John Woodgate, OOO - Own Opinions Only.
There are two sides to every question, except
'What is a Moebius strip?'
http://www.jmwa.demon.co.uk Also see http://www.isce.org.uk