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Re: Lead-Free Solder: Weird Behavior


On Mon, 21 Mar 2005 16:32:27 +0000,

> Yes, your experience seems to indicate that. But it may not be just
> Cu/Pb. I doubt that the Cu is plated directly on to the piezo material,
> and if there is, for example, a Ni interlayer there

The mfg (Staveley Sensors) says no. They usually go Piezo-Cu-Ni-Au (if you
want gold). Nickel solders by far the best, but it's magnetic.

> Try using lead-free solder made for **electronics**, not the Sn/Cu stuff
> used for plumbing.

I tried both (two kinds of electronics stuff and one of the other)
with the same results.

--Daniel


Re: Lead-Free Solder: Weird Behavior


I read in sci.electronics.design that Daniel Haude
Solder: Weird Behavior', on Tue, 22 Mar 2005:
>The mfg (Staveley Sensors) says no. They usually go Piezo-Cu-Ni-Au (if
>you want gold). Nickel solders by far the best, but it's magnetic.

Not very (and if it's alloyed it may even not be ferromagnetic). You
would likely get more magnetic effects from the currents in the
interconnections.
--
Regards, John Woodgate, OOO - Own Opinions Only.
There are two sides to every question, except
We've slightly trimmed the long signature. Click to see the full one.
Re: Lead-Free Solder: Weird Behavior


On Tue, 22 Mar 2005 12:04:11 +0000,

>>The mfg (Staveley Sensors) says no. They usually go Piezo-Cu-Ni-Au (if
>>you want gold). Nickel solders by far the best, but it's magnetic.
>
> Not very (and if it's alloyed it may even not be ferromagnetic).

I know it's definetely "not very", but what little there might be could be
too much. This is an STM that hangs inside a 14T magnet like a pendulum.
We found that the current model gets deflected by 1mm to the side already
at 4T. My hunch is that this is due to the nickel interlayer that was
carelessly applied when the whole thing was gold-plated. Now I'm building
a replacement and am trying to ban all ferromagnetic materials whatsoever.

That said -- I tried to make a nickel-plated 1/2" piezo scanner tube roll
on a flat surface by holding a strong permanent magnet (from a harddisk)
next to it. Nothing. That was of course at room temperature; who knows
what happens at .3K. After a few years of working with materials under
such conditions you develop a superstition.

--Daniel


Re: Lead-Free Solder: Weird Behavior


I read in sci.electronics.design that Daniel Haude
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
We've slightly trimmed the long signature. Click to see the full one.
Re: Lead-Free Solder: Weird Behavior


>I read in sci.electronics.design that Daniel Haude
>Solder: Weird Behavior', on Tue, 22 Mar 2005:
>>The mfg (Staveley Sensors) says no. They usually go Piezo-Cu-Ni-Au (if
>>you want gold). Nickel solders by far the best, but it's magnetic.
>
>Not very (and if it's alloyed it may even not be ferromagnetic). You
>would likely get more magnetic effects from the currents in the
>interconnections.

This isn't likely in a piezo device since the DC currents are very very
small.  There is nothing in the universe more magnetic per pound than a Ni
plating.

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



Re: Lead-Free Solder: Weird Behavior


I read in sci.electronics.design that Ken Smith
about 'Lead-Free Solder: Weird Behavior', on Tue, 22 Mar 2005:

>This isn't likely in a piezo device since the DC currents are very very
>small.

But what about the supplies to whatever is connected to the piezo?

> There is nothing in the universe more magnetic per pound than a Ni
>plating.

I find that astonishing. Ni plating is more permeable than, say,
Permalloy C, or has a higher coercivity than barium ferrite, or what?
--
Regards, John Woodgate, OOO - Own Opinions Only.
There are two sides to every question, except
We've slightly trimmed the long signature. Click to see the full one.
Re: Lead-Free Solder: Weird Behavior



> Hello,
>
> I've been trying to solder wires to copper-plated piezo actuators using
> lead-free electronics solder. It turns out that within a fraction of a
> second I get something that resembles a solder joint, but then the solder
> immediately retracts to other parts of the surface, leaving behind a
> dullish-grey area that won't wet any more no matter what I try.
>
> I've been soldering piezos a lot, and I've been using lead-free solder a
> lot (the stuff used for plumbing; it has a higher melting point than the
> electronics stuff but is otherwise a similar alloy). Only I've been using
> nickel- and gold-over-nickel plated piezos which solder like a charm.
>
> Problem is that in my application I can't have lead, and I can't have
> magnetic material.
>
> I've tried to scrape off that grey layer, but it seems like I hit the
> piezo material right away. I can't tell if I have any copper left because
> the copper is only some three microns in the first place.
>
> Of course the stuff solders as expected with lead solder (which, however,
> won't stick to the surface spoilt by the lead-free stuff).
>
> Could it be that the lead-free solder dissolves copper to form some
> un-solderable alloy? Sounds odd since the solder alloy contains some
> copper itself.
>
> The flux is not the culprit; I'm using both resin and a phosphorous
> acid based stuff, and both don't affect soldering with lead-containing
> solder.
>
> Any hints appreciated,
> --Daniel
   Firstly, it is known that there is a problem with (standard tin-lead)
solder on gold.
   It works very well, and looks super when done.
   However, as time goes on, the solder will seperate from the gold as
if nothing was done.
   The solution to this is a standard practice: slobber solder on,
remove and sloober again - until all the damn gold is leached from the
surface; *then* solder the connection.

   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.

   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
* Sn 96.5, Ag 3.5 - MP 221C / 430F
* Sn 95, Sb 5 - MP 232C / 450F
   Of all of these, i would strongly recommend the first, because it
does have copper and would be less likely to leach copper from your parts.
   And it is clear from your description that leaching is the primary
culprit.


Re: Lead-Free Solder: Weird Behavior


On Mon, 21 Mar 2005 21:36:07 GMT,

>    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


Re: Lead-Free Solder: Weird Behavior



> On Mon, 21 Mar 2005 21:36:07 GMT,
>
>>   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.


Re: Lead-Free Solder: Weird Behavior


>
>>
>>> 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.


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