Lead-Free Solder: Weird Behavior

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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


Re: Lead-Free Solder: Weird Behavior


On 21 Mar 2005 16:06:19 GMT, Daniel Haude

>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.
>

It probably just dissolved all the copper away, then beaded up.

Considered conductive epoxy?

John




Re: Lead-Free Solder: Weird Behavior


On Mon, 21 Mar 2005 08:34:12 -0800,

> It probably just dissolved all the copper away, then beaded up.
>
> Considered conductive epoxy?

Yes, I'd use H20E. But this will take ages to do because I can't do all
the joints at the same time. Grrr. I'm reconsidering tin-lead solder, but
since this is a ultrahigh vacuum device lead is some sort of a no-no (too
high vapor pressure). Ultimately this is a low-temperature apparatus,
rendering vapor pressure a non-issue, but it also has to be
contaminant-free at room temp.

--Daniel



Re: Lead-Free Solder: Weird Behavior


On 22 Mar 2005 09:15:14 GMT, Daniel Haude

>On Mon, 21 Mar 2005 08:34:12 -0800,
>
>> It probably just dissolved all the copper away, then beaded up.
>>
>> Considered conductive epoxy?
>
>Yes, I'd use H20E. But this will take ages to do because I can't do all
>the joints at the same time. Grrr. I'm reconsidering tin-lead solder, but
>since this is a ultrahigh vacuum device lead is some sort of a no-no (too
>high vapor pressure). Ultimately this is a low-temperature apparatus,
>rendering vapor pressure a non-issue, but it also has to be
>contaminant-free at room temp.
>

The UHV guys tend to hate epoxy more than lead. The epoxy outgasses at
room temp and deposits organic crud everywhere, and some of that leaks
out later. There are all sorts of exotic lead-free solders. Some
people solder with pure indium which (I think) has low vapor pressure.

Try Kester or Multicore or Aim. They may have a lead-free solder with
some copper content, which might help the leaching.

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."

Or use a spring.

John




Re: Lead-Free Solder: Weird Behavior



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

Cheers!
Rich


Re: Lead-Free Solder: Weird Behavior



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Second only to nitrous.

John


Re: Lead-Free Solder: Weird Behavior


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

> The UHV guys tend to hate epoxy more than lead. The epoxy outgasses at
> room temp and deposits organic crud everywhere, and some of that leaks
> out later.

All possible, but we've been using epoxy forever and never had had
problems with it. Of course we try to not put the glue joints within
direct sight of the sample surface.

> There are all sorts of exotic lead-free solders. Some
> people solder with pure indium which (I think) has low vapor pressure.

Yes but it melts when you bake out the system at 150 degrees. And it makes
terrible joints.

> UHV is a huge nuisance.

Yup.

> 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."

Yup. That's me. And this is the reason why you develop superstitions and
hate to do something that you haven't done before, even if by any rational
argument it should be safe (like: If epoxy is OK, lead should be OK).

BTW the epoxies we use are those horrenduously expensive compounds from
Epotek, not your home-depot two component glue. It's semiconductor
industry stuff I believe.

> Or use a spring.

No space.

--Daniel


Re: Lead-Free Solder: Weird Behavior


On 22 Mar 2005 16:01:04 GMT, Daniel Haude


>
>> 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



Re: Lead-Free Solder: Weird Behavior


On Tue, 22 Mar 2005 19:47:03 -0800,

> 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



Re: Lead-Free Solder: Weird Behavior





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."

Or even "Let's heat it red-hot and pump it down for a week
or so while hitting it with a hammer every couple of hours."  :)



Re: Lead-Free Solder: Weird Behavior


I read in sci.electronics.design that John Larkin
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
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

I had something very similar happen when I tried to solder positive
tempco thermistor pellets between two brass sheets.  I was using tin
lead solder, and the result was similar to what you are getting.  The
extremely thin silver metalization layer was simply dissolving in the
solder and leaving me with an ummetalized die.  In my case, it was not
necessary to eliminate lead, so the solution (pardon the pun) was to
use 2% silver solder, minimum temperature and soldering time.  

Evidently your metalization layer is quite soluble (given the
temperature and time) in the solder you are using.  There is some low
temperature tin bismuth solder that might work better.

--
John Popelish


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
>
>
> I had something very similar happen when I tried to solder positive
> tempco thermistor pellets between two brass sheets.  I was using tin
> lead solder, and the result was similar to what you are getting.  The
> extremely thin silver metalization layer was simply dissolving in the
> solder and leaving me with an ummetalized die.  In my case, it was not
> necessary to eliminate lead, so the solution (pardon the pun) was to
> use 2% silver solder, minimum temperature and soldering time.  
>
> Evidently your metalization layer is quite soluble (given the
> temperature and time) in the solder you are using.  There is some low
> temperature tin bismuth solder that might work better.
>
You can (or could) get tin-lead solder that came pre-saturated with
copper, to prevent the solder from dissolving your tip or other valuable
things -- is it possible to get this same thing in lead-free solder?

--

Tim Wescott
Wescott Design Services
We've slightly trimmed the long signature. Click to see the full one.
Re: Lead-Free Solder: Weird Behavior



> John Popelish wrote:
>
>> Daniel Haude wrote:
>>
>>> 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
>>
>>
>>
>> I had something very similar happen when I tried to solder positive
>> tempco thermistor pellets between two brass sheets.  I was using tin
>> lead solder, and the result was similar to what you are getting.  The
>> extremely thin silver metalization layer was simply dissolving in the
>> solder and leaving me with an ummetalized die.  In my case, it was not
>> necessary to eliminate lead, so the solution (pardon the pun) was to
>> use 2% silver solder, minimum temperature and soldering time.
>> Evidently your metalization layer is quite soluble (given the
>> temperature and time) in the solder you are using.  There is some low
>> temperature tin bismuth solder that might work better.
>>
> You can (or could) get tin-lead solder that came pre-saturated with
> copper, to prevent the solder from dissolving your tip or other valuable
> things -- is it possible to get this same thing in lead-free solder?
>
   Yes; see my earlier posting in this thread.


Re: Lead-Free Solder: Weird Behavior


Behavior', on Mon, 21 Mar 2005:
>There is some low temperature tin bismuth solder that might work
>better.

Back in the Dark Ages, before 1930, people used Woods Metal to fix
galena crystals for crystal receivers into their holders. maybe it
should make a come-back. However, it's 25% Pb, so no deal....
--
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 Mon, 21 Mar 2005 21:06:10 +0000, John Woodgate

>Back in the Dark Ages, before 1930, people used Woods Metal to fix
>galena crystals for crystal receivers into their holders. maybe it
>should make a come-back.

It also used to be used for "trick" teaspoons that melted when you tried to stir
your hot cuppa.

> However, it's 25% Pb, so no deal....

That didn't stop them then ;-)


Re: Lead-Free Solder: Weird Behavior


On Mon, 21 Mar 2005 12:01:28 -0500,

> Evidently your metalization layer is quite soluble (given the
> temperature and time) in the solder you are using.

Yes, it goes away almost immediately even when I set the iron to a
temperature where the solder barely melts.

--Daniel


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
Are you using a different iron?.
Lead free solders, except special varieties designed to handle lead
contaimination, hate having any lead present. if you are using an iron
that still has a tinned coating on the tip from using a lead based solder,
it could give the behaviour you are seeing...

Best Wishes




Re: Lead-Free Solder: Weird Behavior


On Mon, 21 Mar 2005 16:21:05 GMT,

> Are you using a different iron?.
> Lead free solders, except special varieties designed to handle lead
> contaimination, hate having any lead present. if you are using an iron
> that still has a tinned coating on the tip from using a lead based solder,
> it could give the behaviour you are seeing...

That isn't it. The solder wets fine when applied to a thicker Cu surface.

--D.



Re: Lead-Free Solder: Weird Behavior


I read in sci.electronics.design that Daniel Haude
Solder: Weird Behavior', on Mon, 21 Mar 2005:

>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.

>
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 possibility of
getting a non-wetting alloy is much greater. Especially if you are using
phosphoric acid.

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

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