low emf solder
On Sat, 29 Oct 2016 01:39:12 +0100, you wrote:
On 28 Oct 2016 15:25, "Juris L" juris.l@gmail.com wrote:
I wonder how practical it is to weld test leads, so there's no solder or
thermal EMF.
I know that this will sound crazy, and probably is, but could one weld
components to a PCB?
I don't even have the excuse of been drunk or taking drugs, but I will
risk ridicule for making the above comment! Sometimes thinking out of the
box is useful.
Dave.
This can be done but whether it will help in the general case is
questionable because most parts do not use copper lead frames so the
thermocouple junction will be present whether soldered or welded.
On printed circuit boards, controlling temperature gradients and using
balanced circuits is usually sufficient.
In message CANX10hANKPjM3DKg8cEHSZcxLQC43pw0wpHkZHhdr6FENnESjA@mail.gmail.com, "Dr. David K
irkby (Kirkby Microwave Ltd)" writes:
On 28 Oct 2016 15:25, "Juris L" juris.l@gmail.com wrote:
Found reference to optimal emf solder composition cadmium/tin alloy
(70 %/30 %) in JJ array measurement article page 12.
I wonder how practical it is to weld test leads, so there's no solder or
thermal EMF.
I know that this will sound crazy, and probably is, but could one weld
components to a PCB?
The very first TTL ICs were not soldered but spot-welded to the PCB, we
have some of them in a RC4000 computer in datamuseum.dk and also the
people who designed and built the computer.
--
Poul-Henning Kamp | UNIX since Zilog Zeus 3.20
phk@FreeBSD.ORG | TCP/IP since RFC 956
FreeBSD committer | BSD since 4.3-tahoe
Never attribute to malice what can adequately be explained by incompetence.
probably because they drowned some lab rats with solutions of the stuff.
As we say in the health-physics business, "the devil's in the dose". If
I were working in a cad plating outfit, yeah, I'd check into what is
behind the IARC's somewhat arbitrary designation.
Making a small batch of cad solder at home? Reasonable basic
precautions apply such as don't chew on the ingot.
John
On 10/28/2016 05:33 PM, Neville Michie wrote:
LD50 is not the only consideration. From Wikipedia:
"The International Agency for Research on Cancer has classified
cadmium and cadmium compounds as carcinogenic to humans."
--
John DeArmond
Tellico Plains, Occupied TN
http://www.tnduction.com <-- THE source for induction heaters
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PGP key: wwwkeys.pgp.net: BCB68D77
On 10/28/2016 08:39 PM, Dr. David Kirkby (Kirkby Microwave Ltd) wrote:
I wonder how practical it is to weld test leads, so there's no solder or
thermal EMF.
I know that this will sound crazy, and probably is, but could one weld
components to a PCB?
Yes indeed. About 20 years ago I had a machine that made circuit board
by routing tiny wires and spot welding them to the connection. I can't
for the life of me remember that process name.
Only problem is, if you weld two different metals together, even copper
with different compositions, you've still made a very rugged and durable
thermocouple.
John
--
John DeArmond
Tellico Plains, Occupied TN
http://www.tnduction.com <-- THE source for induction heaters
http://www.neon-john.com <-- email from here
http://www.johndearmond.com <-- Best damned Blog on the net
PGP key: wwwkeys.pgp.net: BCB68D77
On 29 October 2016 at 14:51, NeonJohn jgd@neon-john.com wrote:
On 10/28/2016 08:39 PM, Dr. David Kirkby (Kirkby Microwave Ltd) wrote:
I wonder how practical it is to weld test leads, so there's no solder or
thermal EMF.
I know that this will sound crazy, and probably is, but could one weld
components to a PCB?
Yes indeed. About 20 years ago I had a machine that made circuit board
by routing tiny wires and spot welding them to the connection. I can't
for the life of me remember that process name.
Only problem is, if you weld two different metals together, even copper
with different compositions, you've still made a very rugged and durable
thermocouple.
John
But if one could use copper as the bond wire, rather than gold which is
quite common, then it would give you very little thermal EMF
I would have thought any impurities in copper wire, would be quite small,
as it would reduce the electrical conductivity. Whilst I accept one is not
going to get 100.0000000000000000000000 % pure copper, I would have thought
the effect of any impurities at least an order of magnitude less than using
solder. I'm only postulating this - I have no evidence to back it up, and
have never studied the subject.
Perhaps the person who was making the measurements on the solder, could try
making a thermocouple by welding two bits of wire taken from different
sources. I guess the problem would be preventing any impurities entering
the weld. A quick Google suggests one needs argon gas when welding copper.
Dave
On Sat, 29 Oct 2016 15:27:49 +0100
"Dr. David Kirkby (Kirkby Microwave Ltd)" drkirkby@kirkbymicrowave.co.uk wrote:
But if one could use copper as the bond wire, rather than gold which is
quite common, then it would give you very little thermal EMF
Copper is more and more used for bonding wires.
See:
http://www.ti.com/lit/wp/sszy003/sszy003.pdf
http://link.springer.com/article/10.1007/BF03214983
https://nepp.nasa.gov/files/26611/2015-370-Rutkowski-Final-Paper-NEPPweb-Copper-Wire-Bonds-TN26444.pdf
But be aware, that the bond pad on the chip is still aluminium in most cases
I don't know whether there is any process that uses copper bond pads at all.
As far as I know, all of the relevant processes for analog designs (ie those with node sizes over 130nm) still use aluminium interconnect only. IIRC the
first node size that got copper interconnect was 65nm and about 10 years ago.
I would have thought any impurities in copper wire, would be quite small,
as it would reduce the electrical conductivity. Whilst I accept one is not
going to get 100.0000000000000000000000 % pure copper, I would have thought
the effect of any impurities at least an order of magnitude less than using
solder. I'm only postulating this - I have no evidence to back it up, and
have never studied the subject.
The normal copper wires you get are usually 99.9%. If you go for the
oxygen-free variant you can get to 99.99% (don't ask me whether the
audiophool grade is really that pure). I have no idea how much the EMF
of the impurities is.
Attila Kinali
--
Malek's Law:
Any simple idea will be worded in the most complicated way.
On Sat, Oct 29, 2016 at 03:27:49PM +0100, Dr. David Kirkby (Kirkby Microwave Ltd) wrote:
Perhaps the person who was making the measurements on the solder, could try
making a thermocouple by welding two bits of wire taken from different
sources. I guess the problem would be preventing any impurities entering
the weld. A quick Google suggests one needs argon gas when welding copper.
Hello David.
I can test two different wires even without welding them, eventually.
This will not make a very durable thermocouple but if I clean them to avoid to
have a oxide layer, the result should be the same for the sake of measuring
thermal EMF.
I expect to have a very low signal to measure though. I must think to
experiment setup.
Best regards,
Andrea Baldoni
Am Sat, 29 Oct 2016 20:41:48 +0200
schrieb Attila Kinali attila@kinali.ch:
On Sat, 29 Oct 2016 15:27:49 +0100
"Dr. David Kirkby (Kirkby Microwave Ltd)"
drkirkby@kirkbymicrowave.co.uk wrote:
But if one could use copper as the bond wire, rather than gold
which is quite common, then it would give you very little thermal
EMF
Copper is more and more used for bonding wires.
See:
http://www.ti.com/lit/wp/sszy003/sszy003.pdf
http://link.springer.com/article/10.1007/BF03214983
https://nepp.nasa.gov/files/26611/2015-370-Rutkowski-Final-Paper-NEPPweb-Copper-Wire-Bonds-TN26444.pdf
But be aware, that the bond pad on the chip is still aluminium in
most cases I don't know whether there is any process that uses copper
bond pads at all. As far as I know, all of the relevant processes for
analog designs (ie those with node sizes over 130nm) still use
aluminium interconnect only. IIRC the first node size that got copper
interconnect was 65nm and about 10 years ago.
I seem to recall that either IBM or AMD used copper already in 90nm,
but that's still in the same ballpark. And I don't see a reason why
one shouldn't use copper bondpads if the better part of the
metallization is copper already to begin with. But on the other hand
with the aluminium backend you mention for 130nm and larger node sizes,
you're also in for some interesting material combinations: a) the
aluminium isn't pure but usually has a copper content of between 0.5
and 1.5%. Then b) the vias are usually not aluminium but Tungsten or
something similar. Aluminium is only found at nodes starting from about
0.5 micron upwards, with 3 or less metallization layers. And finally,
as aluminium doesn't stick too well to Silicon dioxide, there will be
thin layers of, say, titanium or titanium nitride in between insulator
and metal.
And please don't underestimate thermal gradients on chip. It's not
uncommon to see several tens of degrees difference in surface
temperature across even a small chip...
Best regards,
Florian
On Sat, 29 Oct 2016 20:41:48 +0200, you wrote:
On Sat, 29 Oct 2016 15:27:49 +0100
"Dr. David Kirkby (Kirkby Microwave Ltd)" drkirkby@kirkbymicrowave.co.uk wrote:
But if one could use copper as the bond wire, rather than gold which is
quite common, then it would give you very little thermal EMF
Copper is more and more used for bonding wires.
See:
http://www.ti.com/lit/wp/sszy003/sszy003.pdf
http://link.springer.com/article/10.1007/BF03214983
https://nepp.nasa.gov/files/26611/2015-370-Rutkowski-Final-Paper-NEPPweb-Copper-Wire-Bonds-TN26444.pdf
But be aware, that the bond pad on the chip is still aluminium in most cases
I don't know whether there is any process that uses copper bond pads at all.
As far as I know, all of the relevant processes for analog designs (ie those with node sizes over 130nm) still use aluminium interconnect only. IIRC the
first node size that got copper interconnect was 65nm and about 10 years ago.
...
Attila Kinali
Wide copper "straps" replaced gold and aluminum bond wires in high
performance power devices more than 10 years ago. I think I first
heard about it from IRC (International Rectifier Corporation) for the
drain connection in TO-220 power MOSFETs to improve the Rds(on) which
was becoming limited by the package. These days it is used with SO-8
and other packages as well.