Silver Soldering Platinum

[H.Durstling]

Hi Folks, I’ve been contacted by a physicist friend from a nearby
university, asking of I can silver solder (re-solder, actually) a
thin strip of platinum onto a contact post in some sort of high-tech
laboratory measuring device.

The platinum strip is actually a very slender foil 30 microns thick
by 1/2 mm wide; he compares it to a Christmas tree icicle. One end is
still attached to its contact; the other has broken loose (“I did
something I shouldn’t have,” is how he put it.)

The device has something to do with temperature measurement or
temperature control. Parts of it get up to 700 degrees Celsius, but
the contact itself has a heat sink which keeps its temperature to the
200-300 degree range. I haven’t seen it and have no idea whether it’s
even physically possible to get in there with a small tip torch flame
without doing damage; I’ll look at it on Saturday.

Never having worked with platinum before, my question is can it be
silver soldered at all? Will the silver solder adhere?

The second question is, I plan to use my acetylene torch. Not
oxy-acetylene but only acetylene, with the smallest tip I have. But
I’m told that the acetylene flame is rich in unburnt carbon; and I do
remember reading that carbon in platinum is harmful in some way. What
does it do to the platinum? Am I putting the platinum foil strip im
jeopardy by going at it with the acetylene torch?

Any informed advice and speculation will be greatly appreciated -

Cheers & thanks,
Hans Durstling
Moncton, Canada

[rexsmerten]

Dear Hans Durstling, It may help to know that I have successfully
soldered platinum to fine silver in some experimental enamelling
work I’m playing with. (Enamel colours respond very differently when
they are fired on silver and platinum and I’m exploring colour change
within the one piece of jewellery)

I doubt whether you will need to even use an acetylene flame, and
yes, it is very sooty with carbon. I would have thought that a
conventional gas-air flame combination would have been sufficient.

Without knowing more about the instrument to be repaired, would it
be possible to slightly change the broken contact point by soldering
a pin to the platinum strip and then rivetting or somehow fixing it
without soldering to the contact point? This might avoid the problem
of the heat sink. Just a thought, and lots of luck. Kind regards, Rex
from Oz

[YUKHAN]

acetylene flame is rich in unburnt carbon 

you will have to use propaine or hydragen(even better),the carbon or
anything else will contaminate the plat. also i’mnot sure the silver
will hold up to thosekinds of heat,best to use some 1000 degree
solder. good luck!

just another note laser welder might be better

ROBERT L. MARTIN
Gold Smith / Diamond Setter
yukhan@aol.com

[Judy_Willingham]

Hello Hans, Could you use a low temp solder like TIX? Ask your
physicist friend if the type of solder is critical. Perhaps after
you see the still attached contact, another idea will come to mind.
Good LUCK! Judy in Kansas

Judy M. Willingham, R.S.
Biological and Agricultural Engineering
237 Seaton Hall
Kansas State University
Manhattan KS 66506
(785) 532-2936

[David_E.Barzilay]

Hans, this sounds like a job for laser welding. If you don’t have
someone locally, we have several in ellay (Los Angeles) who could do
it. David Barzilay, Lord of the Rings

[Peter_W.Rowe]

  Never having worked with platinum before, my question is can it
be silver soldered at all? Will the silver solder adhere? 

Yes. It will work just fine.

       I'm told that the acetylene flame is rich in unburnt
carbon; and I do remember reading that carbon in platinum is harmful
in some way. What does it do to the platinum? 

You won’t have to worry about it at silver soldering temperatures.
The problem occurs at platinum melting and soldering temperatures.
As I understand it, the problem is that at thise high temperatures,
carbon is a very good reducing flux, and is able to reduce silica or
silicates in various forms to metallic silicon, which then alloys
with the platinum and causes brittleness. silica or silicates, etc,
are common a jewelers workshop, being in fluxes, soldering boards,
various other items. hard to avoid, and normally harmless. But
with carbon present, it causes contamination of the platinum.

Hope that helps.
Peter Rowe

[Wayne_Emery]

Hans, Let me be kind and please try to trust me on this pass on the
Pt job, it is not one for a beginner or an acetylene torch No
offense is intended, but you do NOT have the skills necessary for
this and you stand a good chance of demolishing this piece

Wayne Emery

[Peter_W.Rowe]

Hans, Let me be kind and please try to trust me on this pass on the
Pt job, it is not one for a beginner or an acetylene torch No
offense is intended, but you do NOT have the skills necessary for
this and you stand a good chance of demolishing this piece

Wayne, DO keep in mind that Hans was NOT asked to do a platinum
soldering job. He was asked if he could SILVER solder a platinum part
back together. his torch is air/acetylene, not oxy/acetylene. that
job ends up being no different from silver soldering two pieces of
silver together with that torch, except that since at least one half
of the joint is platinum, then at least there’s that one half he
probably has less risk of accidentally melting. For silver
soldering, the air acetyelene torch he’s got, while perhaps not the
best possible choice, should still be reasonable, if he’s got a small
tip and the parts are not too small for him to get into the joint area
without damaging adjacent parts or something. The simple answer to
his question is that yes, silver solder will adhere well enough to
platinum, and that the excess carbon problem with his torch is not,
in fact, a problem in this case. Now, whether he’s got the skills to
do a decent silver soldering job is another question entirely…

cheers
Peter Rowe