Soldering tiny wires of Pt/Ir

http://www.google.ca/search?hl=en&safe=off&q=platinum+%2Bsolderability&btnG=Search

Gosh! Golly! It is at least 2 years that I have consulted Google on this argument! The resukts were (as in this case): nothing of seful. My P R E C I S E question was: SOFT-Soldering of Pt/Ir is possible, Not or Yes (in this case, suggest the "Legieruns-Nr" in DIN EN 29453) ?

This non-answer falls under case "4. Et cetera, et cetera".

Please excuse my pedantry, but I will not accept non-precise responses.

P.S.: usually, the motto is: "Per aspera ad astra"

I used to make cauterizing tips from 50 μm PtIr alloys and the only guaranteed method of soldering was hard soldering with a silver alloy. This may not be a solution in your case so I would suggest micro spot welding would most likely be the best solution. Micro spot welders aren't that expensive and some battery supply companies carry them as they are used in the assembly of battery packs.

Your clear response is: SOFT-Soldering of Pt/Ir is not possible. Well!

In fact, I also have tried with success your method: I used a "Castolin-paste" (silver alloy) and a fan at 550 °C. After this, soft-soldering is easy.

Thank you.

P.S.: can you suggest some micro-spot-welder supply ?

I don't know where you are but I have guessed that you aren't in Australia so suggesting a supplier would be pretty pointless. I suggest you use the GlobalSpec website by clicking on the logo at the top of the page to find a local supplier.

Hello,

electrical resistance is possible if you get a capacitor discharge similar to spot welding.

simpler is to take an electrically conductive epoxi - we have good experience with this in similar difficult situations (Chromel-Alumel wires 20µm).

If you need operating temperature above 200°C then compression welding with pure silver is likely to work.

People at ww.uni-kl.de/FWT know this and more.

RHABE

Yes, the capacitor-discharge generally works well (with some mechanical pressure, in order to enlarge the contact area); even if it is a bit critical.

The weak point is mechanical, not electrical. But the 2-wires, when jointed with elect-discharge, may be forced to be parallel, then glued e.g. with cyano-acrylate.

This seems to me a good suggestion, and I will try to implement it.

The method of conducting-epoxy (also good), probably makes the junction ticker.

Thank you.

P.S.: I have visited the FeinWerkTechnik-site, but a treatment on the argument was not found. Then, I wrote to them: I will hope in a response.

These questioners always amuse me, thinking that they can demand an answer to their problem?!

Camillo, try asking for free advice with maybe a please or thankyou in your question - It really does help!

Electroman, thanks a lot for the wonderful and powerful suggestion!

In any case, the solution to this problem may be of interest not only for me, but for all that are working with very small thermistors, Pt100 et cetera.

Hallo,

if you really want to stay with soft soldering then - I think - it is likely that

the flux is the problem not the alloy.

If you try the stuff that is used to solder stainless steel it is likely that this may work.

Good luck

RHABE

use to make thermo coupler joints at a small semiconductor company yrs ago, as test eng i had to take a number of temp reading on the devices. i used a small bench "water jet" torch... neat device....did use water and some pressure from a chemical reaction of a metal placed in the chamber with the water ........wished i had studied it more and how it worked exactly.......for making the thermo joints... just twisted the wires and applied the jet tip of the flame.....the metals melted and fused into a small ball..... size of tip ball was what you formed up as you made it fuse

i have used simple tin lead formed as a cold solder joint ----but thats only good up to 180 cel.....anything higher and the solder joint rewets so you would have to fuse the thermo wire....but i also have just twisted the ends tight to... sorta makes a pressure contact ( remember hi speed wire wrapping posts ) and i think thats almost as good as a fused joint.

Thanks to those who've posted here. I just had good success soft soldering 0.2mm diameter Pt (Pt:Ir alloy? as used for electrophoresis electrodes in molecular biology gel tanks) wire. I twisted the ends together over about 15mm overlap, coated with silver soldering flux that i normally use for copper plumbing pipe soldering/brazing, heated that up with an iron set to 470C to give a good chemical clean, and then soldered the twist with 1.6mm flux cord solder that is 96.5% Tin, 3.5% Silver.