Electronics > Metrology

low thermal EMF solder

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Hello - I am looking for a source to supply low thermal EMF solder - can anyone provide pointers ?

In the past a cadmium - lead alloy was used for this, but these are banned (RoHs) ... - the aim is to minimize thermo-couples on a very sensitive 4 layer printed circuit board - 0.1ppm / K on a 10V full scale - so every 100nV we can reduce is taken under consideration (preventive actions)

The assembly factory is located in Belgium.

Thank you for all feedback !

Dr. Frank:
Just to finish your search quickly:
We habe discussed that on volt-nuts already,  Cd based solder really is not available any more, and nobody found an alternative, either.


kapptec solder google it.
I cant find any vendors, most others are hard solders, so that is a sign.

how difficult is it to craft this solder? I assume the lower melting point materials are melted first, then the silver metal dissolves in them due to solubility rather then temperature.

Both elements can be bought in high purity fairly cheap, what are the ratios?
Is anyone interested in buying some home made Cd-silver solder?

Sure, I cannot offer you a flux core, but it should still be highly usable. I assume it is only used around references ETC, not the whole PCB?

it could be easily melted under an argon shield aswell if oxide contaminants are a concern, with metal pre-treated with mineral acids to remove oxides.

how hard is this stuff? can it easily be cast? what is the maximum solder diameter that you would consider useable? how much would you be willing to pay by weight?

well I am interested in this stuff now too and I want some, I will make it for myself if there are no sources. Cadmium rod is damn cheap on ebay...

for production what do you need, solder paste? I think home made solder rod would be appropriate for through hole, but SMD thin solder would probably require some kind of special extruder machinery, unless you are like my friend and some how manage TSSOP with "pipe solder" and a 10$ soldering iron (while I need a nice iron and 0.7mm or less solder)

I imagine that you are probably using through hole technology if you are worried about thermal EMF, due to strain and whatnot.

But I do wonder if you could melt the alloy then grind it up in a chilled ball mill and put it through mesh sieves and mix it with flux... i bet robrenz would be interested in this ...
or is it produced through atomization and cooling (for spherical particles), not that hard a task for low melting point solids..

do you have any literature about the chemistry of these low emf solders?

i think realistically you need to contact a solder paste manufacturer and ask them if they can do a special batch for you, you could try a kick starter or something like this when you get a quote for low EMF solder production to manage the upfront costs, I'm sure some people might be interested.

i wonder if you can mix up the alloy yourself and then just mail it to some kind of factory to save money, i wonder how hard it is to make an alloy


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