# silver solder?



## hoardpm (Apr 25, 2009)

I hear the solder on circut boards referd to as "silver solder". Is that simply because of the color or is there actually silver content in it?


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## semi-lucid (Apr 25, 2009)

Good question. Older solder may not be likely to have much or any silver, but the newer lead free solder's are more likely to have some.

Read the lead free solder section in the link below.

http://en.wikipedia.org/wiki/Solder

John


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## peter i (Apr 26, 2009)

But not much silver! Typically 3½ percent.

That means, that the value of the tin in the solder is comparable to that of the silver, and you would make more money collecting the solder.

Chemical processing of alloys that contain tin is a pain in the a...! Dissolving tin in nitric acid yield a lot of slimy metastannic acid, that will clog filters and do all it can to annoy you!

In an industrial setting there are other possibillities, but for the recreational refiner, it will cost much more money than he will gain.


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## semi-lucid (Apr 26, 2009)

Peter



> you would make more money collecting the solder.



I was thinking the same thing after I posted. I've been looking for ways to deal with solder, I haven't found much information on the forum about it.

I've been trying to think up a good way to collect it, such as trying to get it to "emulsify" in a molten salt. In other words, de-populate the board with a molten salt, and then screen all the components out, and the collect the solder from the bottom

Getting it un-stuck from the other metals might be difficult.

John


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## dick b (Apr 26, 2009)

Your on the right track. To depopulate PCB's think about setting the board component side up in a bed of hot silica sand. Similar to the way they heat eyeglasses to soften the plastic so they can be adjusted.
The hot sand will melt the solder and wick some of it away by gravity. Then after it has melted, the board can be turned upside down and thumped into a collection pan catching the components. 
That way a quantity of the solder will be removed from the refining process and less chemicals will be needed to dissolve it.
The trick is to heat long enough to loosen the components without undue softening of the PCB. 
I do it that way, it's slow but it does work.


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## EDI Refining (Apr 26, 2009)

If any ones interested a have many pounds of un-soldered Sn/Ag material. 96%/4% Ratio. 
PM if interested


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## semi-lucid (Apr 26, 2009)

Peter H

Like Peter I said: "Chemical processing of alloys that contain tin is a pain in the a...!" And from what little I've read, processing tin electrolytically is not easy. 

I would guess that your buyers would be shops that are refining tin, like this one;

http://www.rotometals.com/category-s/60.htm

J


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## semi-lucid (Apr 26, 2009)

Does anyone know of a non toxic salt that melts at around 200 C ? (400 F)
And that is not extremely corrosive?

J


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## Lou (Apr 27, 2009)

Look into salt eutectic mixtures (i.e. CaCl2 and KCl or something like that)


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## nicknitro (Apr 29, 2009)

a gggg


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## AuMINIMayhem (Apr 29, 2009)

dissolving tin in nitric, I could see as being a "pain in the a--", but what about dissolving the solder in HCL.. then taking what is left rinsing it off with water and dissolving what is left (usually a grey/black powder) in Nitric?.. I know you'd wind up with a helluva lot of Stannous Chloride which may be handy.. not sure whether the silver values would dissolve alongside the tin or not.. just thinking out loud, feel free to tell me why this wouldn't work if indeed it wouldn't..


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## watlarry (Apr 29, 2009)

a mixture of 60 percent sodium nitrate and 40 percent potassium-nitrate melts at 430 degrees f not sure how corrosive it is.

http://www.sandia.gov/Renewable_Energy/solarthermal/NSTTF/salt.htm


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