# Soldering won't desolve



## Dougplogan (Jan 5, 2022)

I tried to digest the soldering off some cpu pins the other day. I used a coffee pot on a coffee maker added the pins and HCl. The next day soldering was smaller but still present. Let sit for two days to the point most of the foils are loose. At this point the foils are breaking up so lots of tiny gold specks mixed with tiny copper pins and some were dark some other base metal. I drained rinsed well with distilled water. Soldering still on bottom of pins. Did a nitric boil which has eaten all of the metal but leaving metastannic acid powder now. My question is this new soldier is mixed with silver right? It won't desolve in HCl but still puts tin in the nitric right? Just wondering not experienced enough to make guesses but I can deal with the metastannic if that's what it most likely is. Tomorrow I'll test and see if I'm wrong and see if this will desolve in fresh nitric before I try anything else. It boiled for several hours so I'm sure nitric is used up for the most part. Also just a note. I know when I first added nitric some gold would have gotten digested but so much copper was there it quickly cemented out. I varified that with Stan is tests


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## Martijn (Jan 6, 2022)

I think your hunch is correct. Test a bit of the solution with the tin paste for presence of silver with HCL.


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## Dougplogan (Jan 6, 2022)

Martijn said:


> I think your hunch is correct. Test a bit of the solution with the tin paste for presence of silver with HCL.


I did and yes silver. In a test tube I added solution and couple drops of HCl and yes it has silver.


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## Dougplogan (Jan 6, 2022)

Anyone know of a good way to remove the silver soldering from escrap? I'm reluctant to start a knew thread. I have started with just a couple oz of pcu pins but have more. And no doubt will run into this more in the future. Surely their is a better way than just dealing with metastannic acid.


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## Racoon (Jan 7, 2022)

Dougplogan said:


> I tried to digest the soldering off some cpu pins the other day. I used a coffee pot on a coffee maker added the pins and HCl. The next day soldering was smaller but still present. Let sit for two days to the point most of the foils are loose. At this point the foils are breaking up so lots of tiny gold specks mixed with tiny copper pins and some were dark some other base metal. I drained rinsed well with distilled water. Soldering still on bottom of pins. Did a nitric boil which has eaten all of the metal but leaving metastannic acid powder now. My question is this new soldier is mixed with silver right? It won't desolve in HCl but still puts tin in the nitric right? Just wondering not experienced enough to make guesses but I can deal with the metastannic if that's what it most likely is. Tomorrow I'll test and see if I'm wrong and see if this will desolve in fresh nitric before I try anything else. It boiled for several hours so I'm sure nitric is used up for the most part. Also just a note. I know when I first added nitric some gold would have gotten digested but so much copper was there it quickly cemented out. I varified that with Stan is tests


I did a lot of board repairs and I bought a desoldering station, with it I sucked about 90% of the solder. This will mean less to deal with using acid


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## Dougplogan (Jan 7, 2022)

Racoon said:


> I did a lot of board repairs and I bought a desoldering station, with it I sucked about 90% of the solder. This will mean less to deal with using acid


How does it work? I'm wondering if hot sand bath will take it off like that as well. Something better than a heat gun and butter knife scraping it off anyways


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## olawlor (Jan 7, 2022)

I've used fine stranded copper as a solder wick successfully on a tiny scale (for repairing electronics boards). 

I wonder if the copper powder you get from cementing out waste copper solutions on steel could be made to wick away solder? The copper would need to be very hot (soldering temperature is usually above 350C), very clean, and fluxed with something, because solder wick doesn't work if the copper is at all oxidized.


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## Dougplogan (Jan 7, 2022)

olawlor said:


> I've used fine stranded copper as a solder wick successfully on a tiny scale (for repairing electronics boards).
> 
> I wonder if the copper powder you get from cementing out waste copper solutions on steel could be made to wick away solder? The copper would need to be very hot (soldering temperature is usually around 400F), very clean, and fluxed with something, because solder wick doesn't work if the copper is at all oxidized.


Not a bad idea. Metallic copper powder is always at hand. Could mix it with sand in a hot plate and see if it will take off the soldiering. If trying to depopulate chips from boards I could see this working. Worth a try anyways. It would have to be alot with the sand I'd bet like 50/50 sand to copper powder. I'm not sure how pure that copper is though. It probably is mixed with other metals


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## GoIdman (Jan 14, 2022)

Dougplogan said:


> Anyone know of a good way to remove the silver soldering from escrap? I'm reluctant to start a knew thread. I have started with just a couple oz of pcu pins but have more. And no doubt will run into this more in the future. Surely their is a better way than just dealing with metastannic acid.



Regarding silver solder from PCB`s, just an idea,
I have tried with 50/50 success a trial closed shaking box for using with motherboards to remove solder and SMD.
It works fine to remove the solder and small SMD parts, but, man i tell you it stincks awful even with fumehood extraction, so i have abandoned the idea for now, until i find a better and safer solution with less burned PCB and gases.(those released compounds are no joke)

Be safe,

Pete


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## goldshark (Jan 15, 2022)

Makes me wonder if there is a composition out there which would work like a bone ash cupel. Is that what you are trying the emulate?


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## Geo (Apr 5, 2022)

Treat the pins in AP as normal and recover the silver at the end of the process. When collecting the gold foils from the AP process, recover ALL solids. Dissolve the gold foils (HCl and bleach works best) and filter out the solids. Rinse the gold chloride from the filter well. Incinerate the filter ensuring the material reaches a red heat and stays there for several minutes. Remove from heat and allow to cool completely. Put the material in a clean beaker and add 50/50 nitric acid and distilled water. Any silver chloride will have been converted to silver oxide and silver metal during incineration and will dissolve in the nitric acid.


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