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I have began to do an "art project" which utilizes solder as main material.

While I know that solder is cheap and easily found in multiple shops, I have set my mind on using recycled solder from out of use PCB's.

I've recovered a somewhat pure amount of material by using solder suckers, but a significant amount is trapped in my DIY desoldering braid which is simply salvaged wires. Those wires might be copper or some grey wires salvaged from a PC power supply.

What I have been able to come with is:

  • Some video I watched used (IIRC) $\ce{HCl}$ to dissolve solder from PCB's. My main issue is that I can't easily procure high concentration $\ce{HCl}$. My second issue is the acid reacting with the copper and maybe rendering the solder not usable (if this turns out to be a non-issue, I could figure a way to procure the acid).

  • I have been thinking of pulverizing the solder covered wires using a coffee grinder then heating the powder to the meting point of the solder, mechanically separating the two.

I wanted to ask if any of the two ways above would work without specialized equipment, or if there was a third way.

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  • $\begingroup$ Trying chemically recover solder from solder braid is a losing battle. $\endgroup$
    – MaxW
    Commented Sep 24, 2018 at 15:33
  • $\begingroup$ I can't imagine an individual collecting significant solder by these methods. Can you adapt zinc to your project ? Much,much more available and similar physical properties to solder. $\endgroup$
    – blacksmith37
    Commented Sep 24, 2018 at 16:07
  • $\begingroup$ @blacksmith37 here the "art" in the project comes in. I am trying to use recycled materials, and I don't have a source for zinc, that I know of. It was a try I guess. A futile try, as Max said. Thanks! $\endgroup$
    – Vlad Gamfaleanu
    Commented Sep 24, 2018 at 20:07
  • $\begingroup$ Zinc is very common in autos and consumer products , fourth most common after iron, aluminum and copper. Also called pot metal and white metal. $\endgroup$
    – blacksmith37
    Commented Sep 25, 2018 at 21:06

1 Answer 1

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Unfortunately the reason solder works is that it partially dissolves copper as shown in Figure 1 to form $\ce{Cu3Sn}$ and $\ce{Cu6Sn5}$ phases (also known as bronze) shown in Figure 2. Because of this you cannot simply melt solder off the solder wick to recover it as the tin will continue to dissolve the copper forming bronze. There is also the issue of needing rosin in your recovered solder to be useable. This 1960's video from NASA is an excellent video for learning more about the soldering process.

enter image description here
Figure 1. Reactions of the Copper-Solder Interface

enter image description here
Figure 2. Copper-Tin Binary Phase Diagram

To address the acid method. Physically, it could work (I would not recomend doing so with leaded solder) as most ROHS compliant electronics are $95\%+$ tin solders with either silver or antimony added as alloying agents to prevent tin whiskers from forming. That said it economically dissolving in acid then precipitating then reducing tin in a way which does not also produce copper would be a tedious and time consuming process. You are far better off just buying solder which does not cost that much and has rosin needed to flux the solder.

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  • $\begingroup$ First of all, thank you for your detailed answer, I am looking at the NASA video right now. My follow up question would be: would the acid way work? Not rendering the solder unusable after the separation would be something I don't want. Edit: Hit Enter too soon. $\endgroup$
    – Vlad Gamfaleanu
    Commented Sep 24, 2018 at 18:44
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    $\begingroup$ There is no way to use acid to leach the copper and leave the solder. $\endgroup$
    – MaxW
    Commented Sep 25, 2018 at 4:18
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    $\begingroup$ I would have written a very similar answer if I had seen the question first $\endgroup$
    – Nuclear Chemist
    Commented Sep 25, 2018 at 13:08

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