# Trimmed gold fingers that still contain solder



## hammerdown (Sep 21, 2019)

Hello all!

For the past 5-ish years, I've been fascinated by the _HOBBY_ of "urban mining" and I have read a lot where & when I could and I've been stashing & sorting the various material as I get it from circuit boards. I didn't get into this for the delusions grandeurness of high profit or thinking of "getting rich quick"... like I said, just for the hobby and coolness factor of the aspect of mining for PMs from electronics... with intension of maybe "cashing-in" any recovered & refined PMs by retirement for extra Golden Years play money or to just leave to my children. To date, I have only been comfortable enough to use acetone to remove glue off PCBs, hot lye bath soft scrub for solder mask removal (works for me with no bad consequences despite some who claim it to be hazardous to the extreme) and mostly to run gold fingered material through HCL soaks and/or with a bubbler to aide, with just a smidgen of CuCl2 added to each batch to get the process started each time, and collecting foils (nearly 600ml worth of recovered foils in a beaker at present with more coming from batches still recovering and yet to run) afterwards to store for eventual AR or HCL/CL method to refine when I feel I'm ready to attempt. Yes, I have tried to read through Hoke's numerous times, but I get mind-numbed after a while since it seems more geared for dentists & jewelers for me to feel like I'm getting anything out of it, therefore I lose retention. So, hopefully I won't be dogged too harshly by my lack of chemistry knowledge when I post questions. And yes, I try and try to pan through the plethora of threads on here, which does at times help with whatever I am looking for at any given search, but not always clear & concise to my actual search inquiry... like what I'm about to ask about later.

That all being said, with my busy life of work, e-scrapping, family and other life-events, plus lack of proper ability for a separate secluded closed-in work shop with a fume hood and other proper ventilation (my current shop is where I work repairing computers and tear down scrap), I'm in a realization of that more than likely I won't proceed much further into this recovery & refining hobby than gold fingered material and clean cut-offs of other PCBs with just gold plating (if I suspect ENIG, I separate and have that stored separately since that'll create powders more so than foils from what I understand... which will lead into another question later of how to best process if I don't just sell as is), and will probably just sell off collected other sorted material I accumulate once or twice a year on eBay. I'm a bit turned off by tolling out given some horror stories I've come across over the past couple of years. At present, I have a decent bit of stashed up material (for what all I've been able to get as a part-timer at this)... 4 lbs of IDE pins, 4 lbs of MLCCs, ~5 lbs of RAM BGA chips, ~12 lbs of IC chips, ~4lbs of black top BGA chips, ~2 lbs EPROM chips, 3-5 lbs of mostly/fully gold plated various other metal material, ~3 lbs of somewhat gold plated various metal material, ~3 lbs CPU pins, ~3 lbs of fully gold plated various RF connector bits... to name some, plus much more of other types. 

Another stash I have that I would like to process, rather than just sell as-is is... I have 8+ lbs of trimmed various fingers where there's still quite a bit of solder up to, or damn near close to, the gold (I didn't trim these myself) and it would be very difficult & manually time consuming to attempt to trim cleaner, and I'm wanting to go ahead and try to recover the foils from this material over the next few weeks before it gets too cold here (NC) if possible. My question for this post is this... what would be the best step to proceed with these? Diluted HCL bath for however long to remove the solder in hopes of no gold foils coming off?... if so, what dilution ratio and how much heat from a hotplate if heat is advised? HCL+bubbler soak aided by direct sunlight to the covered bucket and deal with the hodge podge mix of gold and tin/silver (plus whatever else may precipitate into the mix) in another step? Would a HCL/Cl method be viable with little-to-no complications? Or is there no real viable way without major headaches in the end?... aside from attempting the daunting task of trying to trim these one by one closer to the gold? By the way, my HCL is from Lowe's in the blue label (JASCO Muriatic Acid) with the MSDS indicating 31%-35% HCL concentration... the "safer" green label is <30% according to the MSDS, but I don't buy that flavor. I did purchase some nitric acid from The Science Company a couple of years ago in the hopes of soon (as of then) being ready to use it, but I have yet to attempt to try it... mostly in fear of my lack of a fume hood and still feeling very "green" (no pun intended) at this hobby beyond accumulating material, research when possible and recovering foils off of clean trimmed fingers & PCB pieces. I'm sure this is a easy "problem" for most of you who are more experienced, but with me, I'm just wanting to minimize any possible headaches by going properly... not necessarily the fastest or corner-cutting way, which in turn could cause me more headaches. Once done with these, and other fingered material I have to process, I intend on attempting to recover copper from all my spent CuCl2 buckets and hope that no other PMs are in the solution. And although I know that stannous chloride is pretty much a necessity in this hobby, making stannous hasn't been a friend to me after many attempts, and I have heard a lot that it isn't wise to try and buy pre-made stannous due to shelf life. Anyways, any helpful direction would be appreciated on how to run these fingers with solder on them that I have. The science behind how & why on steps/methods (and the whynots of some other steps/methods) is nice & interesting and possibly useful, but direct directions helps me a lot too. 

Thanks.

If this question has actually been addressed in other threads, I so do apologize for I have not been able to locate them.


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## jimdoc (Sep 21, 2019)

I didn't read all that. But I would suggest re-trimming all the solder pieces off before you process.


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## glorycloud (Sep 22, 2019)

I wouldn't bother re-trimming the fingers unless you see components
still on the board or wires still attached to the boards. The solder
(in my experience) doesn't effect what I want to happen and that 
is to have the gold foils come off of the boards. I have pretty much
exclusively used the AP method over the last ten years of refining.

Solder and other "stuff" gets taken care of during the "gold cleaning"
after the gold foils are dissolved and the gold is dropped. There are 
a couple of gold washing procedures here on the forum that involve 
HCL washes and water washes. Pick one and follow the directions 
and your gold should be pretty pure when all is said and done.

I would imagine that you should end up with a nice shiny gold button
that weighs in at 12 to 14 grams. 8) 

Good luck!


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## anachronism (Sep 22, 2019)

Yup I think Glorycloud covered it pretty well. 

Jon


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## hammerdown (Sep 23, 2019)

glorycloud said:


> I wouldn't bother re-trimming the fingers unless you see components
> still on the board or wires still attached to the boards. The solder
> (in my experience) doesn't effect what I want to happen and that
> is to have the gold foils come off of the boards. I have pretty much
> ...



I pretty much figured AP (Cucl2 + bubbler in my case) would be the better way to go without trimming off the solder, but I thought I'd ask the forum just in case since I've not ran fingers with solder before. Thank you for responding and I plan on revisiting information on the various gold washing & refining methods once I'm ready... probably next year. Sorry my post was so lengthy.


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## g_axelsson (Sep 23, 2019)

If you have old copper chloride then you could use it to remove the solder. Copper will cement on the exposed gold and other metal surfaces, including the tin, while the solder will dissolve.

Starting a new batch with just a bit copper chloride can deplete the copper while tin and other base metals dissolve and the copper cement out. Just add more copper chloride until the other metals are dissolved, then the copper chloride leach will work just as normal.

I used old copper chloride to remove pins from pinned P4 CPU:s, soldered pins dropped off in just an hour or so, totally covered in copper.




Göran


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## hammerdown (Sep 27, 2019)

g_axelsson said:


> If you have old copper chloride then you could use it to remove the solder. Copper will cement on the exposed gold and other metal surfaces, including the tin, while the solder will dissolve.
> 
> Starting a new batch with just a bit copper chloride can deplete the copper while tin and other base metals dissolve and the copper cement out. Just add more copper chloride until the other metals are dissolved, then the copper chloride leach will work just as normal.
> 
> ...


Nice. I was thinking of using some of my old saturated cucl2 since I have ~40 gallons of it accumulated at this point. Although I have wondered which would be the better way... old cucl2 or fresh HCL for solder removal, but the thinking that I need to start cementing out copper from my many gallons of used cucl2 would probably make better use of what I got than creating more waste to deal with by buying more HCL... or would the fresh HCL way actually be better for ease & results purpose?


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## anachronism (Sep 27, 2019)

Saturated? I thought there was a way to revitalise it?


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## g_axelsson (Sep 28, 2019)

My experience is that cementing with copper chloride is a lot faster than using straight HCl to dissolve solder. It leaves copper on the gold but that is mechanical weak and pins can easily be scraped off the CPU:s.

Jon, copper chloride can be reused but the volume grows as more copper is accumulated in the solution. The excess is best to extract when it's exhausted and concentrated. I keep a couple of liters around as a starting point for new batches and the rest goes into my waste treatment (cementing, turning into hydroxides, filtering off).
Recently I started to look into an alternative way of treating the waste stream. It's a form of copper recycling that nurdrage showed on youtube. It takes some time and work but in the end you get the acid back and solid copper instead of creating a waste stream. What you need is a distillation setup, some sulfuric acid (reusable) and an electrolyze setup to electrowin copper and recreate the sulfuric acid.

Göran


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## anachronism (Sep 28, 2019)

Hey cheers Goran. I really don't use a Copper Chloride leach so thanks for the info.


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## hammerdown (Sep 28, 2019)

g_axelsson said:


> My experience is that cementing with copper chloride is a lot faster than using straight HCl to dissolve solder. It leaves copper on the gold but that is mechanical weak and pins can easily be scraped off the CPU:s.
> 
> Göran



Good to know since this will be my first go at finger material w/solder... thanks. I'm not dealing with CPU's right now. My intension is to run the whole 8 lbs as 1 single batch, which I'm sure may be more of a headache in the end when needing to rinse and whatnot, but we're down to maybe one week left of good summer-like temps & sunny skies and I'm ready to finish off this material for the season with the aide of nature's heat to aide lol. I was wondering if using an air bubbler for this would be useful or better to just let soak and stir every so often. My air bubbler is on the strong pressure side (16 gallons per minute), so a lot of agitation of the solution is created.


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## g_axelsson (Sep 28, 2019)

Acually, I've never used a bubbler with copper chloride. But then I've never been in a hurry and a couple of weeks or even months running time have never been a problem for me. Given time, oxygen will diffuse down through the surface and you can follow the progress of the emerald green CuCl2 going deeper over time.

Göran


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## Shark (Oct 1, 2019)

g_axelsson said:


> My experience is that cementing with copper chloride is a lot faster than using straight HCl to dissolve solder. It leaves copper on the gold but that is mechanical weak and pins can easily be scraped off the CPU:s.
> 
> Göran



I have been thinking about this for some time now and I am not sure what you mean by using copper chloride to cement with. The question would be is there a way to use old copper chloride to cement with from other solutions, such as the stock pot of AR solutions?

As for using an air bubbler it will help things along, I am just not sure why. The aggressive nature of the bubbles will knock some of the gold from the fingers, but is that a good thing if there is still base metals attached to it? I think the main thing of using an air supply is the greater surface area of the bubbles allows more contact with the solution allowing for a faster rejuvenation effect. It can allow for a rejuvenating effect from the bottom of the solution while the exposed surface is working it's way down from the top. I started using small portable type oxygen concentrator a few years back in place of aquarium pumps. (I found a couple cheap at a yard sale) I also use bubbling stones as it seems large quantities of smaller bubbles seems to work better for me. Of late I am in no hurry and use copper chloride differently now than when I first started, I tend to use it more like Göran does these days. I put my materials in it and come back to it when ever I have little material to work with.


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## FrugalRefiner (Oct 1, 2019)

An air bubbler provides circulation. That circulation does help to knock foils loose.

I used to keep aquariums, both fresh water and marine. I learned that while oxygenation takes place on the surface of the bubbles as they rise, and so the greater the surface area with smaller bubbles the greater the effect, most of the oxygenation actually takes place at the surface of the tank/solution. The circulation provided by the bubbler keeps fresh solution at that surface while oxygenated solution is moved throughout the tank.

Finer bubbles are better because they provide greater circulation. A single stream of large bubbles would rise through the solution without a great deal of disturbance, but many tiny bubbles tend to carry a lot of solution up with them as they rise, which is then spread across the top of the solution keeping everything in motion.

Dave


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## g_axelsson (Oct 1, 2019)

Shark said:


> g_axelsson said:
> 
> 
> > My experience is that cementing with copper chloride is a lot faster than using straight HCl to dissolve solder. It leaves copper on the gold but that is mechanical weak and pins can easily be scraped off the CPU:s.
> ...



The material I'm talking about is pins on CPU:s with soldered pins (green fiber PIII, P4 and so on). I'm using the copper chloride to dissolve tin, lead, iron and nickel by cementing the copper. When the copper cements out of solution the other metals goes into solution. In the end I'm left with the loose pins and the iron nickel alloy somewhat dissolved from the inside of the pins.

If you have seen how fast a piece of rebar can cement copper from copper chloride, the iron dissolves just as fast as the copper cements. Compared to using straight HCl to dissolve the iron from the pins, my feeling is that it is a lot faster. When the pins are off I pour off the contaminated copper chloride and replaces it with pure copper chloride to dissolve the copper that covers the pins now. The copper that cemented out onto the pins is quite fragile and breaks up into powder which is easy to dissolve with the fresh copper chloride leach, thanks to the large surface area of the powder.

And of course, you can do the same thing with any solution containing copper chloride, for example gold free solution from the stock pot. Only thing that might create a problem is other contaminants, but I can't think of a good example right now.

I hope it is a bit clearer now.

Göran


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## Shark (Oct 1, 2019)

Thanks, that makes sense. I have been missing that bit of usefulness of copper chloride.


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## DJPGold (Apr 19, 2022)

Am I correct in thinking that tin and etc left on gold fingers doesn’t matter if you intend to process them with the AP, copper 2 chloride process? The tin won’t affect the gold foils if they’re rinsed properly because tin is only really an issue when trying to dissolve gold hey


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## speed (Apr 20, 2022)

Yep the HCl will dissolve away the tin without issue.


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## Makcc (Apr 21, 2022)

This is not entirely true.
The hcl may react with tin and create stannous chloride.... And the fingers will lose gold to the solution as colloidal gold.
It can be recovered.


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## speed (Apr 22, 2022)

Nope. AP wont dissolve any gold if done correctly.


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## DJPGold (Apr 22, 2022)

speed said:


> Nope. AP wont dissolve any gold if done correctly.


Yeah, so what’s the point of your comment? We’re discussing doing it incorrectly in order to save time so the answer is is “yes, AP can risk dissolving gold if there is an excessive amount of tin remaining on the fingers prior to treatment with AP as the tin can cause colloidal gold to form”


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## Yggdrasil (Apr 22, 2022)

DJPGold said:


> Yeah, so what’s the point of your comment? We’re discussing doing it incorrectly in order to save time so the answer is is “yes, AP can risk dissolving gold if there is an excessive amount of tin remaining on the fingers prior to treatment with AP as the tin can cause colloidal gold to form”


Only if gold is dissolved somehow.
And gold can be dissolved to some extent if you overuse the peroxide.
Copper chloride leach as is the correct name will not dissolve gold by itself.
And as such will not form colloids with tin. However there can be colloidal gold trapped in the solder already by the soldering process. When HCl dissolved that tin it can form a very dilute colloid of gold. But that process has nothing to do with the copper chloride leach as such.


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