Gold Recovery from BGA chips - Full Process 

Hi Sam, thanks for the comment, yeah, you get it!

absolutely. since it involves gold, it draws people wanting money for nothing. They waste money and fizzle out. The people who love learning...stick with it, at least until they move onto bigger things - but gold recovery & refining is always in the skill set

One of my very first videos was a demonstration of how to melt Gold powder, so I never really bothered showing it after that. I'm already getting enough complaints that the videos are too long! haha. Thanks for the comment.

@@successfulengineer Thanks for your response & for what it's worth, I still say that seeing a nice shiny gold bead or bar at the end of the video is well worth the extra few minutes spent watching it.

Hi Moose, thank you very much, appreciate you taking the time to leave a comment.

Thanks for the message Shane, that was one of my first attempts, so pretty rough when I look at it now, but no arguing with the results.

Thanks for the great comment, appreciate it.

Hi there, sorry, haven't been keeping on top of the comments for a while. I would highly recommend starting with Gold plated fingers from Ram and cards as a first intro to chemical refining. Other than that, yes, it is a good idea to do it once at least if you can, as long as you take reasonable precautions, you will learn a lot and probably enjoy the process a lot. I still have the first little tiny button of Gold I first made.

Yep, when I look back at this video now I cringe a bit about my beginner technique, but cant' complain about the result.

@@successfulengineer The results is GREAT!! I've seen your newer vids and you have improved, but still alot to learn in this older one. I hope to be able to watch every one of your ewaste videos by the end of this year!! I'm planning on doing my own recovery and refining in the fall of 2021, after 4 years of learning about it!!

Thank you very much for the positive comment, there will certainly be a few more videos coming

Thanks Aaron, appreciate you taking the time to leave a comment. Feel free to ask if there is ever anything not quite clear enough in the videos.

Thanks for the positive comment Mike ! Ive got a few ideas for interesting videos to make, will get to them in the next few weeks :)

LOL! That's great, yeah, I started out with re-usable glass pipettes, but the disposable ones are wayyyyy better.

Thanks for the positive comment, I did miss out an important first step in the video as mentioned above in the description, soak your BGA chips in warm HCl for half a day or so to remove the solder from the bottom before incineration. Good luck with your recovery and be safe :)

Thanks for taking the time to leave a comment mate. Appreciate it.

@@successfulengineer it is my pleasure...

LOL, thanks for the comment mate!

Thanks for the comment!

Thank you for taking the time leave a message. I've got a few other systems for gold recovery that I'm working on at the moment, will post some videos soonish. Cheers

+Successful Engineer I'll keep watching.. Cheers my friend.

Thanks for the comment!

Thanks for the feedback Thomas, appreciate your comment!

Shut up Dumbass

This ain't no Dating site

Thanks for the comment, good luck with your recovery and be safe!

Thanks for the comment, I think the reason Copper is usually recommended is because it will happily cement out Silver, Gold and Platinum. By contrast Aluminium will also cement out Zinc, Iron and Lead. Having said that, it is only theoretical knowledge based on the reactivity series, haven't really done any deliberate Platinum recovery, so there could very well be some trick related to using Aluminium.

Hi there, this video is pretty old and crappy, but very happy if you managed to find some value in there! Thanks for the comment.

Yeah, that was an abnormally high yield, most of the chips were from the same type of server RAM, so I have been disappointed with BGA ram ever since ! Hahaha. This video is pretty old and my techniques were pretty crass, some of the later videos show better and faster ways of doing all the individual parts!

Hi there, great comment, thanks. I did switch over to Sulfamic denoxxing eventually, has made removing excess Nitric so simple compared to those early days of evaporating for days! My Nitric washes these days go into a separate beaker with some copper sheet for cementing out any pgms or silver which just goes into a big (retirement) jar. Thanks for the comment, appreciate your input.

It was a one-time wonder for me, it was all the same type of server ram and must have been especially good. In the years since around 2g/kg has been my average.

Hi there, thanks for the comment. The process in this video was quite basic, and as you point out, probably a little bit of losses in that initial wash. This video here -> ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-BQFNG_FXgZg.html is closer to the process I follow now. Much more controlled washing!

Successful Engineer cool I will be sure to check it out as soon as I can. 😊

Awesome, would be great to hear your impression / feedback on my 'better' wash process.

Green solution here was almost certainly left over Copper, I have too much HCl everywhere to have Silver in solution. Haven't really found small BGAs to have any significant amount of Silver in them.

Brilliant, I don't think that's a comment that has EVER been made on RU-vid before!

Thanks for the comment, I guess it depends very much on the country you are in, where I live, there are not many e-waste buyers, so people are generally pretty happy for you to take away their "junk". I found locating good scrap sources was pretty slow at first, but once you have built up a few contacts you can easily end up with far more scrap than you really want to process!

Sonny Zuniga Yes, sounds like you are progresaing well ! yes, I would usually have a bit of undissolved material left, you dont want too much carbon since it can absorb gold from solution, but Ive never had much trouble with that. Let me know how you go !

Hi Peter, technically, yes, there is still some ENIG Gold plating on some of the circuit boards, but it is incredibly thin and not worth recovering with the acid recovery method. All my harvested circuit boards basically go into a big drum which gets sold as low value board scrap to Ewaste buyers. I have a few videos showing the difference between ENIG and Hard Gold plating, would be worth a watch! Cheers

Yep, was a bit crude in this old video, I have significantly improved the overall process since then. Fine dust is a killer, definitely something you want to keep under control! Thanks for the comment.

Yes, unrealistic as I learned later, that was mostly one type of server ram, just happened to have a great yield. Overall I now expect about 2g/kg from general PC mixed ram bga.

Yeah, they definitely do once pyrolized!

You can incinerate in a open pan, there will just be a lot of smoke (poisonous, do not breathe) You also need to do at least 1kg of flat packs to have enough gold to really work with, so pyrolization then incineration is pretty much the way to go.

Hi mate, apologies, this is going back many years now, can't remember all the yields off by heart anymore. The BGA type ram can vary wildly depending on what you get, I have had as high as 10g per kg, down to more normal 2g per kg. Ram ICs with legs are usually around 1g per kg. Trimmed fingers I can't remember, but they are one of the most commonly processed ewaste, so should be plenty of yield numbers around for them.

Hi there, they are called ceramic plates, I got them from: www.labwarehouse.co.nz/Ceramic-plates_c_124.html which is a local company here in New Zealand. You should be able to buy them from any lab supply company local to you, they are usually very cheap. Appreciate your comment.

Hi Danny, a chemist may be able to tell you how to precipitate Tin that is dissolved in HCl, you can certainly cement it out of solution using Iron. You could also plate it out of the solution with electricity, searching for "growing Tin crystals" might give you some ideas.

Many thank's. Danny.

Thanks patnor1011, great information. That also explains why there seemed to still be copper in the mix after the nitric wash.

Sorry, I've got no idea regarding the legalities of marking and selling the precious metals. I've only sold gold once in button form, it was to a precious metal buyer and they had a XRF machine to check the purity.

Sonny Zuniga I would be very surprised if you dont have excess Nitric, does solution still test positive after you added SMB ? have you got some Sulfamic acid to denoxx ?

Successful Engineer no but I added a gold piece gonna let it denoxx overnight it's 222 am here gonna try again when the sun up

Did you have any more luck Sonny ?

yes 3.5 gram drop from 2.77 pounds of ram and bga and other flat packs I couldn't incinerate as well as I wanted and there was loss in carbon tons of work

Great man, that is actually a very good result for a first try. Doesn't sound like you lost much to carbon. You can always re-incinerate the carbon and treat it with AR again to see if it collected any gold. Yes, it is tons of work!

Hi there, thanks for the comment. Unfortunately the green fiber (flip-chip) intel CPUs have no bond wires, the only Gold on them worth recovering is the plating on the pins or the plating on the pads on the bottom. I have two videos that show the yield from both, unfortunately not much there!

That is a great bit of information, I will certainly give that a try next time. I have always assumed that the post drop reaction that I get is from the Pd and Pt still in solution, but it makes sense that it could also have something to do with the SO2. Thanks for the comments, always appreciate the feedbaci.

You are very welcome. Thank YOU for your time and experience in the videos. Help a LOT of us NEW people.

Thanks for the comment David, I honestly couldn't tell you the correct name, the supply place I got them just called them "heat spreaders".

Hi there, thanks for the compliment. Unfortunately the only gold in green fiber CPUs is the very thin plating on the pins, or the plating on the bottom in the case of pin-less CPUs. Green fiber CPUs are basically what is called flip-chip construction, so the die is soldered directly to the green fiber. You will see the same construction on newer north bridge chips, if they have the shiny silicon square on the top, they are pretty much worthless apart from a little bit of gold dissolved in the solder balls under them. I have a video where I look at various chips under the microscope that shows a lot this quite clearly.

Thank you! I wasn't sure what to do with them! I will take a look at the video you made regarding that! Thank you very much and please keep up the great videos! I find yours more informative than others!

Thanks for the comment / compliment Alvin. Appreciate your feedback!

Thanks for the positive comment, Ram / PCI fingers will usually yield about 0.5g per 100g of closely trimmed fingers. I haven't found any difference between the yields for fingers for older vs newer ram. Good luck and be safe !

AP is basically the process that is used to etch copper from circuit boards, so should work fine to dissolve any copper or brass base metals. AP works much much better when moderately heated (I use an aquarium heater in mine) and also get lots of air pumped through it with an aquarium air pump. HCl and bleach can certainly be used to dissolve the gold, it will be a bit slower than AR, but no reason it wouldn't work. Good luck with your recovery and be safe.

thanks for your concern and comment, really appreciate and will definitely give a try with AP solution

ThankGod Sylvester Omoigui No problem man, please let me know how the AP works out,would be very interested to hear!

Hi there, I have had very bad luck trying to pyrolise plastic connectors, they behave quite differently from epoxy in ICs. Now, having said that, I have seen (on youtube) videos where they show how to turn plastic into liquid fuel and what they are basically doing is heating the plastic inside a sealed container and distilling the gasses, so I'm sure if you do a bit of research you could find a way. The alternative that also works ok-ish is a hammer mill, like the one I made with spanning pieces of steel chain.

Thanks mate, as always good advice

Did you use a good microscope to look for the bond wires ? They are pretty much invisible to the naked eye. If you incinerated a few flatpacks, it is almost 100% certain that there will be some gold there. Did you see my video on using a microscope to look for bond wires ? You can incinerate a few flatpacks, then remove all the metallic legs, then treat the remaining material with Aqua Regia, then use Stannous Chloride to test the solution for gold. Just incinerating and looking for bond wires with your eyes will not work.

No didn't use microscope looked at only the bigger obvious wires

Yep, the bond wires are many many many times smaller than the chip legs. chip legs can be 0.8mm, bond wires are around 0.015mm. Have a look at my microscope video, you can see both chip legs and bond wires to get and idea of the scale.

Thanks for the comment !

Great comment, thank you! Yep, I started eventually using Sulfamic acid to convert the excess Nitric to Sulfuric, but you are 100% correct, a little squirt of sulfuric would almost certainly have precipitated a little bit of lead in that batch. Good luck and be safe!

The only

That came from 1kg of starting material, HOWEVER, this was from 1kg of mostly identical BGA ram from servers. I spent a lot of time being disappointed with the yields in following batches that had mixed BGA ram. The more usual yield from mixed BGA ram is around 2 to 3 g/kg.

Also, this was literally one of my first videos and later videos have much better processes.

Great comment, thanks aga

You should never pre-mix aqua regia, add enough HCl to cover your material, then add Nitric acid in small increments until all the gold has dissolved. Try not to use any 'extra' Nitric when you are dissolving gold. I can't remember what the exact real world Nitric usage works out to, but it's probably around 1 to 2 mL of Nitric for every gram of gold. If you start with some copper base metals in the mix, then obviously you will use more Nitric acid to dissolve those too.

Hi Sonny, I tend to answer all questions posted here, feel free to ask if you get stuck anywhere.

thanks alot

Definitely, this was done many years ago, one of my first experiments. Have been using Sulfamic acid since then for denoxxing.

Hi Sam, I'm guessing you mean how to wash out the acid AFTER dropping Gold ? Obviously you cannot do this before dropping Gold since the Gold is dissolved in the Acid. Yeah, start by siphoning off as much barren (test it) waste acid as possible, then wash the Gold powder with boiling water three times, clean Gold will stay settled during this washing. Then wash with hot (not boiling) HCl a couple of times, then another three washes with boiling water to wash the HCl out. The purpose of the hot HCl washes is to remove any Copper or Silver Chloride that may be left over.

Successful Engineer Thankyou! Is it the same process to clean the solution of acids before AR? I may have been referring to a later video of yours where you use hydrochloric then nitric to remove base metals, but then you must wash these out before AR process. How do you do this acid removal wash? Sorry hope this makes sense.

Hey Sam, yeah, now I get what you meant! Yes, when you are washing out the acids used to remove base metals, the best method is to use pH test paper and keep washing until the water pH doesn't change. (Hoke actually suggested somewhere that you "taste" the water and keep washing until it is no longer acidic, but obviously don't do that! :) ) Now, in practice, having trace amounts of acids left over is not actually going to cause major losses. The only issue with having trace HCl left before Nitric treatment is actually if there is Silver present, you will get Silver Chloride. Thanks for your comments and feel free to ask if anything needs clearing up anywhere, happy to help.

haha for sure

Good eye ! Yes, can't remember the brand, but I think that they are tops from tumble dryers. They are solid and plastic coated, so great surface for working on with acids (and free)

Hi there, that was starting with 1kg of chips from DDR2 server ram. That 6g was an exceptionally good yield because all the chips were from the same high yield ram. With mixed batches sometimes the yield can be as low as 2g per kg for these types of chips.

This was many years ago, but from memory it was around 1kg of very high yielding BGA ICs from server RAM.

Dankie man, groete.

Not really, I know there are a lot of "Gold recovery with household chemicals" type videos around, but the reality is that it might work in certain cases, but the more hazardous the chemicals are, the better they do the job for recovery unfortunately.

The gold 'plating' on phone boards is most likely to be a 'flash' plating, so not really that much gold there. Most of the values will be in the high pin-count ICs, but I would only expect somewhere between 2 and 8g per kg of ICs. Gold plated connectors also have a bit of value, but dangerous to recover. You need to study AP for the boards, a process like this video for the chips and reverse electroplating for connectors. Good luck and be safe.

Thanks for replying me .may I know is normal vinegar 3% concentrated can be used instead of muratic acid if I put it on fire to get out water to get more concentrate ? Forgive me I'm still beginner .thanks again ,

Not really, Muriatic acid (HCl) is very easy and quite cheap to buy. Look in hardware and swimming pool supply stores. There is some research going into concentrated acetic acid recovery, but as a beginner you need to make things easy, not difficult.

Hi there, just a DIY one, I live in the countryside, so didn't have any need for a particularly complex setup. I eventually started also using Sulfamic Acid for denoxxing solutions, which was great because I ended up not having to evaporate off so much Hydrochloric Acid.

would u have a video on how its built or a set of plans? thanks

No plans or video for it, but very simple and constructed out of plywood. I started with aluminium composite material, but the surface was attacked within the first few months. Have a look at the DIY section on goldrefiningforum.com - your requirements may change depending on your location and the amount of refining you do.

Thanks for the comment mate, appreciate it.

It is difficult to give you an exact number because every module has a slightly different weight. The best answer I can give you is it takes quite a lot of modules to get 1kg of chips, maybe about a shoe box full.

Successful Engineer ok thanks for that, another thing from me, how do you process the sruff that doesnt throug the sieve?

Good question, I am actually just processing some of it right now. Anything that cannot be broken up any further, I put in warm HCl for a while to remove the Tin, then I wash out the HCl+Tin, then form AR and leach the gold out.

It sounds like you are talking about a weak Copper(II)Chloride leach (Acid-peroxide process). But you haven't really specified which part of the process you want to replace with that. I can only assume you mean separating Copper from Gold ?

The BGA chips processed in this video was depopulated from computer RAM cards.

Hi there, I have a few different videos where I do different types of ceramic ICs, usually I just break them up (in my crushing mill), use a magnet to remove the legs. Then often just straight AR (Assuming there is no Tin present)

Hi Tawny, yes, you are the only commenter so far to really grasp just how fantastic that result was. Those were all chips from newer DDR2 and DDR3 memory (only BGA chips). With the older style chips with legs, you are lucky to get 1g/kg. It's a little secret with ram that you actually can't see most of the gold. Good luck with your recovery, thanks for the comment :)

yea thanks, the reason why I thought it would be less gold, was just because I had seen a documentation about gold and the fabrication of gold wire. They said there, its possible to make a 3 kliometer long wire out of a single gram of gold, so I didnt gave much attention to the chips,,,,, YET !!!! =)

I've never tried processing carbon, but I am starting to experiment with cyanide based leaches and was planning to recover the gold from the leach with carbon, so I guess I will have to figure it out very soon!

I assume you are intending to process the pins and not the fiber CPUs themselves ? The pins on those are usually Kovar (magnetic), so AP would not really be the right way. The gold foils on those pins are very thin, so I have never bothered recovering gold from them. I have seen a video where the person boiled the pins in HCl to dissolve away the Kovar, but it takes quite a lot of HCl. It may be worth it if you have a lot of them to look at a Cyanide based leach instead of acid, so you can dissolve the gold without dissolving the base metal.

Successful Engineer I have just 365 grams thinking of Ap and just let them run it's course thank you

AP is a copper etch method, the pins from those CPUs will be magnetic, so they will be iron based, not copper. You can probably just leave them in straight HCl if you are not in a hurry. No benefit to put them in AP.

I'm sorry I meant I'm processing in AR hoping this will be ok got I'm a hurry

Yes, AR should work OK, for 365g you will use quite a lot of acid. You will need to keep on dissolving until all the metal is dissolved, otherwise the gold will cement out of solution on the iron as a fine black powder. Let me know how it worked when you finish.

Fume hood exhausts from the top left into a tower behind the shed. We live in a high-wind zone, so sufficient for refining a few grams a week.

For sure, I was always a happy camper when I could look at a solution 15 minutes after precipitation and it's already cleared up! also makes washing the Gold that much easier when it is nice and clean!

Perfect, that's a good way to go, I prefer the oven because dealing with the waste acid is such a pain the back, but did experiment once with running whole RAM modules in AP. The only other pain I had was trying to separate my foils from the small resistors and capacitors, but honestly, you can probably AR the whole lot and it will almost certainly work fine.

How about pins from ceramic and fiberglass? Any suggestions? I've removed nearly all with a heat gun. But I'm not sure of the best way to process. I haven't found a video with anywhere near the detail on that process like yours on the chips

Do you mean CPU pins ? If so, I haven't bothered to run any CPU pins yet, I believe the yield to be quite low on most modern CPUs. But . . . there will be two types of pins, strongly magnetic (iron/kovar) and weakly magnetic (brass), for the kovar pins, you want to boil them in a stoppered flask in HCl to get rid of the base metal. For the brass pins, regular AP will work. Either process is quite slow because you essentially have a tube of gold filled with unwanted base metal, and you can only attack the base metal from one open end. At that point it may also be worth looking at leaches that will remove just the gold and leave the base metal (cyanide type stuff) or alternatively you could look at removing the gold through reverse plating (concentrated sulfuric cell).

This was quite a long time ago (my technique has improved dramatically since back then!), but I believe this was 1kg of small BGA chips from server DDR2 or DDR3 ram.

from 1 kg ddr unreal 6.5 g

@@armrosdmg9410 It was DDR2 or 3, not sure. And they were all identical modules recovered from tearing down servers. That was a particularly great result, I usually expect 2 to 3g per kg from random mixed DDR2 / 3.

Hi Robin, sorry for the late reply, the vast majority of ICs going into this batch was from 1 type of server ram. (DDR2 / 3) A supplier of mine had broken down a truck load of identical servers and I think they just happened to have fantastically high yielding ram. It was actually a bad start for me, because I then spent wayyyyy too much on general DDR2 and 3 ram after that trying to recreate this. After many many batches, I would expect more like 3g/kg for DDR2/3 ram. Black-top Gold corner chips are more like 10g/kg.

@@successfulengineer No worries and thank you for the reply, i have alot of ram to go through and up til the aqua regia process been quite successful. I think i didnt do so well on boiling off all the nitric and the smb process didnt seem to run smoothly. I think i have much to learn, thank you for all the videos.

@@robinlowther1826 Hi again, the evaporation process for getting rid of excess Nitric acid is very slow and tedious, I would recommend you look into using Sulfamic acid for denoxxing, once I started with that, I never looked back. Feel free to ask if you are ever stuck, always happy to help where I can.

@@successfulengineer have you used urea for denoxing? Seems more readily available. Thanks for the tutorial

@@successfulengineer Thank you i do have some sulfamic acid but have not tried it for denoxxing. Im just going through another kg of chips trying not to wash away the gold, fun times. Do you have a video of that process, and thankyou again for the reply.

Hi there, not sure which part you are referring to, could you post a time in the video ?

Hi! theoretically it would be great if you could write the whole procedure you described in the video (which is really well made), because those who are not native English speakers (like me) certainly has trouble understanding all the words. however, since I think I know the original proceeding, I can not understand what you explain after 33 minutes and 40 seconds. greetings and thanks

OK, I think I understand where we are. At that point in the video, the Aqua Regia has dissolved all the gold into solution, but usually there is still some 'unused' Nitric Acid (HNO3) in the solution. We cannot precipitate the gold out of the solution while there is still HNO3 in the solution, so we must remove it somehow. The way I remove it here is by evaporating the solution at around 80 deg C until there is only a little bit of solution in the bottom of the container and the solution becomes like syrup. Then I add a small amount of HCl and repeat the evaporation process two more times. After this, all the HNO3 should have evaporated off, and we can precipitate the gold from the solution. Hope this helps!

Maybe I understood. You manage to precipitate the gold without adding either potassium metabisulfite nor urea, then using the heat and the addition of water. Am I right? Thanks a lot

No, I precipitate the gold using Sodium Metabisulfite that is dissolved in water. It looks like clear water in the video, sorry, I didn't show where I dissolved 10g of SMB in the boiling water. I didn't use urea to neutralize the HNO3, I evaporated the solution 3 times with HCl addition to get rid of the extra HNO3.

Yep, sounds about right. That button was part of a bit of Gold I sold last year, XRF'd @ 99.8% pure. I'm aiming for 3 ounces this year, got about 2 ounces 10 grams at the moment. The 1 ounce buttons do look and feel very impressive.

Hi there, I think we have a problem with the translation, could you add a bit more detail ? Thanks. It could also help if you post in your native language.

I would like you to help me tell me what to do to get clean gold

Do you mean how to refine gold (dissolve it with Aqua Regia and precipitate pure gold) or how to clean the gold powder once it has been precipitated (by washing)

Nick Stoyles All the chips in this video came from RAM sticks, I have used this process successfully on all different types of ICs

Successful Engineer I asked the question before watching this video. I got confused by the title you see. I didn't know bga chips were the same as ic chips. I've got just over 4kg of ic chips to process and I've been looking for a video on how to process them. yours is definitely the best 1 I've seen onhere. I hope I get as much gold off mine as you did off yours.

Thanks for the compliment Nick, yes, BGA = Ball Grid Array, which is the way the IC solders to the PCB. Many people assume that BGA is only the north bridge type chips, but really all BGA chips yield reasonably well. Good luck with your recovery, let me know how you get on. Cheers

I finally got around to incinerating 500 grams of ic chips over the weekend. I thought I would start with a small amount in case I messed it up. I sieved the ash and removed the magnetic pins. I then ran the ash through a blue bowl. I actually recovered way more magnetic pins than non magnetic. I would estimate about 5 grams of non magnetic and around 200 grams of magnetic. Is that normal?

Hi Nick, glad to hear you are progressing, it is very intelligent of you to start small, you wouldn't believe how many people start big only to end up with a big mess. I have never directly compared the amount of magnetic vs. non-magnetic pins, but I wouldn't be surprised. Kovar (iron based) is very common for IC legs because it expands at the same rate as the silicon die and is probably a bit cheaper than copper. Did you sieve the material down until almost all the legs were removed before using the blue-bowl ? I find it to be much more successful if the particle sizes are similar. Let me know how you progress!

That method is pretty old now, I made a rotating trommel type automatic depopulator a year or two ago. Can do a a kg of ram in a few minutes from memory. Putting entire RAM modules in AP is a bit crazy, you would create an enormous amount of waste acid for the Gold yield. That's why we trim the fingers closely before using AP, less acid usage, less waste to deal with. I almost always prefer automated mechanical processes over chemical

Successful Engineer i just reuse it...ad hcl

Especially ram has gold all over the board anyway, along with other metals. It cleans the boards.

The Gold on the ram boards (apart from the fingers) is ENIG, it is an incredibly thin coating. The problem is that you are dissolving a lot of Copper, saturating your AP (which is when you have to add more HCl as you said). All this AP is incredibly toxic and goes through time consuming waste treatment. But at the end of the day you only end up with 0.1% more Gold for dissolving 500% more Copper. I try to keep my waste generation to the absolute minimum so I only have to treat the waste once every 6 months or so.

Hi

I assume you mean with zinc ? Yes, you can cement gold out of solution using Zing, I would probably use copper instead, but you will not get the same purity as precipitation with SMB.

Successful Engineer gracias☺

Yep, I'm always telling people not to bother with ENIG on circuit boards, but I don't think they believe me until they try it for themselves.

Successful Engineer Now i'm ready. Electro reduction recycle. thank you for your coment