Green and cloudy AR???

[AndrewSuperD]

Hi folks. Quick question. What did I do wrong? Ha! I processed 100g of mixed BGA (copper top and no copper top). I mechanically separated top from bottom. I incinerated the tops. Stored the bottoms for “maybe one day”. I separated the copper heat spreaders and put the remaining ashes in my ball mill for 1/2 day. I left the die in there too. Once powder, I gravity separated with water and beakers until I had maybe 50ml of material left. I went straight to AR with a stir bar and heat of 80C. Stir bar and die pebbles probably not good for my beaker? Anywho, I added 150ml HCl (31.5%) and 32 drops of concentrated Nitric in two sets of 16 until reaction stopped. I added another 100ml HCl and another 8 drops of nitric just to ensure no reaction. Left the beaker cook for 10min between all steps. I added Sulfamic while still hot till no reaction. Pulled off heat and then after cooling began to filter. Now I have this…. Stannous test shows gold so I guess I’ll drop my gold but why is it green? Copper? Is it from the die? Or maybe because all bottoms weren’t “clean”. Some of the gold parts stayed with the top. Is It true that tops have no base metals other than spreaders?

 

[Yggdrasil]

Hi folks. Quick question. What did I do wrong? Ha! I processed 100g of mixed BGA (copper top and no copper top). I mechanically separated top from bottom. I incinerated the tops. Stored the bottoms for “maybe one day”. I separated the copper heat spreaders and put the remaining ashes in my ball mill for 1/2 day. I left the die in there too. Once powder, I gravity separated with water and beakers until I had maybe 50ml of material left. I went straight to AR with a stir bar and heat of 80C. Stir bar and die pebbles probably not good for my beaker? Anywho, I added 150ml HCl (31.5%) and 32 drops of concentrated Nitric in two sets of 16 until reaction stopped. I added another 100ml HCl and another 8 drops of nitric just to ensure no reaction. Left the beaker cook for 10min between all steps. I added Sulfamic while still hot till no reaction. Pulled off heat and then after cooling began to filter. Now I have this…. Stannous test shows gold so I guess I’ll drop my gold but why is it green? Copper? Is it from the die? Or maybe because all bottoms weren’t “clean”. Some of the gold parts stayed with the top. Is It true that tops have no base metals other than spreaders?

What do you mean with copper top BGA?
Cpu with heat spreader?
The cloudyness may be any salt that may come out when cooling down.
No problem, it will filter well as long as it's not metastannic acid.
The green probably comes from dissolved copper.

Do you have pictures from the BGAs?

 

[AndrewSuperD]

Hey. Thanks for the quick response. I assumed the bgas had copper tops. These are gold corner bga. Picture attached.

 

[AndrewSuperD]

Also. I found some other issues. When I was pouring off my AR into the filter, there were bond wires not yet dissolved hiding in the crease of the beaker. How can I get all the gold dissolved when dealing with so much carbon ash? I thought a stir bar would help, and maybe it did, but should I have waited even though the reaction seemed to have stopped or is there a better way? Could pan it I guess. I’m giving it another cotton filter to get out that white cloudy stuff. CuCl(I)?

 

[Swissgoldrefiner]

Hi...
I didt tryed sulfamic...but with SMB usually i need to dilute the solution and let it overnight. It was cloudy befor adding the sulfamic?

 

[Yggdrasil]

I'm not totally understanding what you did or not did do.
How did you separate top and bottom?
How much material.

It seem the process was not finished, when you have little material the brown fumes don't always show up.
Put it back and try with more nitric to see if you can get it all into solution.
The cloudiness may also be because of lead sulfate after the sulfamic addition.

 

[AndrewSuperD]

I had 101g of tops only. I separated top from bottom with needle nose plyers. I’ll post a pic of my bottoms. Some separated cleanly and some didn’t. I think the picture will make sense. I have it another cotton filter and it cleared right up. It’s cold outside so the drop is slow but progressing.

With the remaining carbon and gold from the process that didn’t finish…1)HCl boil then decant and 2) made AR again. It’s currently filtering crystal clear and darkish yellow as I’m used to. I’ve not yet added Sulfamic. I’m going to see if It clouds when I add Sulfamic and let it cool.

Thanks for all the help folks.

 

[orvi]

Anywho, I added 150ml HCl (31.5%) and 32 drops of concentrated Nitric in two sets of 16 until reaction stopped. I added another 100ml HCl and another 8 drops of nitric just to ensure no reaction. Left the beaker cook for 10min between all steps.

I don´t want to say it wasn´t done allright, but 32 drops for me is quite a low ammount. Realizing good volume of the solution, side reactions of AR forming NOCl and Cl2 escaping from the vessel... With this kind and ammount of material, i will certainly used more HNO3 personally.
This could be the reason why you seen gold bonding wires even after treatment with AR.
To be sure, I personally add few portions of few mililiters and extend the boiling time for at least half hour to assure complete dissolution of anything that could be dissolved. At higher temperature, nitric decompose in excess of HCl quite quickly, and just minimal ammount of sulfamic acid is needed to kill the excess.

Also, be aware that not properly incinerated (to just ash) chips contain good ammount of carbon. And carbon can very effectively adsorb dissolved gold from the solution. Not in every conditions, but often.

As my refining partner once said, with properly incinerated chips, it is sufficient to shake them inside the plastic container and all you are left with are: slightly grey powdery ash, Si dies, legs and bonding wires. Bit exaggerated quote, but it follow the trend what is happening. Not all compositions of fillers in plastics are plain SiO2 and some tend to cake or clump at higher temperatures.

 

[FrugalRefiner]

Also, be aware that not properly incinerated (to just ash) chips contain good ammount of carbon. And carbon can very effectively adsorb dissolved gold from the solution. Not in every conditions, but often.

As my refining partner once said, with properly incinerated chips, it is sufficient to shake them inside the plastic container and all you are left with are: slightly grey powdery ash, Si dies, legs and bonding wires. Bit exaggerated quote, but it follow the trend what is happening. Not all compositions of fillers in plastics are plain SiO2 and some tend to cake or clump at higher temperatures.

I expect this is a problem in more cases than we know. If integrated circuits are not completely incinerated to ash, any remaining carbon could steal some of your gold and be thrown out with the trash.

Dave

 

[AndrewSuperD]

I don´t want to say it wasn´t done allright, but 32 drops for me is quite a low ammount. Realizing good volume of the solution, side reactions of AR forming NOCl and Cl2 escaping from the vessel... With this kind and ammount of material, i will certainly used more HNO3 personally.
This could be the reason why you seen gold bonding wires even after treatment with AR.
To be sure, I personally add few portions of few mililiters and extend the boiling time for at least half hour to assure complete dissolution of anything that could be dissolved. At higher temperature, nitric decompose in excess of HCl quite quickly, and just minimal ammount of sulfamic acid is needed to kill the excess.

Also, be aware that not properly incinerated (to just ash) chips contain good ammount of carbon. And carbon can very effectively adsorb dissolved gold from the solution. Not in every conditions, but often.

As my refining partner once said, with properly incinerated chips, it is sufficient to shake them inside the plastic container and all you are left with are: slightly grey powdery ash, Si dies, legs and bonding wires. Bit exaggerated quote, but it follow the trend what is happening. Not all compositions of fillers in plastics are plain SiO2 and some tend to cake or clump at higher temperatures.

Thank you very much for your response. I try to incinerate to white ash but admittedly, it doesn’t always get there. I will endeavor to ensure full white ash. I believe the carbon was so compact it was preventing AR from reaching the wires. Having said that, I will allow to “cook” longer. Thank you again for all the great information.

 

[orvi]

Thank you very much for your response. I try to incinerate to white ash but admittedly, it doesn’t always get there. I will endeavor to ensure full white ash. I believe the carbon was so compact it was preventing AR from reaching the wires. Having said that, I will allow to “cook” longer. Thank you again for all the great information.

Key point is oxygen. It must access the carbon somehow. And in the first place, it must be present you need oxidizing flame and good spreaded material. And good temperature to burn it. Or hot material and compressed air supply to burn it out - with simultaneous heating.
Just torching it inside the steel can is not good enough many times, as the oxygen cannot access the bottom layer of chips. You can clearly recognize it sometimes - top layer of chips is nice crispy white-grey coloured, and deeper you go in the layer, darker it gets.
You also can remove one chip and try to scrape through the ash. If it is more white on the outside than inside, you need to heat it and supply oxygen for longer You can comparatively place one chip on some steel mesh or firebrick, and hit it with torch to red heat, burn off all plastic and observe if it goes lighter in color if contact with oxygen is prolonged.

Good discussion about pyrolysis, types of flame and building a pyrolysis reactor was done here, just type keywords and you will find it.

 

[AndrewSuperD]

Key point is oxygen. It must access the carbon somehow. And in the first place, it must be present you need oxidizing flame and good spreaded material. And good temperature to burn it. Or hot material and compressed air supply to burn it out - with simultaneous heating.
Just torching it inside the steel can is not good enough many times, as the oxygen cannot access the bottom layer of chips. You can clearly recognize it sometimes - top layer of chips is nice crispy white-grey coloured, and deeper you go in the layer, darker it gets.
You also can remove one chip and try to scrape through the ash. If it is more white on the outside than inside, you need to heat it and supply oxygen for longer You can comparatively place one chip on some steel mesh or firebrick, and hit it with torch to red heat, burn off all plastic and observe if it goes lighter in color if contact with oxygen is prolonged.

Good discussion about pyrolysis, types of flame and building a pyrolysis reactor was done here, just type keywords and you will find it.

Thank you very much. I tend to burn my chips in small increments in a large melt dish and have recently started using an old dog water bowl. The metal expands and contracts causing the chips to shift rapidly at times. Not my favorite but it works. I turn the chips as I go. Until there’s no excess gas flame coming off any of the chips. Hope that makes sense. If I ever put them in the crucible/furnace, I’ll have to figure out how to oxygenate them.

 

[AndrewSuperD]

I got .82g of gold off the 101g of gold corner bga. Lower than I was expecting, but hey, I’m new at this. I did another batch of 37 little 1”x1” (roughly) non-gold corner bga chips from telecom T1 cards. It’s the bga on the right side of the pic attached. (Not the pinned chip also pictured) That whole process went great. I got another .51g from that. I combined the gold and melted the pictured bead below. Thanks as always for everyone’s help and invaluable information! The bead picture is of the bottom because there’s some oxidation or impurity making that surface not as shiny. I saw the oxidation or impurity moving around the surface of my bead when melting. All of my gold beads need to be refined. When I get 10g or so, I’ll refine. I’d like to try my hand at refining with a cupel maybe. Anywho, hope you enjoy the pictures.

 

[orvi]

Thank you very much. I tend to burn my chips in small increments in a large melt dish and have recently started using an old dog water bowl. The metal expands and contracts causing the chips to shift rapidly at times. Not my favorite but it works. I turn the chips as I go. Until there’s no excess gas flame coming off any of the chips. Hope that makes sense. If I ever put them in the crucible/furnace, I’ll have to figure out how to oxygenate them.

We used a muffle furnance to heat and properly incinerate the whole boards for assaying. Cut the material in smaller manageable pieces, wrapped it in stainless steel mesh and placed into the furnance, fixed at 500-600°C overnight. Air was allowed to slowly come from the bottom of the furnance to burn the material properly to just ash. And mesh was used to allow oxygen to get more easier to the more hidden places.

This technique is not applicable to much larger scale, as it initially produce awful lot of fumes. But for pyrolyzed material, it is very convenient as carbon could be burned in controlled way.
For easy and good processing of some materials, temperature control is quite a thing. This apply also to whole BGA chips, not top/bottom separated. When run in big lots and whole, caution should be taken not to exceed temperatures like 700 °C or higher. Fiberglass botom then start to soften (glass fibre) and entrapp the gold bonding wires inside. This is sometimes a big deal, slicing yield even to half - as the acid cannot acces gold entrapped in the glass. When running like 5 kg of BGAs, manual separation top/bottoms is very inconvenient.

It could happen when you heat the stuff in thing like big crucible or stainless bowl inside the furnance. This could lead to more of a pyrolysis than incineration, because access to oxygen in the bottom-enclosed vessel is low.
Then, conveniently, the steel tubing is passed to the bottom and air is passed through the material from the bottom. When this is done, leftover carbon start to burn - and it can go very very high with temperature. If not controlled and adjusted, easily over 1000 °C You could orient by the colour and intensity of glowing mass - there are plentiful tables on the internet about this.
Because of this i preffer burning in mesh bowls or "strainer-like" pots with smaller batches of ICs. Put it in the furnance, adjust gas to low, apply second afterburner to burn all fumes evolved. Let chips to burn on their own, and when all volatile matter burns (smoky flame goes away), retain the heat at low and slowly start to add air or use oxidizing flame torch till the stuff goes to crispy grey-white colour all the way down the vessel. This could take some time

 

[joekbit]

It's been a long time since I did any chips but, I used a steel coffee can. With the top and bottom removed I placed 1/4 inch steel screen inside the can. Then used a Colemen link below. Set the can on top, lots of air flow. I would water rinse the ash off. Anything not white went back into the burner. It works great. Interesting the link shows up saying robot or human for some reason. But it works


https://www.walmart.com/ip/Coleman-...Camping-Stove-with-Adjustable-Burner/20369794