New feedstock question

[Golden]

Hello All,
New member here. I have been in the industry for several years, but am only an expert on the 2 feedstocks I currently process. A gold plated Nickel waste product and a gold plated copper bare circuit board without masking.

I have just been offered several tons of a fully populated and used circuitboard that was manufactured between 1979-1983. All traces are gold plated, but has appropriate solder masks. Chip wise there are .33 lbs of plastic IC chips and .1 ceramic chips. Only trash on the board are 2 ferrous switches. Breaking open a bunch of ICs, all ceramics are gold inside, wires and silicon base. The plastics are not gold. Maybe palladium, have not confirmed.

My question for the forum is this. I'm not use to dealing with all the additional trash tin, lead, silver etc. no clue how to handle it. However, is it worth to try and setup a system for this? I cannot sell them as they must be provided a certificate of destruction. They currently have quite the backlog but looks like they would generate a few hundred pounds a week overlooking the stockpile. I suspect this would only last a year or two. These boards are coming from a telecom military contract.

While I have a full lab, I'm only currently positioned to do actual production with an I guess you refer to it here as an electro-winning cell, and a halide recovery circuit.

I made an attempt to process a few boards the other day, and it was quite laughable. Not sure I have ever felt so dumb.

I'm concerned about all the new toxic material I'd have to learn about in old chips. I'm concerned that this is a distraction to my existing expertise. But, if I'm being honest, I'm bored and willing to learn something new and even spend money setting up a new line if it makes financial sense.

Thank you for listening. Don't burn me too bad
-G

 

[eaglekeeper]

I cannot sell them as they must be provided a certificate of destruction.

What level of destruction do they require.

 

[4metals]

Golden, dumb is when you jump in with 2 feet and end up with hundreds of pounds of half processed scrap and more waste than you can handle. What you are doing is smart.

What I guess you are currently doing from your bare bones description is reverse plating or chemically stripping parts and selectively dissolving the values so you don't end up with a lot of metals dissolved in solution and a major waste headache. And from the sound of it you are concentrating the values and shipping them forward to a refiner to generate refined metals. The 2 types of waste you currently process have 100% of the values exposed to your process chemistry.

POP.... that's the sound of the bubble bursting if you think this new feedstock will be as easy. The main culprit will be layered values and getting your chemistry to meet your values.

But let's start simple. Currently are you stripping with a cyanide based strip? And plating the gold out of the strip with a electrowinning style device?

 

[Golden]

What level of destruction do they require.

That's a fair question. I don't have specifics, but I am assuming absolutely nothing able to be reverse engineered or any identifiable markings (silkscreen on boards, or markings on chips).

 

[Golden]

Golden, dumb is when you jump in with 2 feet and end up with hundreds of pounds of half processed scrap and more waste than you can handle. What you are doing is smart.

What I guess you are currently doing from your bare bones description is reverse plating or chemically stripping parts and selectively dissolving the values so you don't end up with a lot of metals dissolved in solution and a major waste headache. And from the sound of it you are concentrating the values and shipping them forward to a refiner to generate refined metals. The 2 types of waste you currently process have 100% of the values exposed to your process chemistry.

POP.... that's the sound of the bubble bursting if you think this new feedstock will be as easy. The main culprit will be layered values and getting your chemistry to meet your values.

But let's start simple. Currently are you stripping with a cyanide based strip? And plating the gold out of the strip with a electrowinning style device?

lol yeah I've been thinking my little bubble is popping. I cannot understate how dumb I felt when I tried a practice run the other day. and yes you are correct, that is basically how I'm processing my current stock. I mean, I thought I knew what I was doing, but I forgot the most basic steps ended up with a silver chloride mess ... it was amateur hour.

I don't want to say no, long time client, new management, don't want to lose what I have. But truly I have no idea how to process dirty products at scale. I mean, sure, we can all do a single batch. But how do you do this at scale and make money? The only good news I have to offer is. All of the boards are exactly the same. So in the event I can come up with an SOP it should work for everything that comes in the door.

 

[4metals]

A few simple tests on a few pieces of this feedstock can really tell us a lot. First if you took an entire circuit and stripped it using your current methods, it will be inefficient as hell but do you think you will recover 50% of the value?

Second if you shredded and granulated a board and exposed it to the same chemistry would the yield jump to 75%?

I have clients that can get all the way to +80% recovery on some feeds and they do what they can efficiently and ship the "residue" the rinsed and dried remnants off to a refiner set up to process it completely. In your case the product would be destroyed going out the door. And it would be quite homogeneous which benefits you because you know what to expect as a return. This can be especially beneficial if your circuit doesn't currently get all of the PM's.

What are you using to dissolve gold, the silver chloride in your response says it may not be cyanide? And what type of analytical instruments are in your lab? An Atomic Absorption possibly?

 

[Golden]

A few simple tests on a few pieces of this feedstock can really tell us a lot. First if you took an entire circuit and stripped it using your current methods, it will be inefficient as hell but do you think you will recover 50% of the value?

Second if you shredded and granulated a board and exposed it to the same chemistry would the yield jump to 75%?

I have clients that can get all the way to +80% recovery on some feeds and they do what they can efficiently and ship the "residue" the rinsed and dried remnants off to a refiner set up to process it completely. In your case the product would be destroyed going out the door. And it would be quite homogeneous which benefits you because you know what to expect as a return. This can be especially beneficial if your circuit doesn't currently get all of the PM's.

What are you using to dissolve gold, the silver chloride in your response says it may not be cyanide? And what type of analytical instruments are in your lab? An Atomic Absorption possibly?

Actually thats brilliant. So I can take the new feedstock just by setting up a grinding line. Their destruction requirements are met. I have plenty of room to stockpile bag lined gaylords of shredded circuits. I can run all kinds of tests to see if I want to process it completely or partially or even sell them off shredded. I like it.

Right now I would be concerned just dropping a board into our current process as I have no idea what all complexes it would create and no idea how to clean up the waste to be able to discharge. Last week I took half of a board and dropped it into an AR mix with no pre-treatment. I took the other half and dropped it into an AP mix with no pre-treatment. Having no prior experience with AP. Both went about as well as you'd imagine. The tin totally blew up the AR mix, and I'm not sure what all went wrong in the AP. Running numbers I'm not sure it makes sense to pre-treat with nitric however. So how do you guys do this and make money?

Lab wise, pretty standard stuff. We have an old perkins AAS used primarily for discharge tests ... we test everything beforehand, obviously. Neighbors have a mass spec that I have access to but not sure that really helps in this case lol. Only really interesting equipment is we have some of those siemens air quality sensors.

 

[kurtak]

Picture of your new feed stock would be good in order to see just what all is on the boards

Edit to add; - What the boards look like can make a difference on best path forward

Kurt

 

[Brett Novak]

are the boards single or double sided? or are there multiple layers in the sandwhich? If they are single or top and bottom layer only (common with older boards and test boards) then the easy way to strip them is start with hot water and LYE solution - this will remove the green solder mask / epoxy. I then do an AP soak for a while (weeks), then wash all the boards in clean water. some scrubbing will usually remove all of the gold trace, then it's into AP for the muck at the bottom. The boards themselves usually don't go into AP since the inner layers are only copper.

 

[lazersteve]

Brett the process you outline above works well for removing the solder mask on most boards. Anyone looking for more information on this can use the forum or my custom Google search post for the term "solder mask" . Lots of good information.

Side note: boards with "conformal coatings" are exceptionally difficult to clean and other techniques are more appropriate. These coatings are found in the aviation, military, aerospace, automotive, and some medical appliances boards. Confomal coatings tend to be applied over all components on the boards, not just over the areas with traces around the components on the boards. These coatings can be clear, pink, black, gray, and maroon typically. I'll dig up some photos later.

Steve

 

[4metals]

Right now I would be concerned just dropping a board into our current process as I have no idea what all complexes it would create and no idea how to clean up the waste to be able to discharge.

And the gorilla in the room is your current process. One thing you may not realize at this point as a new member is the wide variety of expertise that exists on this forum. But the more we know about the process the more we can help you. We are all quite willing to help you through this. Even more so since you have analytics to back it up.

I understand your hesitancy to tell us too much about your process, but remember, you came to us not visa versa.

 

[Golden]

Picture of your new feed stock would be good in order to see just what all is on the boards

Edit to add; - What the boards look like can make a difference on best path forward

Kurt

Totally understand. I am having someone clean the photos to post. I have to comply with client requirements by removing all markings etc. Give me a few and I will show you what I'm dealing with.

 

[4metals]

Pictures can tell us a lot but I completely understand your discretion. Like I said you will receive a lot of valuable information here to help you that you will not get anywhere else.

 

[Golden]

And the gorilla in the room is your current process. One thing you may not realize at this point as a new member is the wide variety of expertise that exists on this forum. But the more we know about the process the more we can help you. We are all quite willing to help you through this. Even more so since you have analytics to back it up.

I understand your hesitancy to tell us too much about your process, but remember, you came to us not visa versa.

Fair. I'm not use to this kind of community so forgive me. I always worry about someone stepping up and eating my lunch. I love life and don't want it to change.

But here you go. Keep in mind, I make zero claims that this is the best or most efficient or any such thing. This is simply the process I understand well and was able to get permitted as I am within city limits in the US. Current setup is totally simple.

Feedstock 1: unmasked gold-plated circuit boards, unpopulated.
step 1, grease/oil removal .. client stacks this waste in a very bad location. What we wash it with changes based on price, but just your standard degreaser vat followed by a city water wash.
step 2, material is placed inside a cyanide circuit for a very specific time. About 2 hours (thick plating). It is rinsed and stacked to be sent to refiner for nickel/copper content.
step 3, after about a week the cyanide solution is loaded. PH is adjusted and it goes into our electrowinning circuit. From there gold goes into our refining phase which is lab based AR, normal process, nothing special.
step 4, depending on how things test, it is either discharged or put back in circuit. We run everything through a resin tank and activated charcoal just in case we mess something up, but, that is overkill. I have never collected a single gram from the carbon in over 5 years.

Feedstock 2: coils of gold plated nickel copper.
(this is going to generate so much hate) just understand this is based on cost and permits.
step 1. Material is dropped into a KI tank for about 15 minutes.
step 2. city water rinse.
step 3. material stacked for refiner for nickel/copper content.
When KI tank is fully pregnant. PH adjustments to drop the I and the Au. I is reused obviously. Au goes to AR lab refinement.
Every once in a while we do get loaded with Ni not entirely sure why, but it happens. We adjust our electrowinning circuit and plate it out, then return the lixiviant to the circuit.

Thats it. That is all I know. Anything beyond that, I'm clueless.

 

[Golden]

Fair. I'm not use to this kind of community so forgive me. I always worry about someone stepping up and eating my lunch. I love life and don't want it to change.

But here you go. Keep in mind, I make zero claims that this is the best or most efficient or any such thing. This is simply the process I understand well and was able to get permitted as I am within city limits in the US. Current setup is totally simple.

Feedstock 1: unmasked gold-plated circuit boards, unpopulated.
step 1, grease/oil removal .. client stacks this waste in a very bad location. What we wash it with changes based on price, but just your standard degreaser vat followed by a city water wash.
step 2, material is placed inside a cyanide circuit for a very specific time. About 2 hours (thick plating). It is rinsed and stacked to be sent to refiner for nickel/copper content.
step 3, after about a week the cyanide solution is loaded. PH is adjusted and it goes into our electrowinning circuit. From there gold goes into our refining phase which is lab based AR, normal process, nothing special.
step 4, depending on how things test, it is either discharged or put back in circuit. We run everything through a resin tank and activated charcoal just in case we mess something up, but, that is overkill. I have never collected a single gram from the carbon in over 5 years.

Feedstock 2: coils of gold plated nickel copper.
(this is going to generate so much hate) just understand this is based on cost and permits.
step 1. Material is dropped into a KI tank for about 15 minutes.
step 2. city water rinse.
step 3. material stacked for refiner for nickel/copper content.
When KI tank is fully pregnant. PH adjustments to drop the I and the Au. I is reused obviously. Au goes to AR lab refinement.
Every once in a while we do get loaded with Ni not entirely sure why, but it happens. We adjust our electrowinning circuit and plate it out, then return the lixiviant to the circuit.

Thats it. That is all I know. Anything beyond that, I'm clueless.

I should also say, that our final AR process, we use butyl diglyme. Not sure if that is normal in these parts, but it got us to 5 9s.

 

[Golden]

Brett the process you outline above works well for removing the solder mask on most boards. Anyone looking for more information on this can use the forum or my custom Google search post for the term "solder mask" . Lots of good information.

Side note: boards with "conformal coatings" are exceptionally difficult to clean and other techniques are more appropriate. These coatings are found in the aviation, military, aerospace, automotive, and some medical appliances boards. Confomal coatings tend to be applied over all components on the boards, not just over the areas with traces around the components on the boards. These coatings can be clear, pink, black, gray, and maroon typically. I'll dig up some photos later.

Steve

Jesus, reading that is scary. the good news is I have none of that. I just have a solder mask over the gold->nickel->copper plating.

 

[4metals]

Thats it. That is all I know. Anything beyond that, I'm clueless.

You can't make that claim if you do this!

I should also say, that our final AR process, we use butyl diglyme. Not sure if that is normal in these parts, but it got us to 5 9s.

So your basic CN strip circuit you strip in either a proprietary strip or basic KCN and then run it through something like this?

When the copper cathodes load up you dissolve them in AR?
That seems to be an effective method as long as you don't have to account for small lots routinely.

KI doesn't bother me, I use to strip drums of hybrid thick film ceramics in KI. Great process, easy recovery.

I don't know why the process you use on the boards (CN and electrowinning) cannot be used to strip the coils of gold plated material as well.

Anyway let some of our members who specialize in circuitry chime in after you post some photos.

 

[nickvc]

The reason you get loaded with nickel is because cyanide will preferentially dissolve nickel over the gold once exposed the same is true of copper, you can reduce this problem by having less free cyanide in your solution which of course slows down the processing, as was pointed out by a very wise processor there’s always a trade off with processing .
You could try pumping your solution around the product so the solution is covering all the product with fresh solution all the time this should reduce the stripping time , the other alternative is to load the product into a rotating drum and move the product again exposing all the product to the solution.
With cyanide processing it’s almost impossible to recover all the values so I hope your end refiner pays on any gold as well.

 

[nickvc]

As an aside you can easily find out if you have gold in your waste by taking a small sample from several different batches and melting into an ingot an either get an assay or an xrf reading from a decent properly set up machine.

 

[kurtak]

are the boards single or double sided? or are there multiple layers in the sandwhich? If they are single or top and bottom layer only (common with older boards and test boards) then the easy way to strip them is start with hot water and LYE solution - this will remove the green solder mask / epoxy. I then do an AP soak for a while (weeks), then wash all the boards in clean water. some scrubbing will usually remove all of the gold trace, then it's into AP for the muck at the bottom. The boards themselves usually don't go into AP since the inner layers are only copper.

Brett - Per the bold print - this process may well work (or work well) for the back yard hobby refiner that is dealing with smaller amounts of boards (10 - 20 - 50 pounds of boards) that does not care how long it takes to get their gold out of the feed stock (boards)

Hobby refiners generally don't care if they make a profit (or not) &/or how long the process takes --- it's a hobby

But it most certainly won't work for a larger scale commercial refiner that is taking in larger amounts of boards & doing so on a regular/continuing basis

Large scale operators (actual businesses) need to see their returns in a timely manner (ASAP) not only so they can pay their supplier/client in a timely manner but also see a consistent & dependable cash flow that pays for cost of operations

There is a reason that the BIG BOYS don't use your suggested process - they would go broke in short order

The OP of this thread is not a hobby refiner --- he is a commercial business so needs methods that will process continuing large amount of boards in a timely manner --- AP is not that process

Kurt