joubjonn
Well-known member
Would appreciate any thoughts and feedback. Dissolving everything I would think is a good idea.
These are awesome but have no idea the most practical way to deplete these.
- Thread starter joubjonn
- Start date
Help Support Gold Refining Forum:
There may be less than you believe.
First you need to depopulate them.
Then the options would be copper chloride leach and refine the foils.
Lots of waste to treat after.
Sulfuric stripping cell, little waste but dangerous concentrated Sulfuric.
Iodine-Iodide leach, fast but may be expensive to set up.
Cyanide/ferro/ferri cyanide leach.
Fast and cheap but may be dangerous if done incorrectly.
Do some research and ask questions.
Martijn
Well-known member
Be very carefull touching that white thermal contact paste. It could be toxic.
Dissolving whole boards is generally very bad idea. That is one of primary headache-inducing type of threads that emerge here - "Hi, I put 20lb of boards in acid, now I don´t know what to do, gold isn´t in solution"
If you do not have dozens of pounds, depopulate them either mechanically or with heatgun. Then soak the boards in HCL with air bubbling through (AP) - base metals will slowly dissolve, leaving gold foils. Then you will fish out boards from the liquid, clean the foils off them and strain the solution to reclaim the foils.
More components you depopulate from boards, less acid you will spend = less toxic liquid waste you produce.
If you happen to have a whole bunch, then it would be harder to crack this one. Of yourse, AP could be scaled up, but it is nowhere nice to process pallet of boards for that little gold they contain. Most of the gold is ENIG - very thin plating. Even very generously (in terms of plated area) plated boards sometimes won´t have ammount to justify the work. In the photo, there are few hundred mg Au max.
If you have access to cheap nitric acid, you can use nitric acid to dissolve base metals instead of AP, leaving gold foils intact. This is the quick procedure.
If you are after easy money, you will be better selling them as they are to companies like Boardsort.
If you want to process bigger quantity of boards (hundreds of kilos), best would be to depopulate them (or go with whole boards even), then pyrolyze/incinerate and smelt. Obtained copper metal ingot with dissolved gold would be then processed electrolytically. But this is rather difficult process to tune it right - as tin and lead are your enemies
and you need to remove them upfront, preferrably pyrometallurgically. Need to have good incinerator setup and large furnance able to go past 1300°C to enable use of CaO flux for the fiberglass.Nice thing is - not very much liquid waste is generated through this process, and actual money-holding metal = copper is reclaimed in quite pure form to be sold for top dollar. And if you are feeling brave, you can reductively smelt the slag to obtain tin and lead contained, if you have means to sell it for the actual value, not bargain prices in scrapyards.
Very little gold there. I have found this type of material isn't really gold plated..... it's more or less a gold wash coat, for lack of a better term. The gold doesn't generally come off as a foil, but more like a black powder.
I have a bunch of this stuff too and I don't know what to do with yet.
I assume some of that is satellite equipment?
I have a bunch of this stuff too and I don't know what to do with yet.
I assume some of that is satellite equipment?
silversaddle1
Well-known member
Care to share some info on that?
Martijn
Well-known member
(edited to take out double text: "most are just zinc oxide but some can cantian")
so i Googled it.. From another forum (that looks just like the GRF lay-out b.t.w.):
How toxic is thermal paste and is there a safer version? - SPCR
(quote):
"Thermal greases use one or more different thermally conductive substances:
Ceramic-based thermal grease has generally good thermal conductivity and is usually composed of a ceramic powder suspended in a liquid or gelatinous silicone compound, which may be described as 'silicone paste' or 'silicone thermal compound'. The most commonly used ceramics and their thermal conductivities (in units of W/(m ·K)) are:[4] beryllium oxide (218), aluminum nitride (170), aluminum oxide (39), zinc oxide (21), and silicon dioxide (1). Thermal grease is usually white in colour since these ceramics are all white in powder form. These figures are for bulk material, not thermal grease.
Metal-based thermal grease contain solid metal particles (usually silver or aluminum). It has a better thermal conductivity[citation needed] and is more expensive than ceramic-based grease.
Metal-free thermal compound does not allow electrical conduction and therefore it eliminates the risk of short circuit and keeps the components safe. This type of thermal conductor is often used in computer systems to increase the thermal conductivity of the CPU or GPU. Besides, it is very easy to remove comparing with other types of thermal grease.[5]
Carbon based. There are products based on with carbon-based conductors, using diamond powder,[6][7][8] or short carbon fibers [1], they have the best thermal conductivity[citation needed] and are generally more expensive than metal-based thermal grease.
Liquid metal based. Some thermal pastes are made of liquid metal alloys of gallium. These are rare and expensive.
Phase Change Metal Alloy (PCMA) is not a "grease" but another type of Thermal interface material. The design consists of a sealed alloy metal pad that needs to be "reflowed" under high heat (typically 90-100C.) The alloy on the inside of the seal will change phases, and fill all the micro-voids. Since this material is made of mostly metal alloy, the thermal properties of this interface material are very good.
All but the last classification of compound usually use silicone grease as a medium, a heat conductor in itself, though some manufacturers prefer use of fractions of mineral oil.[citation needed]
All these compounds conduct heat far better than air, but far worse than metal. They are intended to fill gaps that would otherwise hold air, not to create a layer between component and heatsink—this will decrease the effectiveness of the heatsink. Ideally perfectly smooth and flat metallic surfaces would not need heatsink compound." (end quote)
So silicone paste with zinc oxide are not the worst of materials, but beryllium oxide is definitely not. Looking at its thermal conductivity, i think it will be the No 1 choice for high end industrial applications.
Not knowing what the manufacturer used, i would go for safe and use gloves. As far as other components in the paste, I always do: "Copy / Paste + MSDS" but it's a wide range of products and you never know for sure. I don't think it will pop up on the parts list.
Better to be safe than sorry.
Martijn.
i learned that at school thirty years ago.
so i Googled it.. From another forum (that looks just like the GRF lay-out b.t.w.):
How toxic is thermal paste and is there a safer version? - SPCR
(quote):
"Thermal greases use one or more different thermally conductive substances:
Ceramic-based thermal grease has generally good thermal conductivity and is usually composed of a ceramic powder suspended in a liquid or gelatinous silicone compound, which may be described as 'silicone paste' or 'silicone thermal compound'. The most commonly used ceramics and their thermal conductivities (in units of W/(m ·K)) are:[4] beryllium oxide (218), aluminum nitride (170), aluminum oxide (39), zinc oxide (21), and silicon dioxide (1). Thermal grease is usually white in colour since these ceramics are all white in powder form. These figures are for bulk material, not thermal grease.
Metal-based thermal grease contain solid metal particles (usually silver or aluminum). It has a better thermal conductivity[citation needed] and is more expensive than ceramic-based grease.
Metal-free thermal compound does not allow electrical conduction and therefore it eliminates the risk of short circuit and keeps the components safe. This type of thermal conductor is often used in computer systems to increase the thermal conductivity of the CPU or GPU. Besides, it is very easy to remove comparing with other types of thermal grease.[5]
Carbon based. There are products based on with carbon-based conductors, using diamond powder,[6][7][8] or short carbon fibers [1], they have the best thermal conductivity[citation needed] and are generally more expensive than metal-based thermal grease.
Liquid metal based. Some thermal pastes are made of liquid metal alloys of gallium. These are rare and expensive.
Phase Change Metal Alloy (PCMA) is not a "grease" but another type of Thermal interface material. The design consists of a sealed alloy metal pad that needs to be "reflowed" under high heat (typically 90-100C.) The alloy on the inside of the seal will change phases, and fill all the micro-voids. Since this material is made of mostly metal alloy, the thermal properties of this interface material are very good.
All but the last classification of compound usually use silicone grease as a medium, a heat conductor in itself, though some manufacturers prefer use of fractions of mineral oil.[citation needed]
All these compounds conduct heat far better than air, but far worse than metal. They are intended to fill gaps that would otherwise hold air, not to create a layer between component and heatsink—this will decrease the effectiveness of the heatsink. Ideally perfectly smooth and flat metallic surfaces would not need heatsink compound." (end quote)
So silicone paste with zinc oxide are not the worst of materials, but beryllium oxide is definitely not. Looking at its thermal conductivity, i think it will be the No 1 choice for high end industrial applications.
Not knowing what the manufacturer used, i would go for safe and use gloves. As far as other components in the paste, I always do: "Copy / Paste + MSDS" but it's a wide range of products and you never know for sure. I don't think it will pop up on the parts list.
Better to be safe than sorry.
Martijn.
joubjonn
Well-known member
Thanks guys. Haven’t refined yet. I just bought a propane foundry. Think I’ll try and use that to get a button and then go from there.
Fortunately, beryllium oxide has very low aqueous solubility. In the paste, it's less dangerous than as powder. The big risk is getting it wiped on something you'll eat later! You won't even notice, since it has a sweet taste... and I think we can all figure out how scientists of olden days found that out. They weren't the brightest sometimes.
rickbb
Well-known member
I would depopulate with a heat gun and a putty knife.
Then soak in Hcl to dissolve all the remaining solder. (This step is important, too much tin solder dissolved in the AP solution makes a huge mess that's hard to fix. And will tie up any dissolved gold in it.)
Rinse then chop up to smallish bits, (an inch or so), and soak in AP for days to weeks, depending on how fast it works, no real rush, just let it work.
Rinse through a sieve to remove the bigger bits.
Let settle and syphon off the liquid, and then start with either poor man's AR or Hcl/bleach process.
Same process as all my plated circuit boards, I save them up until I have a big enough batch to bother with. Chem cost is low, time cost is high, but I have way more time than money.
Then soak in Hcl to dissolve all the remaining solder. (This step is important, too much tin solder dissolved in the AP solution makes a huge mess that's hard to fix. And will tie up any dissolved gold in it.)
Rinse then chop up to smallish bits, (an inch or so), and soak in AP for days to weeks, depending on how fast it works, no real rush, just let it work.
Rinse through a sieve to remove the bigger bits.
Let settle and syphon off the liquid, and then start with either poor man's AR or Hcl/bleach process.
Same process as all my plated circuit boards, I save them up until I have a big enough batch to bother with. Chem cost is low, time cost is high, but I have way more time than money.
eightyeightysix
New member
Those boards manufactured in 2010/2011. Price of gold had already blown out to over 1.5k/toz. Either the cost of equipment was exponentially higher or the gold was exponentially reduced in manufacture. I have some boards like this - but they are circa 2000. One question that keeps going through my mind is - WHAT is the material and RF advantage to gold plating boards in a microwave/rf setting? Some of my radios were $5-7k each retail back in 2000. In 2000 gold was $274/toz. My guess is - to help reduce interference and crosstalk. How much would be needed to make a material impact? Answer could also be - to simply help prevent corrosion - as these radios are often placed in inhospitable locations. Anyone else have a thought on that?
nickrpotts
Member
Could you answer some questions.
Firstly how many of the circuits do you have?
The reason I ask is in the pictures you have shown, they appear to be made of different base materials, which with this technology normally changes the surface finish (the amount and method of how the gold is plated to the copper traces).
In my opinion Picture 1A1EBD*** is likely to be made of FR4 (as per traditional PCB). Detail states 700MHz so this is likely Enig (electroless nickel, immersion gold) Probably 3-5um nickel, 0.05-0.2um gold.
Picture 2 C12D2** looks as if it is a circuit made of Rogers 4003 or similar (this is a glass reinforced hydrocarbon material) bonded on to a metal carrier. Can you confirm if this feels heavy? If so probably copper? Or relatively lightweight? Probably aluminium. I think the mid/dark grey we are seeing is a silver loaded epoxy sheet, used to conductively bond the circuit to the carrier. If you scratch this does peel/flake off?
Picture 3 F658E** looks as if it is the back of a carrier plate, how heavy is it? copper or aluminium? You can see that the holes are threaded which typically isn't/cannot be done on the standard PCB FR4 material. On the other side is the circuit counter sunk?
Picture 4 069CC** looks as if it is a PCB bonded to metal carrier plates, no idea of circuit material as don't see the colour, are these heavy or light in weight? Copper or aluminium were standard material choices in 2010.
Picture 5 B3FE4** looks as if it is PCB made of Rogers 3003 or similar (ceramic filled ptfe). Is there a part number on the circuit pattern anywhere? As it may indicate the frequency which will help determine chosen surface finish if you have no access to XRF.
Now explanation to my questions.
Picture 1 likely to be thin gold plate. What is known as Enig (3-5um Ni, 0.05-0.2um Au). This is likely to have been carried out at the very end after the solder mask (green ink) was applied.
Picture 2 likely to have Enig to the PCB. Depending on the metal carrier the plating could vary. If aluminium Enig could be used, however if copper probably electrolytic pure gold <1um but likely thicker than the Enig, but probably no nickel plate. Plus there is silver loaded epoxy present, however minimal if any reclaimable silver.
Picture 3 could be the same as picture 2 impossible to tell from the image.
Picture 4 likely to be the same as picture 2.
Picture 5 could be Enig, Enipig (electroless nickel, electroless palladium, immersion gold), or it could be electrolytic nickel electrolytic gold this will be thicker gold thickness up to 5um. The plating whichever method was applied before the solder mask was applied, as these are solder dams to stop the solder flowing up the traces during assembly.
Do you have access to a PCB manufacturer who has XRF, for PCB this tends to be set up to measure the plating thicknesses on the circuit, as opposed to precious metal %. If so this will give you a much better idea as to whether the circuits are worth you processing yourself and by which method.
My suggestion would be to depopulate to remove all components.
Then dependant on quantities of PCB's place on a hot plate heat to around 300'c and remove the carrier plate/plates from the PCB. They should start to separate themselves (needs doing with fume extraction as fumes can be hazardous).
Then you can process the carrier plates and PCB's. There will be multiple options as to how to proceed depending on your set up and expertise.
