# Gold on pcb



## Jbroadway (Oct 16, 2016)

Hi all I'm not sure if this is in right place but I have got some pcbs and they have gold traces and I am wondering how everyone goes about processing them







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## bemate (Oct 16, 2016)

I have quite a few of those myself, but I thought the gold-tone was copper rather than gold... Seeing as they serve no obvious function towards signalling, it wouldn't make sense to have gold there. And considering how skimpy they are with the gold elsewhere in the electronic parts, I would think that is not gold. I hope I'm wrong though... :wink:


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## anachronism (Oct 16, 2016)

The components under the black "blobs" are more likely to contain gold than the traces on that type of board. Soaking the boards in NaOH is one way to remove the green solder mask but I would recommend that you look up the dangers of working with that stuff before you do it and ensure that you follow the relevant safety precautions because it is extremely unforgiving if you get it in your eyes.

Edit: Yes there are certain types of board that gold plated traces under the solder mask, removing the mask completely will help you determine that. One thing of note- differing revisions of the same types of boards can vary a lot.


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## Jbroadway (Oct 16, 2016)

I would agree but knowing that This stuff is out of high end electronics it wouldn't surprise me, I have seen copper traces and they are nowhere near this shiny... as of yet I don't actually have any gold testing kits or chemicals to prove it and was wondering if anyone had this experience


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## Jbroadway (Oct 16, 2016)

anachronism said:


> The components under the black "blobs" are more likely to contain gold than the traces on that type of board. Soaking the boards in NaOH is one way to remove the green solder mask but I would recommend that you look up the dangers of working with that stuff before you do it and ensure that you follow the relevant safety precautions because it is extremely unforgiving if you get it in your eyes.



Thanks anachronism I would follow all safety precautions and I was wondering if I could get the green mask off thank you 

Any idea on getting rid of the black blobs??

I pmed you the other day 


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## anachronism (Oct 16, 2016)

Ahh I hadn't checked my PMs- thanks I'll go take a look. 

Those black blobs are processed in a very similar manner to the BGA and north bridge chips- there's a whole load of resource on the forum with regards to processing those if you look around.


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## Jbroadway (Oct 16, 2016)

it's just know what to search for thank you, should I remove them from the boards?


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## anachronism (Oct 16, 2016)

Sure if you bend the boards they very often pop off as they can be extremely brittle.


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## Jbroadway (Oct 16, 2016)

Spot on







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## anachronism (Oct 16, 2016)

There you go. Oh look - gold


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## kurtak (Oct 16, 2016)

anachronism said:


> There you go. Oh look - gold



& its not just the gold plating under the blob (on the board) but for every trace on the board going to the blob there is a gold bonding wire "in" the blob which then connects to the IC chip in the blob

Kurt


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## kernels (Oct 16, 2016)

Yeah, so, no-one is really saying this loudly and clearly, there is almost NO gold on that PCB, it is a gold 'flash' coating over the pads to prevent corrosion before the PCB is assembled. They are pretty much not worth processing.

The gold in you boards is located inside the black blobs in the form of bond wires.


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## g_axelsson (Oct 16, 2016)

Copper traces with gold flash on exposed surfaces. It's called ENIG, do a search. It is used for oxidation protection before soldering and is a lot thinner than gold fingers.

http://goldrefiningforum.com/phpBB3/viewtopic.php?f=34&t=21751#p225672

Göran


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## Jbroadway (Oct 16, 2016)

Is it worth processing this flashing or isn't it worthit


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## anachronism (Oct 16, 2016)

That really depends on how much of it you have. Any gold that will give you a visible result is a good learning tool. If you have only a few of these boards then the answer is probably no from a financial perspective but as a learning excercise- maybe.


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## g_axelsson (Oct 16, 2016)

I agree with anachronism, It depends...

What quantity, which process, what are your labor costs... and so on.

It isn't easy to get it either, most of the gold flash is dissolved in the solder and the unsoldered part you see is so thin it breaks down to microscopic flakes if you dissolve the trace under it.

For me it isn't worth processing it myself, but I toss it in the box for cards that I'm sending out once I have enough to get paid for the content and not a flat rate.

Power supplies and brown boards (old TV boards, radios...) goes into the cards I sell to the local scrap yard for a pittance.

Göran


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## Jbroadway (Oct 16, 2016)

Thanks for all of the input, I think for the learning process I will cut off anything that is exposed and use that and the cards can be boxed 

Now for learning the processes 


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## kernels (Oct 17, 2016)

For learning, you are far better to go on ebay and spend too much money for some RAM or trimmed fingers. It doesn't matter if you pay too much, because at least you will end up with enough gold that you can actually see it drop out of solution and melt it into a (small) button.

By processing a few of those LCD boards, you may not even have enough gold to see it drop out of solution and almost certainly not enough to make melting it worthwhile.

Same thing basically applies to those bond-wire-blobs. You want at least 100g or so of them before you are likely to end up with around 0.1g to 0.3g of gold.


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## patnor1011 (Oct 17, 2016)

These black "blobs" will run much more than BGA IC.


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## Jbroadway (Oct 18, 2016)

kernels said:


> For learning, you are far better to go on ebay and spend too much money for some RAM or trimmed fingers. It doesn't matter if you pay too much, because at least you will end up with enough gold that you can actually see it drop out of solution and melt it into a (small) button.
> 
> By processing a few of those LCD boards, you may not even have enough gold to see it drop out of solution and almost certainly not enough to make melting it worthwhile.
> 
> Same thing basically applies to those bond-wire-blobs. You want at least 100g or so of them before you are likely to end up with around 0.1g to 0.3g of gold.



Thanks kernels

I have just trimmed a box of ram for its fingers so have them (though I would like more) I was actually thinking of removing the blobs and trimming all exposed gold off the boards and chuck that into the finger mix would that be a bad idea??



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## kernels (Oct 18, 2016)

Jbroadway said:


> kernels said:
> 
> 
> > For learning, you are far better to go on ebay and spend too much money for some RAM or trimmed fingers. It doesn't matter if you pay too much, because at least you will end up with enough gold that you can actually see it drop out of solution and melt it into a (small) button.
> ...



No problem throwing any bits of PCB with visible gold into AP with the fingers, they are essentially the same thing, just with a thinner gold plating. Make sure you have an aquarium air pump bubbling air though your AP, you can also use an aquarium heater (set at about 30 deg C) if the temperature is cold in your part of the world, it will greatly speed up the process. Make sure only the glass part of the heater is sitting in the solution.

I usually try not to mix gold flash boards with cut fingers if the boards still have some solder on them. In theory it should not matter, but I like running 'clean' AP batches and 'dirty' AP batches.


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## kernels (Oct 18, 2016)

patnor1011 said:


> These black "blobs" will run much more than BGA IC.



Yeah, good point, those black blobs could be around 1g+ per 100g since they have a better overall mass to gold ratio than a standard BGA. Good spotting there patnor1011


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## Jbroadway (Oct 18, 2016)

Do I need to use any special air lines or will silicone tubing be ok?? 


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## kernels (Oct 18, 2016)

I've never had a problem with aquarium air line tube


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## Jbroadway (Oct 19, 2016)

Can you mix ap with water to get the aquarium heater covered?


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## kernels (Oct 19, 2016)

Try to use as little AP solution as possible, makes filtering and clean-up much quicker. Lay the heater sideways if need be, only the bottom part with the heating coil needs to be in the liquid. I just bought the smallest heater available, only has about 2 inches in the liquid. 

I would be inclined to add more HCl to increase my AP level, rather than dilute with water.


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## Jbroadway (Oct 19, 2016)

Thanks that's really helpful advice, can I ask do you process plated pins the same way? Even ones that are magnetic? I read something somewhere about it but can't find it now...


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## kernels (Oct 19, 2016)

Jbroadway said:


> Thanks that's really helpful advice, can I ask do you process plated pins the same way? Even ones that are magnetic? I read something somewhere about it but can't find it now...
> 
> 
> Sent from my iPhone using Tapatalk



In theory you can use AP to dissolve the base metals out of the non-magnetic (copper based) plated pins, there is a user on here (Tzoax) who has a thread where he does it, but really, you are dissolving away a massive amount of base metal for a small amount of gold.

If you have a large quantity of plated pins, you want to investigate a cyanide type leach (dangerous) or a reverse-electroplating Sulfuric Acid Cell (dangerous). Both of these solutions act on the gold, rather than the base metal.


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## Jbroadway (Oct 20, 2016)

I think I'll stick to the slower less dangerous one for now  learn that and get that working right


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## Elektrikis (Nov 8, 2016)

g_axelsson said:


> Copper traces with gold flash on exposed surfaces. It's called ENIG, do a search. It is used for oxidation protection before soldering and is a lot thinner than gold fingers.
> 
> http://goldrefiningforum.com/phpBB3/viewtopic.php?f=34&t=21751#p225672
> 
> Göran



You are right. 

https://www.youtube.com/watch?v=HIYbrFuxBgo


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## clearsteam (Nov 8, 2016)

I think this is useful, a seminar from the industry, whilst most of the "golden" cards that we come across are enig --(2 to 4 micro inches thick) some will be electrolytic gold/hard gold (25 to 40 micro-inches thick) and possibly more on cards where gold has been used as etch resist (rare high end industrial applications often with metal substrate ) http://www.epectec.com/downloads/surface-finishes.pdf


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