# Full Gold tracks?



## goldmelts (Jul 5, 2008)

HI all,

I have stumbled onto something very interested.

Attached is a picture of some Compaq SCA-to-Backplane harddrive PCBs.
- The top is the same card, but no gold under greenplastic
- The middle one is an untouched one (OK, after cutting fingers, and removnig SCA connector)
- The bottom is a scrapped one

Firstly I see gold fingers so I give them a quick snip, and add them to the pile. Then I notice that the grounding screw holes are also gold. 

I start scraping, and the tracks under the green plastic are gold too.
First I start gentle to not damaged the gold plating, then harder, and harder, and harder.

I Sh*t you not, I'm scraping away like hell, and none of the gold plating is showing copper underneath!!!! :shock: 

Can the tracks be full gold?

Now it's not perfectly clean of green plastic, but I'm assuming that once I dissolve the gold foil/tracks with HCL-CL the plastic bits will fall off.


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## lazersteve (Jul 5, 2008)

Before you jump for joy, peel one of the traces and drop it in a small mix of AP (10 mL 2arts HCl, 1 part proxide). In 10-15 minutes you should see a blue to green color forming proving copper. I have seen lots of gold plated traces on PCBs, but never have I seen pure gold traces.

Steve


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## flankdrive04 (Jul 5, 2008)

If the tracks are indeed Gold Plated, then how much damage are you doing by scraping of the solder mask? Is there a chemical that removes solder mask quickly and easily??

Cheers!


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## goldmelts (Jul 5, 2008)

Lazersteve,

I'm positive the are not solid gold. But I did noticed they are not thinly gold plated like some other stuff I have seen.


flankdrive04,

Now regarding removing the solder mask, I don't know an easy way to remove it. I can say that I could not see any gold flaking/peeling off when I was doing it.


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## banjags (Jul 7, 2008)

flankdrive04 said:


> If the tracks are indeed Gold Plated, then how much damage are you doing by scraping of the solder mask? Is there a chemical that removes solder mask quickly and easily??
> 
> Cheers!



A strong mix of sodium hydroxide will remove some types of solder mask. It will not remove all of them. Otherwise you would need solder mask remover from a electronics shop... It may not be worth the cost given the small amount of gold plating under the solder mask.


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## Anonymous (Jul 11, 2008)

You can also use Electrolysis to remove the copper. Using your gold as your Cathode and a copper plate as your anode , within 40 minutes the Electric current will rip out all the copper additives.

I like to use a old 486 laptop power supply for doing this, using only about 40 watts of current.

make sure you throw an electrolyte into your water like baking soda.

This will save you mixing harsh chemcials for something as simple as copper extraction.

you can also use this process to remove nickel, iron, and silver.

nice part is to do this you only need two scraps of wire, two gator clips, your two metals (Metal to be cleaned) and attracting plate. Copper for copper, steel for silver, Nickle for Iron, and copper for copper. Nickle for nickle, (Can use Stainless Steel) will strip both nickle and iron.

NIce part is this is safe enough to do right on your kitchen table.


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## goldmelts (Aug 25, 2008)

Lazersteve,

Looking a the picture I have attached, I noticed the top PCB. The gold seems to be plated on a silvery metal. I understand the AP process works with copper. Do you know if it will work with this silver metal?

Would it be better to process separetly from the other memory/card fingers?

thanks.

Goldmelts.


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## lazersteve (Aug 25, 2008)

The silvery color is likely nickel, or tin/lead alloy solder.

The top PCB doesn't look to have gold plated traces under the solder mask.

Steve


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## goldmelts (Aug 26, 2008)

Hi lazersteve,

Thats right, the top one doesn't have gold tracks. I was wondering about the tin/nickel/zinc. Would it be ok to process these fingers with the copper only fingers.

I would think it might introduce too much other (tin/nickel/zinc) metal when processing the copper plated fingers.

Do you think I am being too picky? I was going to separate them up, and process the copper only fingers first in AP, then the tin/nickel/zinc ones after. I'm assuming this will lead to less contaminants/ better purity.

Whay are others opinions?

thank you,

goldmelts


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## lazersteve (Aug 26, 2008)

I wouldn't bother processing the silvery ones at all. Just toss the silvery boards in with the other low grade left overs to be sold by the pound later.

Steve


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## goldmelts (Aug 26, 2008)

Hi all,

I must be confusing everyone.

The pictures at the start of the post, are the boards minus the gold plated fingers. The question I was asking lasersteve was about the fingers not he boards?

Does that make sense?

So basically, should I process the fingers removed from boards that have tin/zinc together with the fingers that only have gold plated on copper?

hope i'm not confusing everyone?


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## lazersteve (Aug 27, 2008)

The fingers can all be processed together.

Steve


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## goldmelts (Aug 28, 2008)

cool, thanks for your help.

goldmelts


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## n3vrs0br (Nov 18, 2008)

Dichloromethane.

After chasing this issue across the internet, I found that this seems to be the answer.
It is used by electronics techs to remove solder mask.

http://www.jtbaker.com/msds/englishhtml/M4420.htm

_inaccurate information removed. _ NOT to be made at home.

here's the wiki: http://en.wikipedia.org/wiki/Dichloromethane

mike


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## Lou (Nov 18, 2008)

Well it's not expensive, nor is it unstable, but it is likely beyond most people to make at home.


I know I mentioned on this board that DCM can be used. It was probably when I first came here.


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## lazersteve (Nov 18, 2008)

The real problem with using strippers and solvents for removing the solder mask is the added expense, waste stream, and labor.

By requiring yet another chemical and process the possibility of any kind of profit from the boards is reduced considerably, assuming they were not acquired for free. 

The mask will come off with sodium hydroxide solution also, which can be purchase over the counter from just about any hardware store as a non-acid drain cleaner. Again this just adds more expense. 

I save all my board remains to sell at a per pound rate in bulk.

The only exception to this are the ones with all gold plated on all the traces, including the traces under the solder mask.

Steve


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## Lou (Nov 18, 2008)

The nice thing about DCM over lye is that it isn't nearly as hazardous. The chief worry with it is its narcotic effects from working with it in an enclosed space, as it is fairly volatile (boils at around 40 C/100F). 

It can be had for about 8 bucks a gallon from any good solvent distributor. It's also easy to purify--simple redistillation will give suitable quality.


Bottom line is that I still wouldn't bother.


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## n3vrs0br (Dec 4, 2008)

Thanks Lou! I stand corrected, and I found the post from early last year where it's referenced. The best price I could find was from Alfa-Aesar for $26/L, ACS, 99.5+%, stab. with amylene.

Also, would DCM react badly to being distilled through a copper condenser coil? 

Mike


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## Lou (Dec 4, 2008)

Well, you are paying for ACS quality, which means that it must pass all sorts of analyses and be purified by a professional synthetic chemist to strict standards. You pay for those 3 letters!

Technical grade DCM can be had from many companies that specialize in paint strippers; if they have ethyl acetate and acetone, they will have DCM, usually at a couple bucks per liter. 


As for distilling it through copper, you would probably be fine so long as it is DCM not chloroform or carbon tetrachloride because at higher temperatures, they may in fact react with the copper at their higher b.p. and your distillate might be colored.


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## n3vrs0br (Dec 4, 2008)

Lou said:


> As for distilling it through copper, you would probably be fine so long as it is DCM not chloroform or carbon tetrachloride because at higher temperatures, they may in fact react with the copper at their higher b.p. and your distillate might be colored.



I'd run the coil in an ice bath, same for the reciever. I'm just trying to decide between DCM or lye. At my level, I'm thinking lye for now, since I already have all the saftey gear for it. But, DCM being as re-useable as it seems to be, I'd prefer it. I assume refrigeration would be the proper storage method for idle DCM? I doubt I'll be working with CHCl3 or CCl4.

mike


Best pick-up line?
"Excuse me, ma'am, does this smell like chloroform?"


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## carasoph (Jan 29, 2009)

Hiya all,

After having the same issues with numerous cards, I've done some experiments with the ratios of water+Sodium Hyroxide and I the best results came from this one...

4 Galons of Tap water, warmed to around 122F.
Add 1Lb of Sodium Hydroxide and stir to dissolve...
NOW - here is the tricky part - the water are already WARM...so be EXTRA careful here - the almost reach the boil point in a matter of SECONDS!!!!!!! be sure you wear FULL protection gear (gloves, long sleeves and goggles).
As soon as the SH dissolve - toss the cards inside for 6-12 hours, depending on the ammount.
Rinse with water to clean - it usually needs nothing more the just the water to remove the mask off...

Hope this helps...


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## SilverFox (Jan 29, 2009)

After looking at this... It almost seams safer to eat crushed glass.



> Hazards Identification
> 
> Emergency Overview
> --------------------------
> ...


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## rainmaker (Mar 8, 2009)

I have several questions on the use of Sodium Hydroxide to remove soldier mask. 

How do you dispose of it? 

Does it need to be neutralized?

How do you know when it becomes ineffective/and or needs to be renewed/replaced?

I have used it in the crockpot and after several batches of boards it is now a clear brown with a layer of sludge/mask pieces.

Rainmaker


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## goldsilverpro (Mar 8, 2009)

If you were to hammermill the boards to about 1/2", you may be able to leach with something that would dissolve both the copper and the gold - HCl/bleach? - HCl/strong H2O2? The hammermill would really gnarl the pieces and expose a lot of copper edges to the acid. It may take awhile for the acid to get underneath the mask. You could speed it up by pouring the acid out and back, every so often, by applying some heat, or by attaching a hopper vibrator to the bucket - or, all 3. I have tried the vibrator for another application and it worked great. Wood shredder/chipper?

Of course, you could dip the boards in liquid nitrogen, right before you hammermill them. You might end up with gold plated copper, solder, and resin/glass powder. Maybe you could pan off (or, blow off) the powder.

Just thinking out loud.


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