Full Gold tracks?

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goldmelts

goldmelts

Well-known member
Joined
Jun 15, 2008
Messages
76
Location
Astralasia
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.
 

Attachments

  • goldcard.jpg
    goldcard.jpg
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Before you jump for joy, peel one of the traces and drop it in a small mix of AP (10 mL 2:parts 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
 
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!
 
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.
 
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!
Click to expand...

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.
 
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.
 
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.
 
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
 
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
 
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
 
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? :D
 
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.
 
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
 
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.
 
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
 
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.
 
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.
Click to expand...

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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