Gold on sound cards? Gold VS. Copper

[Golddigger Greg]

I also ran into the same issues. There was a very little amount of gold that was stripped along with the solder mask on a couple of boards. Removing the card from the stripping solution as soon as possible and using an old toothbrush to scrub the remaining mask off worked for me. Like Marcel said, the plating was very thin and dissolved in A/P. In the future I'd just cut the fingers off and toss the board in to the PCI box to ship.

 

[AndyWilliams]

I also ran into the same issues. There was a very little amount of gold that was stripped along with the solder mask on a couple of boards. Removing the card from the stripping solution as soon as possible and using an old toothbrush to scrub the remaining mask off worked for me. Like Marcel said, the plating was very thin and dissolved in A/P. In the future I'd just cut the fingers off and toss the board in to the PCI box to ship.

GG,

Why would the plating dissolve in A/P? Doesn't that work like Nitric?

 

[Geo]

it depends on how much oxidizer is in the copper chloride solution. copper chloride will not dissolve gold. if you are processing items with thin plating over a copper underlay, do not use fresh hcl and peroxide. use copper chloride from a previous batch and it doesnt matter how finely divided the gold plate comes off, it will not dissolve.

 

[g_axelsson]

I've also seen that the gold surface could turn almost white if it sits in the lye too long. I suspect that it is tin that is dissolved in some places and cemented out on other tracks that have contact with another base metals. The card I saw it most clearly on was an old HP (Hewlett Packard) computer card, one of the fingers turned all white while the one beside it were golden and not affected at all.

If it looks like the gold flash is dissolving it is probably because it is so thin and breaks down into dust that is hard to see. It is also very light so it stays suspended in the liquid a lot longer and is easier to pour out with the AP at the end.
If you want to know how massive the gold on the tracks is, just put a drop of nitric on an exposed surface and watch what you get after the copper is dissolved. Then decide if it's enough value to mess with.

/Göran

 

[Golddigger Greg]

I misspoke. It didn't dissolve, it was as Goran described; finely divided and settled as a near-black powder in the bottom of my leach bucket.
I was so sure that gold had been stripped along with the mask that I saved the solids from the lye bath, incinerated them, rinsed, and placed them in a test tube with fresh HCl.

 

[butcher]

From the looks of that test tube, it appears some gold did dissolve into solution, and is being reduced by tin.

 

[Golddigger Greg]

Yep, I thought it looked pretty neat with the stratified layers like that! 8)

 

[g_axelsson]

If you find gold in the lye bath it is probably from gold freed by dissolving solder. Any solder on gold dissolves the gold when it is melted. I guess that it could form a colored solution as the gold should be very fine particles when the tin is removed.

You should have found your gold flash suspended in the AC solution.
Do you still have it? Pour it into a glass jar, let it settle and look thru the bottom for any fine golden dust.

/Göran

 

[Golddigger Greg]

I do still have it, and will get around to it eventually. Just too many irons in the fire to worry about the little bit in the test tube for right now.