How much gold do you think?

[Brad13133]

Front and back picture of the foil peeled off the circuit board.

 

[Golddigger76]

When the foils peal off like this they are plated pretty thick with gold.
It's not going to be as much gold as you would think, there's still a layer of copper and possibly nickel under the gold but definitely more than mosr modern electronics .
What did this board come out of ?

 

[Brad13133]

When the foils peal off like this they are plated pretty thick with gold.
It's not going to be as much gold as you would think, there's still a layer of copper and possibly nickel under the gold but definitely more than mosr modern electronics .
What did this board come out of ?

Came out of an A/C power source. The brand/company/manufacturers name of of “California instruments” and it was “A/C power source model 3001TCA” made between like 1985-1995 about if I had to take a wild guess. It’s some very complex equipment, but it’s outdated, and was not worth trying to resale as it wasn’t operable anymore, and dealing with freight shipping etc. so I scrapped it.

 

[Alondro]

I've had a few pieces like this that had VERY thick gold foil, so thick my usual HCl-bleach method couldn't dissolve it, even after several rounds in which all the other typical thin foils dissolved swiftly.

 

[macfixer01]

Front and back picture of the foil peeled off the circuit board.

The fact that the gold didn’t flake off as fine dust tells you that it’s not ENIG. It doesn’t really tell you exactly how thick it is though? You’ll get a better idea once you start processing and see how intact the foils stay. That’s a point I’ve made before about the nice looking HP boards with all gold plated traces. You can have two that look identical otherwise, but one will be ENIG and the other has decent plating. Until you either process them or try peeling a piece of trace off each, you don’t know.

 

[BShan]

The fact that the gold didn’t flake off as fine dust tells you that it’s not ENIG.

.....

Until you either process them or try peeling a piece of trace off each, you don’t know.

If I understand correctly, are you saying that ENIG often will flake off of the copper trace when peeling, so peeling a sample trace is a decent way to help identify ENIG? I've heard of the eraser trick but could never get it to work.

 

[Yggdrasil]

.....


If I understand correctly, are you saying that ENIG often will flake off of the copper trace when peeling, so peeling a sample trace is a decent way to help identify ENIG? I've heard of the eraser trick but could never get it to work.

ENIG will even crumble to powders if you dissolve the substrate with acids.

 

[macfixer01]

.....


If I understand correctly, are you saying that ENIG often will flake off of the copper trace when peeling, so peeling a sample trace is a decent way to help identify ENIG? I've heard of the eraser trick but could never get it to work.

Yes, or also as Yggdrasil indicated. After dissolving the copper away, better gold plating will stay in foil form but ENIG will turn into powder.

 

[BShan]

Yep, that's the test I use currently, I was just looking for a "lazier" way. I do all desoldering or otherwise messy teardowns and wetwork outside, including sample tests, but have a workroom in which I do my sorting and physical depopulating which may be less risky, so I was hoping to find a method that was more physical like peeling or abrading.

I reckon there's a bit of wisdom I can pick up here: when the acid test is about as definitive as it gets, I shouldn't go looking for other, less certain methods.

Thanks y'all!