Determining Gold plating on Boards

[Anonymous]

I have a few dozen of these boards. I got them from equipment I found in a dumpster. I am trying to figure out what class of gold plating this is. These boards are from tel-com/microwave things. The side that is covered in gold plating was screwed onto a large heat sink (the whole case for this was a heat sink). The board is 7.5in x 4.25in. I have attached pictures of the boards and a spreadsheet with the math that I have done.

Is what I have done so far correct? How can I determine class of plating this is? Are these the only variables I need to take into consideration?
Also wanted to ask if anyone gets newish boards(made within the last 4 years) with Altera or Xilinx BGA chips on them. Or if anyone get DDR memory for server and desktops. I know some people that buy them for a lot more that scrap prices.

I used Silverpro's formula. Thanks Silverpro!
Silverpro's method:

Class 00 20 micro inches
Class 0 30 micro inches
Class 1 50 micro inches
Class 2 100 micro inches
Class 3 200 micro inches
Class 4 300 micro inches
Class 5 500 micro inches
Class 6 1500 micro inches

Daily price of gold times the square inch surface area times the thickness.
Base value figure is 1/1000 Spot price per micro in. X surface area in.
0.655 x (gold price) 40 sq in. x 0.30 (thickness) = $7.86 of gold at today's prices.

 

[goldsilverpro]

Here's the formula.

(spot price/100,000) X (thickness in microinches) X (number of square inches of gold plated area) = $ value

One microinch = .000001" = one millionth of an inch. One micron = 40 microinches = .000040".

The problem is that you have no idea of the gold thickness on this board. For fingers and other parts that have potential wear from multiple insertions, like certain connector pins, you can make an average guess of around 30 microinches. For parts that must be heated in order to attach the chip and lid using gold bearing brazes, like certain CPUs, you can guess 50 microinches. Other than that, ??? The only way you'll really know on anything is to refine it or assay it.

 

[lazersteve]

Those boards look like the ones with barely any thickness to the gold plating. It will nearly wash right off with AP and a toothbrush. It comes off in tiny particles (no foils).

You can rub the gold 'plating' with an eraser and it will vanish in the area you rub.

Steve

 

[Anonymous]

Those boards look like the ones with barely any thickness to the gold plating. It will nearly wash right off with AP and a toothbrush. It comes off in tiny particles (no foils).

You can rub the gold 'plating' with an eraser and it will vanish in the area you rub.

Steve

What class of plating is it if it does rub off with an eraser? And why did you write 'plating' with the quotes? Is this not plating?

 

[samuel-a]

What class of plating is it if it does rub off with an eraser? And why did you write 'plating' with the quotes? Is this not plating?

this is mearly anti-oxidation flashing and not contact point plating.
flash plating = 4-7 µin

 

[goldsilverpro]

Don't dwell on "classes" of plating unless you were there when they spelled it out. It is what it is. To me, as a refiner, "classes" or "mil spec" are totally meaningless terms. Think thin on this particular application, unless you refine it and discover otherwise. I can't think of any technical reason why it would be thick. Can you? If you can't, it's most probably thin. Real thin means 7-10 microinches - about a dime per square inch. It's futile to try and put a lot of this stuff in boxes. It all depends on that particular manufacturer at that particular time for that particular reason. You'll go nuts second guessing. Refine it or assay it and put all this real info in your memory bank.

 

[Anonymous]

Don't dwell on "classes" of plating unless you were there when they spelled it out. It is what it is. To me, as a refiner, "classes" or "mil spec" are totally meaningless terms. Think thin on this particular application, unless you refine it and discover otherwise. I can't think of any technical reason why it would be thick. Can you? If you can't, it's most probably thin. Real thin means 7-10 microinches - about a dime per square inch. It's futile to try and put a lot of this stuff in boxes. It all depends on that particular manufacturer at that particular time for that particular reason. You'll go nuts second guessing. Refine it or assay it and put all this real info in your memory bank.

this is merely anti-oxidation flashing and not contact point plating.
flash plating = 4-7 µin

Now that makes sense. You guys were correct. The plating came off easily


So unless there is a logical reason for using a thicker plating it will not be used. I was hoping that because of the type of equipment this came from and how much it cost originally the manufacturer would just cover it in gold. Thanks for the help.

 

[macfixer01]

Don't dwell on "classes" of plating unless you were there when they spelled it out. It is what it is. To me, as a refiner, "classes" or "mil spec" are totally meaningless terms. Think thin on this particular application, unless you refine it and discover otherwise. I can't think of any technical reason why it would be thick. Can you? If you can't, it's most probably thin. Real thin means 7-10 microinches - about a dime per square inch. It's futile to try and put a lot of this stuff in boxes. It all depends on that particular manufacturer at that particular time for that particular reason. You'll go nuts second guessing. Refine it or assay it and put all this real info in your memory bank.

this is merely anti-oxidation flashing and not contact point plating.
flash plating = 4-7 µin

Now that makes sense. You guys were correct. The plating came off easily


So unless there is a logical reason for using a thicker plating it will not be used. I was hoping that because of the type of equipment this came from and how much it cost originally the manufacturer would just cover it in gold. Thanks for the help.

Well there is the Free aspect, if you could find a cheap enough method to remove the gold. You don't have any cost in them except your time to collect them. You could make some money by selling them to a large recycler. Or you could always put them on Ebay and clear your conscience by noting they're actually low grade scrap. No doubt some would fight over them anyway. Also it appears there are still some gold bearing components such as the T-shaped microwave transistors on the boards which may (possibly) be worth more than the gold flash?

macfixer01