# nice old boards



## floppy (May 8, 2011)

These boards are very old and look to have lots of gold. Very excited to process these. I found hundreds of these that look pretty much the same.


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## element47 (May 8, 2011)

Boy, that would seem to be the ideal genre of boards for PC PM extraction: No solder mask and the *entire* trace is gold plated vs just the contact fingers. Very nice!


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## floppy (May 8, 2011)

They do look nice dont they. But they aren't pc cards. They are old telcom cards. I don;t know exactly how old but the one has a repair card attched to it thats dated 1975. So I assume that they're atleast older than that. The traces are very thick. I can actually use a knife to peel the edge of one the fingers up and pull the entire trace off. I'm pretty interested to see what kind of yield these will give. If anyone in here has seen these or processed boards similar I sure would be interested to hear about it.


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## escrap (May 8, 2011)

They are older than that. In the third pick you will see 7026. This means they were made in the 26th week of 1970.


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## floppy (May 8, 2011)

I didnt even notice hose numbers. Funny what you can miss when you're staring at gold. :lol:


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## goldsilverpro (May 8, 2011)

floppy said:


> They do look nice dont they. But they aren't pc cards. They are old telcom cards. I don;t know exactly how old but the one has a repair card attched to it thats dated 1975. So I assume that they're atleast older than that. The traces are very thick. I can actually use a knife to peel the edge of one the fingers up and pull the entire trace off. I'm pretty interested to see what kind of yield these will give. If anyone in here has seen these or processed boards similar I sure would be interested to hear about it.



Don't be fooled by the traces. They are only about 1% gold, or less, by weight, if my math is right. A thin layer of gold over a thicker layer of nickel over a thick foil of copper. And then there's the adhesive.


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## floppy (May 8, 2011)

How did you come up with that number. Do you know those boards or something?


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## goldsilverpro (May 9, 2011)

floppy said:


> How did you come up with that number. Do you know those boards or something?



Keeping it simple, most all boards start with a solid foil of copper (attached to the board material with adhesive) that weighs from 28.4 grams (1 av oz) to 56.8 grams (2 av oz) per square foot. Through a series of masking, etching, and plating steps, the copper is etched away from certain areas, nickel and gold [or any other metal(s) desired, such as tin or Sn/Pb solderplate] are plated on top of the copper, and the desired circuitry is formed. In the case of fingers, the nickel is about .0002" to .0005" thick and the gold about .00003" thick. The gold might be thinner than this but will usually not be thicker. There has probably never been a board made with solid gold traces. It would be extremely wasteful. 

All you need is enough gold to prevent corrosion to the underlying base metals and/or to be thick enough and hard enough to allow multiple insertions without wearing through the gold layer. Also, in some cases, it must be thick enough to act as an etchant mask. For things such as fingers or connector pins, .00003" of gold (about .0095 grams per square inch) is adequate and this thickness has been used at least since I started in this business in 1966. There are thinner or thicker exceptions but the exceptions don't include solid gold fingers or traces.

In re-doing the math, I came up with the gold percentages on finger traces ranging from about 1.5% to 4%, by weight. Sorry about my error. I'm old and it's late.


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## stihl88 (May 9, 2011)

Just be mindful when disposing or inspecting those "Mercury Wetted Contact Relays"

Nice boards BTW,


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## element47 (May 9, 2011)

"PC" can mean "printed circuit" or "personal computer" when referring to boards; or "politically correct" in other contexts.


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## floppy (May 9, 2011)

got ya element. sorry bout the mix up. And thank you for the explaination GSP. I will definitely dispose of the mercury relays stihl. As for the gold content there still has to be more than just processing the finger contacts alone. Especially out of a few hundred or more.


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## Oz (May 10, 2011)

I just have to ask. How will you dispose of the mercury now that you are the owner of it?


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## silversaddle1 (May 10, 2011)

Oz said:


> I just have to ask. How will you dispose of the mercury now that you are the owner of it?



Our local landfill will take mercury switches and so forth, no charge.


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## floppy (May 10, 2011)

I am gonna put them in a bucket for now until I figure out how to properly dispose of them.


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## patnor1011 (May 10, 2011)

He can de-solder them and sell on ebay.


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## stihl88 (May 10, 2011)

I would be reading up on those switches to see if their are any PM's inside, who knows, their could be a nice little chunk of gold inside...
Although the Mercury switches would probably be be a pain to process. 
Could one use heat Distillation to process the switches if there was found to be PM's inside worthy of salvation?


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## maltfoudy (May 10, 2011)

if you take the plastic covers off those relays and turn down the little reeds you will see contact points,i have lots of boards simular to the ones pictured and they have gold color points,very small but they are there.


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## qst42know (May 10, 2011)

patnor1011 said:


> He can de-solder them and sell on ebay.



I am certain there are shipping regulations against that, with stiff penalties if caught.


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## patnor1011 (May 10, 2011)

qst42know said:


> patnor1011 said:
> 
> 
> > He can de-solder them and sell on ebay.
> ...



Probably not. You can buy whole range of electronics or part which contain mercury without any problem. He would not ship mercury by kilos only few relays.


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## floppy (May 10, 2011)

i think I'll probably just find out if there are any pm's inside. I don't really know if there is a law against shipping them and don't wanna find out the hard way.


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## Findm-Keepm (May 13, 2011)

qst42know said:


> patnor1011 said:
> 
> 
> > He can de-solder them and sell on ebay.
> ...



Very true - Mercury can not be mailed. The Universal Postal Union (UPU) specifically prohibits the shipment of mercury through the mail. The US, UK, Eurozone, and 98% of the rest of the world all belong to the UPU, and have to abide by it's regulations.


348.21 Nonmailable Corrosives
Nonmailable corrosives include the following:
a. Batteries (UN2794, UN2795) with liquid electrolyte (such as automobile
lead acid batteries), except for the nonspillable type allowed under
348.22.
b. *Nitric Acid (UN2031, UN2032).*
c. *Fuming and Spent Sulfuric Acids (UN1831, UN1832).*d. Hydrofluoric Acid (UN1790).
e. *Mercury, and items containing mercury, including thermometers*.

In the post-9/11 US, postal inspectors are quite diligent in finding these items. In 2006, I had some reed relays (non-mercury containing) opened for inspection, and a summons issued to meet with the postal inspector at the Federal courthouse. It all came out just fine - I brought along a datasheet, and proved my case once I allowed one to be "opened" by inspectors. Apologies were not necessary, but given by the postal service.

Just some FYI....

Cheers,
Brian


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## element47 (May 13, 2011)

A valuable FYI indeed. You end up with some Feds on your behind as a result of apparently innocent activity and they will make you hate life.


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