Estimating gold content of "probe pins"

Remember Gold ounces are bigger than iron and nickle ounces.

Paul

Unless the pins date from the days of $100/oz gold (early 1970s), I'd be surprised if it was more than 1/10 to 1/20 of that (maybe 10 cents worth each). They've gotten very adept at using selective plating etc. to reduce the amount of gold in connectors and pins.

Check current prices for "pogo pins". For example, these are very high quality US-made pins:

0.70 each in only 500 quantity, so there's probably only 5-10 cents gold in them at most.

Best regards, Spehro Pefhany

Good point, I forgot all about it.

i

If you post your question here:

you will probobly get the most accurate answer on how much gold you realy have.

Best Regards Tom.

Why isn't the denser metal ingot -smaller- than the others?

Way back in the late "60's I was involved with cleaning the gold plated contacts on the circuit boards of a couple of RCA 110A computers. The contacts were first sllver plated and then gold plated over the silver. The gold plating was so thin that the silver migrated thru the gold and tarnished. I do not remember how thick the gold plating was, but it was considerably less than 50 microinches. This was on pretty expensive computers. So your assumption that the gold plating in 50 microinches, may not be valid.

Second you assume that the pins have the same thickness on the inside and outside. That may be correct, But it is very difficult to plate the inside of a hole. So that assumption may also not be valid.

But I would think that you have established the maximum amount of gold that might be on the pins.

Dan

"Ignoramus21620" wrote in message news:T8SdnQQvBok4a4PMnZ2dnUVZ snipped-for-privacy@giganews.com...

I suspect the plating thickness may be less than half that. The Everett-Charles Industries web site doesn't give Pogo Pin plating thickness, but 50uInch is an extreme, not an average. I don't remember specifying over 15 for card edge connectors, or 5 otherwise. jsw

The last I saw was in Microns.

At this point I am not sure what auction it is from, but I was digging through my "get to one day pile" and accidentally found a couple of lbs of gold plated industrial probe pins:

I decided to estimate gold content.

I looked up online and found that the best gold plating is 50 microinches. So, I assumed that thickness, as these are very expensive industrial pins.

50 microinches is appx. 0.001 millimeter.

I further assumed that the pins are 0.1mm thick wall (they are hollow tubes inside, they are spring loaded).

So, on a 0.01mm material, there is two layers (inner and outer) of

0.001mm gold plating.

That is 0.002mm, or 2% by volume.

Since gold is 3x heavier than other metals commonly used for those pins, like iron and nickel, then the gold content is 6% by weight.

For 2 lbs of pins, they could contain 1.92 oz of gold.

Am I way off here?

i

The expense of industrial parts more often relates to precision. Gold plating is seldom an ideal process, since points, edges, tend to get thicker plating, and hollows get less, reducing the precision of parts. Gold plating will be put on according to engineering needs, and thicker is normally needed only when resistance to wear, or corrosion, is needed. I doubt either is the case here. I'd assume here it would be like the gold plated connectors on circuit boards, there to prevent minor corrosion/oxidation, and to enhance the electrical conductivity. This normally doesn't need thick plating, but exact thicknesses is something I cannot guess at.

.01 mm is really really thin wall material. I'd bet your tubes are at least slightly thicker, since they need to resist mechanical deformation. Remember that these, for electrical conductivity, are likely to be non-ferrous metal, so not as strong as some things might be. But again, I'm guessing. Also, I seriously doubt that there is any gold on the interior of the tube. Getting it there would pretty much require either a process other than electroplating, or would need plating to be done before the stock was made into tube. Unlikely. Getting gold to plate evenly into the interior of simple depressions is alreay hard. Getting to the interior of something deep, like tube, pretty much requires an anode in the plating process to be inside the tube. Unlikely. And most likely, not needed. So assume plating only on exterior surfaces where you can see it..

I would expect either a copper or copper/nickel alloy...

Could, of course, is an open term. Likely? I doubt it. Compare this to gold plated costume jewelry. For several pounds of typical scrap electroplated costume jewelry, one might expect refining returns on the order of a gram or two per pound. But again, it varies widely.

May I suggest that you post this question a well, to the "Orchid" mail list forum hosted on

That web site, set up as a service to jewelry makers and metal arts workers, is one of the busiest discussion forums on the subject on the net, and the mail list, by far the largest such forum, far busier than this newsgroup ever was, even when it was active, which it now is not. The Orchid list (which is not about flowers. It's about jewelry related topics. It's named "Orchid" because it's owner is in Bangkok, where there are Orchid flowers everywhere...) currently has something like 12 thousand active subscribers. Post your question to that list, perhaps asking for off list direct replies so you can find them without needing to read the list, and you are guaranteed to have reached a fair number of professionals in precisely the fields you need to reach for your answers, ie refiners and scrap metal dealers who've dealt with various forms of industrial gold plated scrap metal before.

cheers

Peter Rowe moderator (still, though not every day anymore since now there's seldom any activity) rec.crafts.jewelry newsgroup

I just did a couple of things. One is that I ripped one pin up, and found out that that particular one was gold plated inside. (this actually makes perfect sense, considering that they are spring loaded and the inside has to make contact with the pin). Another is that the wall thickness was close to my guess, 0.11-0.12mm.

i

Is there some way to measure it?

i

You could look up fire assay and aqua regia. Google results aren't loading very well for me tonight, a common problem with graphics-heavy pages on dialup.

I spent half a day today reading about this stuff.

i

Do you have a tool maker's microscope or video measuring microscope? If so, embed the pin in a block of acrylic resin, epoxy, or solder. Then machine the block at a known, very shallow angle so that you cut across the surface of the pin at that same known, shallow angle. Polish the surface with fine sandpaper ending at least with something like 1 micron grit used for fiber optics. If you do not have that, buff with a felt wheel but the results will be less accurate. Measure the horizontal width of the exposed gold layer on the surface, and multiply by the sine of the cut angle to get the gold layer thickness.

PCB QA guys use desktop beta backscatter instruments. Quite fast to get a measurement if you had access to one.

Best regards, Spehro Pefhany

We learned metallographic sample preparation in college.

IIRC the polishing medium was rouge on felt. The grinding machine turntable rotated fairly slowly, like a record player. The arm dribbles water onto the felt to flush away the grit.

After polishing we etched the sample in acid to improve the contrast. The samples disks were about the size of a stack of 5 quarters, large enough to handle and rotate while polishing. Acrylic casting resin worked well though it took a while to harden enough to withstand polishing. Black Bakelite also worked well, and hardened fast enough to polish during the same class hour. There was some advantage to using a clear material so we could see the sample while sanding into it, but not enough to rule out epoxy if that's all you have. jsw

I tried to reply last night, it didn't show. Please pardon duplicate, if that happens.

I think your estimate is quite high on gold content, you'd be lucky to recover more than a gram.

I did gold recovery on quite a big pile of old gold-bearing electronic scrap, and so far have got almost one ounce of medium purity gold. That was from a number of pounds of card edge fingers and pins.

You ought to see if you can sell these as is, for use by small companies or hobby-level shops that need to make test fixtures. I use some of them in my shop for testing production boards. They sell new for over $1 each.

Look at gold-plated connector pins, obviously they are not selling these below cost. Most of these pins sell for a couple cents each, including all the other manufacturing steps.

Jon

I think your estimate may be high. You might be able to get a much better return by selling these on eBay as spring-loaded probe pins, give the dimensions, spring travel, type of tip, etc. These things cost several $ each new, and some small businesses might have use for them for in-house test fixtures. I use a number here in a test fixture for my boards.

Jon