# Question about waveguides and some silver plated stuff



## darshevo (Nov 3, 2010)

I have spent the last few weeks processing a bunch of pieces I got from the county auction that came out of the old radio system. I picked up (possibly incorrectly) from another forum topic that some wave guides are gold plated on the inside. I was hoping someone would recognize these and be able to say yes / no. The appear to be plated, but they are made of yellow brass and we're up until very recently in a sealed unit. Therefore I could just be looking at some nice clean untarnished yellow brass.

Also, rather than start another thread for these guys figured I would bunch them all together. I have quite a few of each piece. Tarnish and application has me 95% sure these are silver plated. My main question is are they worth attempting to do anything with, or something to toss in a box against a future big spike in silver prices? 

The last one I am wondering about is the small unit pictured with the screw. I believe its a transistor? The base has is gold plated. I have a small collection of boards with quite a few of these on them. Same question for them, are they worth the time of removal, or should I just toss them into the board bin as is?

As always, thanks for taking the time to look

-Lance


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## FrugalEE (Nov 3, 2010)

Nice haul. I recently sold brass at $1.80 a pound. That is definitely a Motorola transistor. It appears to have some kind of special house number as opposed to a standard number like 2N3866. I'm a bit rusty on reading date codes, but it looks like it was made in 1991. I looked in my Motorola handbooks, but failed to find any data on plating thickness. The gold plating is strictly for solderability or looks so it's apt to be pretty thin. In some applications the case (collector) might be soldered or clamped to a heat sink. Try GSPs eraser test for thickness, make a judgement on thickness and multiple by area to get an estimate of the gold. I have a lot of old RF stuff so please post your results if you strip a bunch of these.

Waveguides are above the frequency range of RF I worked with so I can't comment there, but silver would normally give the lowest loss. The basic tube could even be iron or another poor conductor if the inside was plated with copper or silver.

I'm quite interested in stripping silver from copper or brass, but from what I've been able to glean from the board I don't think there is a very easy or economical way to recover the silver. I'm going to be very slow to give up on that.


FrugalEE


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## Oz (Nov 4, 2010)

darshevo said:


> Also, rather than start another thread for these guys figured I would bunch them all together. I have quite a few of each piece. Tarnish and application has me 95% sure these are silver plated. My main question is are they worth attempting to do anything with, or something to toss in a box against a future big spike in silver prices?
> 
> -Lance



I have little clue as to your potential silver yield (it may be uneconomical to recover at $50 silver) but have you looked at silver prices lately? If this is a ho hum increase we are seeing in your opinion, I would hate to see what you call a spike.


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## butcher (Nov 4, 2010)

For information only:
this sounds so dangerous I hesitated to post it.
From sources I have read, I never tried this.
Was used by metal platers to remove silver from plated objects.
Silver plate stripped from flatware
One part conc. HNO3, and six parts conc. H2SO4, used in hot water bath or sand bath 160 degrees, will work slower at lower temp.
Some sources say 10% HNO3 and 90% H2SO4, the plated object is the anode, you do not want water in solution (but when all water is gone it will start fuming SO2 gas (so maybe some water to keep so2 from escaping),(Caution do not add water to concentrated sulfuric acid) if much water in solution it will start attacking base metals (copper, brass), so only enough water to keep SO2 in solution, lead or stainless as cathode,
Dilution of solution (acid added to water)when done and adding NaCl, or HCl should precipitate silver as AgCl, which will need converted to elemental metal before melting.

Note of CAUTION this hot concentrated acid would be very nasty and Very dangerous, very dangerous burns, not something to be messing with in the back yard,

I do not recommend this for anyone to try. That little bit of silver would not be worth the risk.
--------------------

cannot say this process is economical:
Here is a safer process I use, all my solutions here are used solutions, except for small additions of new chemicals, and it helps me reuse some of my used solutions, the silver produced from this still has some copper after melting but is mostly silver, and I will reprocess it for higher grade silver, can also use for in quartering gold later.

I have been using a safer (than the one mentioned above the platers used) cell to remove the silver (and copper, brass) as a fluffy powder,
The cell use’s very dilute H2SO4 and water, or used copper sulfate solutions, as the electrolyte, the fluffy copper powder from cell is rinsed, then I use (used acid peroxide saved from other processes), first the brown used acid peroxide solution is heated in coffee pot (not too high as I do not want to burn powder to bottom) this heating changes my copper/silver powder from the cell, to copper I chloride and silver chloride both white powder, this powder is moved to a canning jar, I use a small funnel, and a plastic tool that has a screen in bottom, some type of plastic screen (I do not know what kind but it has held up very well to my acidic solution’s), this filters out any bigger pieces of copper and gives me a chance to bust up any clumps of silver chloride, classifying the powder for further treatment, now this copper I Chloride and silver chloride, solution is dark brown decanted, and repeated , I add more used acid peroxide this time the light green solution with oxidizer left in solution, some additions of HCl and peroxide as needed, ( if solution goes brown still much copper I chloride to get out , this repeated, until as much copper I chloride (white powder), as I can dissolve from the silver chloride (white powder), this is done until hot HCl no longer picks up copper I chloride powders, and mostly silver chloride powder remains, this is then converted to elemental metal and dried, heated and incinerated, before melting, there is some copper in my melted bars but these can be reprocessed to get that out later, this uses up some of my old acid solutions (although even after this process I still reuse the solutions left from this one)and gives me some impure silver from plated objects I have collected, there are some details about this that is hard to explain, but if you understand the acid peroxide process then you can figure them out. Silver plate seems like a lot of trouble for the silver, (nitric cost too much and too much copper in plated material) I cannot tell you that it would be worth all the trouble I go through to get this silver. but I do get some impure silver.


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## darshevo (Nov 4, 2010)

FrugalEE said:


> That is definitely a Motorola transistor. It appears to have some kind of special house number as opposed to a standard number like 2N3866. I'm a bit rusty on reading date codes, but it looks like it was made in 1991.



You are probably just about right on with the date code, most all of the stuff I have pulled out of these machines has varied from 85 to 93 or so

Oz: I know that silver is on a tear right now, that's why they didn't go right across the grinder to determine base metal and strait into that bin already (I did that with several hundred lbs of connectors last year and am now regretting it some) 

Butcher: I tend not to be too adventurous. I haven't messed with any acid yet, for me the bulk of the fun is tearing the stuff apart (see how long that lasts the first time I have a button). Plus, as long as prices hold/raise I am not in a huge hurry to process anything. For now I am getting the required reading together (Hoke, GSPs book, Steves DVD's, and TONS of the posts from this site) I appreciate the methods, this thread will be going into my book marks for sure. 

-Lance


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## nickvc (Nov 5, 2010)

darshevo said:


> FrugalEE said:
> 
> 
> > That is definitely a Motorola transistor. It appears to have some kind of special house number as opposed to a standard number like 2N3866. I'm a bit rusty on reading date codes, but it looks like it was made in 1991.
> ...


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## FrugalEE (Nov 5, 2010)

http://www.goldbulletin.org/assets/file/goldbulletin/downloads/Asher_1_13.pdf

That URL will take you to a paper where the author discusses plating of transistor headers. He states that they used to be plated with 3 microns on small transistors such as TO-18. Your transistor is more like a TO-5 and much larger, but I expect in the old days before gold got pricey they got about the same treatment. The reason for the gold is primarily the mounting of the chip on the inside and I guess the bottom generally got plated also because it cost too much to mask it off. The author then states that many are now finding ways to get by with only 0.25 microns and some are even selectivly brush plating that in the area where the chip goes.

You should remove the cap of a transistor and look inside and find many have the bottom gold. Also there is gold on the bottom of the chip but its not very significant and hard to get to.

Let's assume we have a transitor similar to yours (TO-5) and that it is plated with the full 3 microns. I used the drawing for a Motorola 2N3866 to get dimensions and averaged between the min and max.

The area (ignoring the glass seals) is 62.9 mm. (I also ignored the vertical dimension and the leads.)

The volume is .1887 cubic mm or divide that by 1000 to get cubic cm
Gold weighs 19.32 grams per cubic cm
There are 30.103 grams in a troy ounce
weight of the gold on that surface is 0.00365 grms
at $1300 per ounce of gold that is worth $.152

I think if you can find enough of the older transistors and find a good way to remove the top cap it would be worthwhile as a hobby to deplate these in a cell such as Steve demonstrates. I need to do much further investigation. There are large power transistors that are gold plated.

It's been about 10 years since I retired as an electronic engineer and I'm a bit rusty, but I did remember that transistors are covered in Mil-S-19500/ with a slash sheet for each type. I looked up the sheet for 2N3866 (/386 I think it was) and found that it said nothing about gold plating except that the leads be solderable per _____. It did state that the bottom of the chip was to be gold based with a thickness of 6500 Angstroms +/- 1,950 Angstroms. This was on a die only .016 X .020 and it takes 10,000 Angstroms to make a micrometer. Mil specs are primarily interested in standardizing performance, testing, and especially reliability. They generally don't tell you in detail how to build something.

I looked through a collection of old transistors 2N3866 I had and found that some brands are gold on bottom and some brands are not and also some Motorolas were with gold and some without. I also did a bit of erasing and it held up well, but most of my stuff is pretty old.

Date Codes: I remember now that codes are usually 4 numbers with the first two being the year and the next two the week in the year thus 8852 would be one made the last week of 1988. 

I appoligize if most of this has already been covered on the forum.

FrugalEE


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## darshevo (Nov 6, 2010)

Excellent info Frugal. I went ahead and tore into one with a pair of wire cutters and it is indeed plated inside as well. Did the eraser test and it seems to hold up well, although I am curious about the base metal. I gouged it pretty good getting it apart and it appears to be brass, in which case I could be misleading myself with the eraser as it would be polishing the brass as the gold came off giving it the appearance of a consistent plating. 

-Lance


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## goldsilverpro (Nov 6, 2010)

Arthur Kierski got $142/pound in gold from TO5s in this thread, with a much lower spot price (around $950/oz) at that time. Most of the older TO5s were made of magnetic Kovar. In the 60s-early 80s, you used to see these on almost every board. The smaller ones, TO18s, were also common and they ran higher/pound because they weighed less. We used to get drums of both varieties, loose, as rejects from manufacturers.

http://www.goldrefiningforum.com/phpBB3/viewtopic.php?f=34&t=5535&p=47508&hilit=to5+arthur#p47508

The best TO5s I have seen were painted black. You could scratch off the paint and see gold on the entire piece. I would guess they were made in the late 50s-60s.


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## Anonymous (Nov 6, 2010)

GSP,I cannot access the pic in that link.Please advise if these are the same or similar.Thank you.
Images deleted


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## FrugalEE (Nov 6, 2010)

GSP,

Thanks for that reference. It's mind boggling to hear you've refined "tons" of TO-5 and TO-18 transistors. So the solder inside is a big factor. I had not yet picked up on that.

I've known that the can was magnetic, but not that it was full of Nickel and Cobalt. With nickel now running over $10 a pound it seems that at least on a large scale one should be electro recovering the nickel and cobalt. There are also nichrome heating elements as a good source of nickel.

I'm going to have to look and see if I have any of those black painted gold transistors. I'll bet I have a few to play with. What I do recall though is that some of the early germanium transistors, especially RF types from Philco and Sprague were all gold plated. 

The paper I referenced earlier was on an experiment to find out if electroless plating of headers would work as electroplating was concentrating the gold in the high spots like at the ends of the leads. I suppose the bonding wires inside also had gold content.

FrugalEE


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## FrugalEE (Nov 6, 2010)

Mic,

I too am very curious about old power devices like you have shown. I think GSP was refering to much smaller signal types that look like top hats.

What many of us need is a good way to estimate the plating thickness, sort of a touch stone kit kind of thing. GSP's eraser method comes pretty close, but I'm afraid the abrasiveness of the erasers vary quite a bit with their age and type and even the hardness of the gold plating probably varies somewhat. One thing that would be useful is to have calibration standards. A plater could supply samples of standard plating thickness or readily available plated objects could be used once someone with the right equipment or techniques determined their thickness. 

Love this forum,

FrugalEE


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## goldsilverpro (Nov 6, 2010)

Here's a typical TO5. I would guess they are about 1/4"-5/16" in dia. Many have longer gold plated leads than this.

I know that the volumes I speak of sometimes sound exaggerated. Please remember that most of the refiners I was associated with dealt mainly with reject scrap from electronic manufacturers. At that time, it was said that 40% of all the gold purchased by these manufacturers ended up as scrap, in one form or another - this figure may, or may not, have improved since then. For example, with TO5s, we might possibly receive scrap in the following configurations: (1) just the gold plated headers (and leads, of course), with no lid or chip, (2) gold plated headers with chip and bonding wires - no lid, (3) fully assembled with chip and lid. Usually, these came in separate drums and were not mixed. Also, it was not unusual to receive a lot of 10 drums of loose reject gold plated pins or 5 drums of reject gold backed silicon wafers. Most of this stuff was stripped in cyanide. Some material, like the fully-assembled TO5s, was digested in acids, in order to get the gold under the chips.

We also did populated boards. However, we just incinerated these and shipped the bars and pulps to a smelter. With few exceptions, I can't remember anyone sitting there cutting off fingers or pulling parts off the boards. This was usually not cost-effective.

mic,

Those on the left of your photo are TO3s and, even the best of these are worth far less/pound than the TO5s and TO18s that have gold plated headers. The main reason is that the TO3s are very heavy in base metals. Some of the TO3s have a large, thick, heavy chunk of copper on the inside, for example. Most TO3s package diodes.

All of these, the TO5s, TO18s, and TO3s, come in many, many, many varieties. This can range from all gold plated, including the lids, and a gold soldered chip, to no gold plating and an epoxied chip - with many different configurations in-between. Also, some have long legs and some have short legs. Each deal is different and it's difficult to predict the values. In general, the older, the better.


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## Anonymous (Nov 6, 2010)

Thank you.Near where I live,there is an electronics supply warehouse,with every kind of component imaginable,which is where I purchased the T03's.They also sell countless amounts of pins,transistors,IC's..etc sometimes for pennies apiece.They have literally hundreds of pounds of these components.They have a scale that can cross "per piece" price,with "per pound"price and one particular pound of pins that I brought for them to check came out to be $28 for one pound.I will be heading back over there after I finish getting this next load from the military.


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## FrugalEE (Nov 6, 2010)

GSP,

As far as you know is the plating on those old power transistors just as thick as on the older TO-5s and TO-18s? Do you expect something in the order of 3 microns like that Motorola paper I referenced earlier?

The large amount of copper suggests to me that stripping rather than digesting needs to be the recovery method.


FrugalEE


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## qst42know (Nov 6, 2010)

> The large amount of copper suggests to me that stripping rather than digesting needs to be the recovery method.



Keep in mind you need a way to get the packages open and that some are thermal grease filled.


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## FrugalEE (Nov 6, 2010)

I've only opened a few power transistors in my life time and some have opened themselves when they shorted out, but none of them had thermal grease in them. I saw that post when I was searching all the transistor hits. I wonder if there is a quick test to see if berillium oxide is the fill used in the grease. I have quite a few RF devices that might have BeO insulation. Also I've used thermal grease off and on through the years and wondered if it had Be in it and was I doing myself harm applying with my finger application. I did a brief check on the hazards and found that it is primarily breathing the dust of Be that causes lung allergy problems in 1 to 15% of the population. Grinding, crushing, etc should be done with great caution if done at all. Breathing metal fumes is the other way one could be poisoned. As long as it stays in grease it seems pretty safe, but it doesn't look like torching grease is a good idea. It may be better to use a solvent.

FrugalEE


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## qst42know (Nov 6, 2010)

Good call on the beryllium oxide in the grease. Something I hadn't considered.

http://en.wikipedia.org/wiki/Beryllium_oxide

This transistor is an RCA. Nothing special except for the grease. I tried to pinch the top off with nippers.

Something else to consider while incinerating with this old stuff, it may have old school cadmium plate.


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## goldsilverpro (Nov 6, 2010)

I haven't heard of any cad plate on electronic components.


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## qst42know (Nov 6, 2010)

Would they reveal it if a plated item was cadmium? It wasn't an issue not to long ago.

It used to be a very common choice, cadmium plate. I can only guess it was a cheap effective easy process. I remember cadmium plated nuts, bolts, and screws back in the seventies.


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## goldsilverpro (Nov 6, 2010)

They're not going to just throw cadmium on something for kicks. They would have to have a technical reason for it. Cadmium was primarily used as a sacrificial coating to prevent steel from rusting, for nuts and bolts, etc. I've never heard of it being plated on electronic components and I would wager that it's never been used, as plating, on electronic components. I do, however, remember that we ran into some old CPU packages that used a Ni/Cd braze to seal bare kovar lids.


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## qst42know (Nov 6, 2010)

goldsilverpro said:


> They're not going to just throw cadmium on something for kicks. They would have to have a technical reason for it. Cadmium was primarily used as a sacrificial coating to prevent steel from rusting, for nuts and bolts, etc. I've never heard of it being plated on electronic components and I would wager that it's never been used, as plating, on electronic components. I do, however, remember that we ran into some old CPU packages that used a Ni/Cd braze to seal bare kovar lids.



Do you know a test for cadmium? 

This transistor may well be a good candidate for corrosion protection, both the lid and legs are magnetic.

I can only point to the modern RoHS standard that specifically restricts the use of lead, mercury, and cadmium. I can't say with certainty where it was applied but it must have been in there somewhere.



> These Regulations implement EU Directive 2002/95 which bans the placing on the EU market of new electrical and electronic equipment containing more than agreed levels of lead, cadmium, mercury, hexavalent chromium, polybrominated biphenyl (PBB) and polybrominated diphenyl ether (PBDE) flame retardants.


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## goldsilverpro (Nov 7, 2010)

Cadmium was never a cheap, common choice. The only reason it is cheap today is because it has fallen out of favor with the environmentalists. It used to be a lot more valuable than it is today - check the price history. Zinc is similar and it has always been the cheaper coating. Cad plated steel has always been of premium quality. Kovar doesn't rust. After all, it contains 46% Ni + Co. If Cd plating was used, documentation would surely exist on it - where is it? Why do you keep showing this meaningless photo of a TO5 that looks like it's been burned? Why are we arguing?


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