# Gold plated steel ICs and transistors



## Bertho (Oct 14, 2019)

I keep reading the posts and all say "remove iron before proceeding". Unfortunately this scrap is a mixture of gold plated steel IC leads and housings with internal gold wire bonds. I will remove the pins with the nylon. I have had bad experience with nylon before. 
It is a hobby and I am trying to process different types accumulated over decades.
What process steps do you suggest? 
I have build a de-plating cell that I used for regular pins but this is presumably not suitable for it.
I got a fume hood, furnace, and equipment and have previously gone through different regular material and processes. 
I have ball-milled gold ore concentrate that is next on my list to try.
Bertho


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## butcher (Oct 14, 2019)

a search using the phrase 
top hats
https://goldrefiningforum.com/phpBB3/search.php?keywords=top+hats


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## snoman701 (Oct 15, 2019)

Incinerate then digest steel in a mixture of nitric and a little sulfuric acid. Fast reaction likely to boil over and produces a lot of NOx. 

Or, incinerate then just let it sit in hot hcl for a couple days. It helps if you add a bubbler...and it helps immensely to bring it to a light boil on the first day for a bit. 

Depends on how much time you have. 




Sent from my iPhone using Tapatalk


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## Bertho (Oct 15, 2019)

Thank you Butcher and Snoman.
It took a very long time to follow up on Butcher's Top Hat links.


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## butcher (Oct 16, 2019)

Hopefully, in that very long time you have found some answers to a few questions you did not think of asking, and then maybe a few more questions to work with those answers.


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## anachronism (Oct 16, 2019)

butcher said:


> Hopefully, in that very long time you have found some answers to a few questions you did not think of asking, and then maybe a few more questions to work with those answers.



So true. I've lost track of the times I have searched for something in particular only to then spend hours learning other things that have cropped up browsing posts.


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## Bertho (Oct 17, 2019)

butcher wrote: ↑15 Oct 2019, 23:15
Hopefully, in that very long time you have found some answers to a few questions you did not think of asking, and then maybe a few more questions to work with those answers.

Anachronism wrote:
So true. I've lost track of the times I have searched for something in particular only to then spend hours learning other things that have cropped up browsing posts.
---------------------------------------
( I got to figure out how to quote)

Well, after two days on the hotplate @ 80C it is very, very slowly dissolving my tests batch of the 88g test batch.
Then I goofed up: I forgot to replace the watch glass cover and it all dried up. Cooled it off and added 250ml EDIT: HCL, not HNO3 and back on the hotplate. A day later there is still a good amount of undissolved stuff in the beaker.

I got Snoman's advice too late about incinerate which I will do for the next batch.
How much is "a little" sulfuric acid to add to the HCL?
What is chemically happening with the extra sulfuric?
I am off reading again and very likely get sidetracked on other interesting processes. Pyrolysis sounds interesting.


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## butcher (Oct 17, 2019)

Back up a bit and explain better of your plans, and the chosen process.

I may be confused, but it sounds to me from the question you are asking about two different processes.


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## Johnny5 (Oct 17, 2019)

Bertho said:


> ( I got to figure out how to quote)



Click the quotation mark symbol in the upper right hand corner of any post. 
Once you have that persons quote, you can delete parts of the quote, so that only certain parts remain.
If you want to add another persons quote to your post, once you open up a reply window, scroll down until you find the post you want to quote from, and look for the same quotation mark in the upper right hand corner, when you click on it, the quote will be added to your current reply.

You can play around with this, and at anytime you can hit "preview" to see what the reply looks like. Just don't hit the "submit" button on the bottom, until you are satisfied.


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## niks neims (Oct 18, 2019)

Bertho said:


> butcher wrote: ↑15 Oct 2019, 23:15
> Hopefully, in that very long time you have found some answers to a few questions you did not think of asking, and then maybe a few more questions to work with those answers.
> 
> Anachronism wrote:
> ...



I messed up when I first tried to process material like this (mine were USSR transistors), I tried to dissolve them in HNO3, the "hats" were kovar (magnetic) I think, and did not budge, so I decanted copper nitrate and nuked everything with AR, made sure it dissolved everything metallic and cemented the gold out on copper, worked out fine I guess... It was quite a while ago, and while I'm sure that my yield suffered, I remember thinking it was OK...


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## Bertho (Oct 18, 2019)

First, thanks guys for your help. I also now know how to quote



butcher said:


> Back up a bit and explain better of your plans, and the chosen process.
> 
> I may be confused, but it sounds to me from the question you are asking about two different processes.



The goal, of course, is to recover the gold from the plating, wire bonds and gold solder.
I have read several suggestions to use HCl and heat to slowly dissolve the base metals, mostly iron in the transistor leads and the covers and kovar for the transistor/IC bases.
After over 3 days at 80C there is a lot of undissolved parts. I also see gold flakes floating around.
Once there is no more action using HCL I then plan to use AR for the rest.

Later I saw Snoman701 suggestion: "Incinerate then digest steel in a mixture of nitric and a little sulfuric acid. Fast reaction likely to boil over and produces a lot of NOx." My question here is how much is "a little"?

It looks like niks neims ran into a similar problem and switched to straight AR. Actually that is what I ended up doing on my first test batch but on this second batch I tried to carefully follow the suggestions but still no good procedure.
Bertho


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## niks neims (Oct 18, 2019)

Bertho said:


> It looks like niks neims ran into a similar problem and switched to straight AR



It was more of an emotional decision, I felt that those damn kovar top hats are mocking me and my hot nitric, so at that point it was more to show them who's boss  AR made short work of them... he he he

When I will run next (much larger) batch of them (have quite a few stockpiled, but not planning to any time soon) I'will try another route, so I would very much like to see how will you end up dealing with your batch; and please take pictures!

If I were to guess the sulfuric is to help with passivation of iron (steel) in concentrated (68%) nitric (sometimes diluting nitric also helps), it is only a guess though, and maybe it doesn't work on kovar

If i were to run a batch of these now, I'd definitely mechanically remove those hats beforehand with some clippers (pliers?)...


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## butcher (Oct 18, 2019)

Ok, so You were talking about several different processes to remove base metals.

Nitric leach;
Iron will passivate in concentrated nitric acid, diluted it will work better.


Hot sulfuric leach:
The H2SO4 with small additions of HNO3 (oxidizer) and heating basically is using sulfuric acid to dissolve base metals.

Cupric chloride leach:
HCl with small additions of oxygen or 3% H2O2 will dissolve copper iron and other base metals.

Ferric Chloride leach:
Ferric chloride and strong heating and high chloride concentration, works much faster (and vigorous) than the cupric leach above.
This is one leach I would consider.

I would consider laying the top hat on its side and smash it flat with a strong hammer blow.


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## anachronism (Oct 18, 2019)

Butcher why do people never mention an alkaline leach as an alternative to copper chloride?


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## snoman701 (Oct 18, 2019)

Iron is not passivated in nitric acid past about 55% or so...or less than around 40%.....and it is very temperature dependent. Those numbers are totally made up and drug out of my butthole....the sweet spot for passivating iron is around 50%ish (1 water mass : 2 hno3 67% mass) room temp or colder. That number is based on lots of experience as well as peer reviewed journal articles. Too concentrated or too dilute or too hot and you lose passivation and the reaction goes nuts. 

The hot nitric method to dissolve kovar top hats has been discussed before. The sulfuric helps keep the iron in solution, and likely also decreases passivation. 


Sent from my iPhone using Tapatalk


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## butcher (Oct 18, 2019)

What alkaline leaches are you referring to?

Like cyanide, thiosulfate, hypochlorous, and (leach...) ???
(Cyanide well then, that is just another topic altogether, with restrictions, availability, and dangers...)

Thiosulfate besides being limited to the types of Ore involved, and its many complications to run effectively.


With mineral ore's the alkaline leaches are more common and can be useful depending on the composition of the ore, but are less common with leaching, or more like etching of) the more elemental metals.

We have had a few discussions on the forum of these leaches.

https://goldrefiningforum.com/phpBB3/viewtopic.php?t=16292&start=20


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## g_axelsson (Oct 18, 2019)

You forgot about the alkaline copper chloride leach. :wink: 
Copper chloride dissolved in ammonia. It's popular for etching circuit boards on an industrial scale. Works really fast but is a bit smelly.

Göran


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## butcher (Oct 18, 2019)

I am not that familiar with that etching process. I have heard of it, what I understand is that if the leach is run correctly it would be good for etching copper traces for making circuit boards, I have not tried it but have heard it was smelly.
The fact that this leach is not that popular even as a copper etchant for making traces on circuit boards, can give us some clues of its difficulty and its effectiveness for use in the industry.

It does not seem to me to be much different than the cupric chloride leach except they are using an ammoniacal solution to complex the copper, not all base metals are amphoteric or will complex as easily into the ammonical complex.


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## Bertho (Oct 18, 2019)

I am sorry for adding confusion, there was a typo on my 17-Oct post.
After drying up, I added HCl, not nitric acid.
So in summary, the batch has been cooking for 4 days in hot HCl.
A couple of times I let it cool off and tried to add 10ml of sulfuric acid and a second time 20ml.
There is instant reaction for a couple of seconds and the sulfuric is gone.
Things are getting dissolved but extremely slowly.
What is most surprising to me is that the very skinny gold plated steel transistor and IC leads are in many cases untouched. Is the gold plating so good that it is protecting the steel?
I added a picture of a sample fished out and rinsed.
Bertho


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## anachronism (Oct 18, 2019)

Not quite so Richard.

Try Glycine in an alkali solution of Sodium Hydroxide and see how hungry it is for Copper. Cold not hot. When hot it also goes for Gold.


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## Bertho (Oct 18, 2019)

I got to change direction, this is not working using hot hydrochloric acid.
Some stuff got dissolved but other was never touched. For example, see the skinny gold IC leads in my previous picture.
I strained the liquid to catch undissolved parts and rinsed them with water to get rid of the old HCl and now they are ready for further processing.
Options?
Incinerate before proceeding?
Half strength nitric with or without sulfuric acid as mentioned?
Sulfuric acid with a "touch" of nitric as mentioned? What is a "touch"
AR directly?
Here is a picture from the filtered HCl:
Bertho


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## butcher (Oct 19, 2019)

Not quite so Richard.

Try Glycine in an alkali solution of Sodium Hydroxide and see how hungry it is for Copper. Cold not hot. When hot it also goes for Gold.

Yes, I am sure it is hungry for copper and other metals, although I do not see any viable reason for me to try it.


There are many etchants that are used with copper or copper-based alloys.
Some that seem to be more common like:
Ammonium hydroxide (often with persulfates)
Dichromate / H2SO4 with a dash of HCl
Ammonium hydroxide / 3% H2O2
KCN / H20
KCN/H2O2/NH4OH
ammonium persulfate/hydroxide
Persulfate hydroxide/cyanide


I do not have experience with these, so I cannot comment,( besides cyanide leaches), I have not seen much reason for me to learn more about using most of the caustic based etching processes.

Some leaches that may work well with copper may not work that well with other metals involved like iron...

Seems like I see more talk of the caustic etching with some of the more reactive metals like aluminum...

I am more familiar with the different acid based leaches like HNO3/H2O, FeCl3/HCl, CuSo4/HCl, H3PO4/H2O2, CuCl2.


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## Bertho (Oct 19, 2019)

Update:
After draining and rinsing off the old acid I proceeded using AR gradually adding HNO3 on a hotplate. The AR temperature was 90C. I also rinsed off the content from the previous filtering operation into the beaker.
It progressed rather quickly, maybe an hour or so since I let it slow down before adding more nitric.
I let it cool off a little and then added some water and filtered.
Great success! All the steel was gone. See the 2nd picture.
What was surprising after all the initial problems was that the little feedthrough glass tubes had been completely etched out. The same thing with the ceramic IC headers. The holes are empty.

Basically the only leftovers are ceramic and glass plus some TO-92 plastic body transistors

I cemented out the gold and I am waiting for it to settle overnight.
Bertho


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## Bertho (Oct 21, 2019)

Another update:
After multiple rinses and then twice HCl boiling, drying, and melting I got a nice little bead 1.07g.
The yield was 1.2%.

Next batch (the rest in the box) I will incinerate first and then go directly to AR. I spent way too much time with the previous process.

By the way, what is the proper way: Edit my previous post or add a new one like this?
Bertho


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## FrugalRefiner (Oct 21, 2019)

Adding a new post is preferable. If you go back and edit a previous post, those following the thread are not alerted that a previous post has been edited, so they will probably miss the edit. Also, when you edit an old post, it can make posts that were made in response to an original post seem to not make sense.

Dave


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## MGH (Oct 21, 2019)

By the way Bertho, thanks for posting. I have a small amount of mixed components similar to this. I figured the yield would be something similar to what you are reporting here. It's nice to see your process and yield - helps me decide if/when to process what I have in hand.

Thanks again,
Matt


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## johnny309 (Oct 25, 2019)

Bertho said:


> Another update:
> After multiple rinses and then twice HCl boiling, drying, and melting I got a nice little bead 1.07g.
> The yield was 1.2%.
> 
> ...


 

Proper way is .......:
1. Incinerate...... because of varnish,some plastic leg spacers 
2. AR work best....and some heat will be better.....another option is CN.
3. This is my favorite......but is optional.....is flattening with an hammer.... because of sorting (white paste should appear...is Ge transistor)


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## Bertho (Oct 31, 2019)

After a lot of headaches I have processed the materiel in box in the first picture at the top of this thread.
I am very happy with the result: 8.8g = 1.3% yield.

There got to be better ways to do this when there is a very mixed batch. In the first place I am learning, so a lot of my headaches are presumably caused by me.

A quick summary: (Remember that there was a lot of steel in the mixture)
I tried a small test batch with half strength nitric and had many problems with sludge. I strained out the partially processed material, repeated the process, and finally dissolved the reminder in AR.

For the main batch I tried AR to start with. I added 300ml HCl to cover the parts and then gradually I added HNO3 to control the reaction. By the time I had added HNO3 to be the 4:1 ratio and there was no more action, even hot, presumably all the AR was used up. Only minor sludge at that point.
I figured to add more AR gradually so as before, I added just 100ml HCL this time to be followed by HNO3.

Instantly lot of reaction! A very thick yellowish/brownish foam was formed and I had to add ice to the outside of the 2l beaker to slow it down. The foam was thick like whip cream and I had to spoon it out. See picture. It also instantly formed a super-fine sludge. I again strained out the partially dissolved material and let the liquid & sludge sit overnight. See picture.
Next day I rinsed the parts and then this time slowly proceeded with pre-mixed AR.

I could not filter the previous liquid because of the sludge, so I strained it through a very fine stainless steel wire mesh and caught the gold flakes that had peeled off in the early processes and added them to the AR.
I finally dropped out the gold and after multiple rinses and boiling HCl, I melted it.
I do not understand why I all of a sudden got so much foam and sludge when adding the extra HCl.


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## anachronism (Nov 1, 2019)

There's one question I would ask. Why after 5 years on the forum were you mixing 4:1 AR? 

I'm glad you got there in the end- well done however can you let me know- given that it's written everywhere that you shouldn't do it.


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## MGH (Nov 1, 2019)

Jon, I don't think he's saying he pre-mixed the AR.


Bertho said:


> ...
> For the main batch I tried AR to start with. I added 300ml HCl to cover the parts and then gradually I added HNO3 to control the reaction. By the time I had added HNO3 to be the 4:1 ratio and there was no more action, even hot, presumably all the AR was used up.
> ...


I think he's just noting that by the time the reaction stopped, it ended up being a 4:1 ratio.

Bertho,
To answer your question, I think the same thing has happened to me before too. Here's what I think happens:
- Especially with a mixture of solids as in this case, it's possible that the initial HCl was already consumed.
- Adding nitric incrementally does continue to dissolve some metals - as it would with or without HCl.
- Eventually you end up with an excess of nitric, even if only a little bit.
- Also, through this process with a mixture of metals, gold has been dissolving and re-cementing throughout. You now have finely divided gold solids AND some excess nitric.
- Upon addition of a large amount of HCl, that finely divided gold can now easily dissolve, producing lots of gas and bubbles very quickly.
- The foam is just a by-product of all the other "trash" present in the type of material you were processing.

This doesn't mean your process doesn't work. It's pretty much the way I would do it. It just means you need to be careful when adding more HCl to a mixture to which you've already been adding nitric.

Hope that helps,
Matt


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## anachronism (Nov 1, 2019)

Matt I think he was adding Nitric to take it to the 4:1 ratio. But either way your point about adding HCl to an AR solution that's stopped working:

When doing these heavy iron based products you often end up using the HCl first, because of the nature of the beast. The warning sign that it's used up tends to be the solution going cloudy as the metals start to drop out. I agree with what you said- it's all about being careful adding it. That given its not quite as bad or violent as adding Nitric to a solution that's run out of Nitric. That stings a bit when it erupts. 

Jon


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## Bertho (Nov 2, 2019)

Just to clarify:
For pass #1 I added the HCl first and then gradually added nitric.

When the reaction stopped I was going to do the same thing again but I got the surprise foam generation as soon as I added the HCl.
The explanation for the eruption makes sense since it was a gradual process and presumably a significant portion of the HCl got used up early so there ended up being too much nitric.

After that big surprise eruption I tried to play it safe by gradually adding premixed AR.

This brings another question: How can I dissolve the sludge so I can filter the liquid to catch any gold particles that has already dropped out and now are mixed with the sludge?
Bertho


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## nickvc (Nov 2, 2019)

With your sludge I’d add Hcl slowly until you get no further reaction then add nitric in small increments to avoid boil overs, if after an addition of nitric you get no reaction add a little Hcl and watch for any further reaction.


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## Bertho (Nov 4, 2019)

Thanks to all the persons helping with suggestion.
I am off to do the next project: Sulfuric cell de-plating.
Bertho


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## Williamjf77 (Nov 8, 2019)

be on the lookout for any ua726 metal can, 10 pin I think when doing lots of stuff like that. Even lm149,249,349

Audiophool gold they go for 100$ a piece for the 726


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## Bertho (Nov 10, 2019)

Thank you for the tip Williamjf77
Bertho


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## Williamjf77 (Nov 10, 2019)

There are a lot of audio type transistors and amplifiers that are pretty sought after in that world. Not all are audio specific. I think the ua726 is an exponential amplifier. Every time I see a pile of metal cans I think about it. Any part starting with SSM also would be a good score. The CA3080 is one I’ve found in scrap in a metal can, worth about 10-20$ used in vintage audio but they were used elsewhere besides audio.

I used to be into building audio gear and the vintage analog sound seems to always be popular.


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## johnny309 (Feb 16, 2020)

Bertho said:


> I could not filter the previous liquid because of the sludge, so I strained it through a very fine stainless steel wire mesh and caught the gold flakes that had peeled off in the early processes and added them to the AR.
> I finally dropped out the gold and after multiple rinses and boiling HCl, I melted it.
> I do not understand why I all of a sudden got so much foam and sludge when adding the extra HCl.



The "foam" can be an result of thermal paste compound reacting with HCl( ZnO main component).You should add HCl in small increments because you got an heated reaction going. That is why i told you to hit them with an hammer as an sorting method.


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## johnny309 (Feb 16, 2020)

Williamjf77 said:


> There are a lot of audio type transistors and amplifiers that are pretty sought after in that world. Not all are audio specific. I think the ua726 is an exponential amplifier. Every time I see a pile of metal cans I think about it. Any part starting with SSM also would be a good score. The CA3080 is one I’ve found in scrap in a metal can, worth about 10-20$ used in vintage audio but they were used elsewhere besides audio.
> 
> I used to be into building audio gear and the vintage analog sound seems to always be popular.



If you are interesed...of an couple of hundred pieces,write me an email......I do not live 2000 years to sell one piece a month for "museum artist"....just metal to metal.


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## Geo (Feb 16, 2020)

TO transistor packages. All contain lithium grease or heat conductive paste. That's what created the foam. You have to roast them until all of the package is red hot. Be careful as they can pop throwing pieces in all directions so it's best to cover when roasting. I found that poor man's nitric acid works a treat for these particular items. Even though the parts are magnetic, the legs are Kovar and the top is high nickel stainless steel hence they are magnetic. The can lay on the ground for years and never rust. HCl is a poor choice for removing the iron based part of these items. They normally do exceptionally well by weight. The only exception is TO-3 package. It is basically a honking big chunk of copper with a magnetic cap. Some are completely gold plated inside and out and some have a very thin gold plating that gives it a yellowish tint and some are not plated at all. All of the TO-5 packages will have some gold bonding wires that are much thicker than IC packages.


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