Gold plated steel ICs and transistors

[Bertho]

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

 

[butcher]

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.

 

[Bertho]

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

 

[Bertho]

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

 

[FrugalRefiner]

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

 

[MGH]

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

 

[johnny309]

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

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)

 

[Bertho]

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.

 

[anachronism]

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.

 

[MGH]

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

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

 

[anachronism]

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

 

[Bertho]

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

 

[nickvc]

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.

 

[Bertho]

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

 

[Williamjf77]

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

 

[Bertho]

Thank you for the tip Williamjf77
Bertho

 

[Williamjf77]

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.

 

[johnny309]

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.

 

[johnny309]

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.

 

[Geo]

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.