Removing the "Hat" from TOPHAT Transistors; Chemical saving method.

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Mar 19, 2021
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This is something I do while watching TV. Most of the American made, Motorola and other transistors I've processed have been hollow. Some of these have molecular sieve which is powdered desiccant (thought to be inert), or may contain some kind of thermal paste. The process will also work for them but it's a bit messier and you may not want to do it on the sofa.
By removing the hats on these transistors less chemicals will be used regardless of the leaching process used. I also sometimes cut the legs at the base of these when it is clear they are thickly plated and made of very stiff Kovar material. I hope this helps someone as much as it's helped me after I developed the method.
Processing Tophat transistors
 
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Crazy how much top hat info has come out the last several days.

How do you guys deal with the thermal paste? All of these have thermal paste so I’ve set them aside.
I would run some test batches with different solvents, and find something that works to dissolve the paste. I haven't processed any yet with paste but that was my idea for when it eventually occurs. After using solvents of any kind, I would then use strong detergent to rid the material of solvents and then rinse them many times before adding any acids to begin the recovery process. Unless I find information here on the forum addressing this specific issue, this is the route I will take.
 
Another good technique is to use bench shear. Only limitation are transistors themselves :D if you once have these tinned bastards like I do, game over :D
I heard about guy who setup a DIY apparatus for sawing the majority of the hat off with band saw.

I know that it is saving like 30-40% of the waste... But I simply does not have the time needed. And patience needed. If the ones I do were easy like the ones you process, I would happily do them all.

Only ones which I have on regular basis and could essentially be decapped are old soviet USSR made ones. Soviets made the top hat differently, and usually from nickel plated copper. Also, they didn´t soldered the hats, so they can be removed by squishing them - exactly as you do it.
 
Crazy how much top hat info has come out the last several days.

How do you guys deal with the thermal paste? All of these have thermal paste so I’ve set them aside.
Be careful about old stuff with thermal paste or oil inside. Good chance that oil or grease contain PCBs - at least here in former soviet countries, all old oil-filled capacitors, transformer oil, and also paste inside Ge transistors contain PCBs... But I think western countries does no better about PCBs in electronics from that "PCB era" :D

If the paste isn´t silicone, it would dissolve in standard solvents like toluene, xylene, or acetone. Probably also in kerosene if it is PCB one :D If it is silicone... That would be tough. Maybe burning it off would help - but beware of fuming silica dust that creates when you burn silicones.
 
I recall someone saying they incinerate the transistors which contain the grease, and the pressure which builds up inside them pops the caps open. Even if they’re still attached, a gap would at least make them easier to peel apart, so would kill two birds with one stone. It sounds plausible I guess but you’d have to try it to see if it works and how well? As far as chemical treatment some silicon compounds are attacked by Lye. If you have some uncapped you might try boiling them in hot Lye (sodium hydroxide) solution, like you’d do for removing solder mask from boards. Be very cautious! Besides being extremely caustic Lye also attacks aluminum and even glass containers, so you should heat it in stainless steel pan. I’ve also heard just boiling them with hot water suggested. IF the grease liquefies and floats to the surface it would be one method of separating most of it, but then it would still require incineration to remove any remaining coating before processing.
 
Crazy how much top hat info has come out the last several days.

How do you guys deal with the thermal paste? All of these have thermal paste so I’ve set them aside.
Hi Ohiogoldfever,,

Do you mean, these transistors do have thermal paste inside?

Would you process them including the tin/solder on the pins and with the blue plastic spacers attached?
 
I recall someone saying they incinerate the transistors which contain the grease, and the pressure which builds up inside them pops the caps open. Even if they’re still attached, a gap would at least make them easier to peel apart, so would kill two birds with one stone. It sounds plausible I guess but you’d have to try it to see if it works and how well? As far as chemical treatment some silicon compounds are attacked by Lye. If you have some uncapped you might try boiling them in hot Lye (sodium hydroxide) solution, like you’d do for removing solder mask from boards. Be very cautious! Besides being extremely caustic Lye also attacks aluminum and even glass containers, so you should heat it in stainless steel pan. I’ve also heard just boiling them with hot water suggested. IF the grease liquefies and floats to the surface it would be one method of separating most of it, but then it would still require incineration to remove any remaining coating before processing.
Yeah, popping them is commonly done, but you need to be prepared for relatively vigorous "explosions" - so use good and thick walled steel container with heavy lid, loosely covering the contents of the pot - not to create closed system. And of course, you need to do it somewhere far away from people - otherwise you can catch some unwanted "attention" :D

Also, be prepared that upon explosion, the superheated grease could catch fire. And burning silicone gives off fuming silica dust, which is very very bad to inhale (cause silicosis very quickly). And when this is some regular grease, be prepared for eventual PCBs in the air - as they burn very poorly (intended use as fire retardants) and mostly came out as unbearable nasty smoke :) Very bad for health. And if they also eventually catch fire, all chlorinated compounds give off HCL during burning process, so be prepared for HCL mist crawling out of the steel container, that will become significantly rusty after the procedure :)

Boiling them in hydroxide is doable, and mostly I much more like the idea of liquifying the grease and let it float to the surface of the liquid. This technique is superior, whenever it is possible to use it :)

Here, some folks proceed with "popping" method when processing the silver or iron-silver tantalum capacitors. This is somewhat less corrosive and nasty, as acid present inside is sulfuric acid, but all in all, sulfuric mist is always produced during the process. But the bad thing is that explosions of these are powerful and loud - like shooting from shotgun :D I personally cannot do this - I do not have any place where I can deliberaty "shoot" them open :D People here aren´t used for hearing any noise that resembles shooting - so 100% assured, some police patrol will came to handcuff me for alleged shooting in public :D and when they find out no guns are present, they start asking question about what the heck I am doing...

Alternatively, you can etch the top hats off with straight HCL and heating. This will not cut the consumption of acids, but you will kill two birds with one stone - remove the hats and also liquify the grease which will float to the top :)

Proceed with great caution. Be safe.
 
Hi Ohiogoldfever,,

Do you mean, these transistors do have thermal paste inside?

Would you process them including the tin/solder on the pins and with the blue plastic spacers attached?

Most of what’s in the bowl has thermal paste in it. They ended up here directly from the boards so they have not been cleaned in any way.

My plan was to use a large stir rod in a bucket of soapy water to clean the cans (came from a greasy machine control) and hopefully knock the plastic stand off loose of the transistor. Floating to the top.

Like my others I would just dump them into AP and wait but haven’t done so for fear of making a huge mess once the paste is liberated from the caps.

Your thoughts are welcome.
 
I'd pull the blue spacer by hand (annoying, but I know, it works).

Until now, I had to deal with thermal paste on CPUs and larger transistors only.

I've got no clue for the thermal paste inside the transistors.
As orvi and macfixer01 suggest:
Open a few and treat them with solvents, acids, lye,… and a good prayer. 😉
 
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