what is old clear thermal grease?

[coppercone2]

So some old stuff that has say, germanium TO transistors on it, has a clear greasy compound ranging from liquidy to slightly grease on it when you remove the thermal pad. There is no filler in there.

For the sake of curiosity, what is this? Just some like silicone oil or silicone grease (similar to dielectric grease?)

[cantata.tech]

For the sake of curiosity, what is this? Just some like silicone oil or silicone grease (similar to dielectric grease?)

Most likely yes.

[Psi]

Just watch out for white powder and crystals on the outside of old metal can transistors.

It can be very toxic and give you a splitting headache within minutes, or possibly worse.

[coppercone2]

? did they just.. like add BeO powder to act as a thermal improvement thing?

[Psi]

I'm referring to when the transistor leaks stuff from inside, which can happen on metal can transistors when they get old.

Not sure what it is exactly, but its not pleasant.

[coppercone2]

have you seen this happen with a transistor that still works? It kind of sounds like that transistor would be toast. Like internal shorts at least.

Well usually I have like 500 dirty q-tips to throw out after I clean those kinds of things, makes me feel better that I am not wasting them lol. I try to avoid touching that kind of shady crap in general. And I am not stingy about reusing the ultrasonic cleaner water to save soap. But I will keep an eye out. I usually don't work on soldering stuff until I clean it, its just a much more pleasant experience. I usually think stuff like that kinda stuff might be old capacitor fluid, dripped batteries, corrosion.. kinda paranoid about cadmium also when I work on stuff. And I try to generally clean up stuff a little before dip cleaning because dirty ass water going all over the PCB is not great either.

Actually I never felt better about using all those q-tips, after a while I was thinking if I was being wasteful. Guess not, better not to contact unknown substances. Sometimes I was like oh should I just get a paper towel..... does not pay to be a cheap skate about cleaning

[amyk]

Just watch out for white powder and crystals on the outside of old metal can transistors.

It can be very toxic and give you a splitting headache within minutes, or possibly worse.

That's possibly from oxidation of cadmium plating.

[Doctorandus_P]

The further back you go, the more potentially dangerous stuff you'll find, so be careful with old stuff.

A few hundred years ago people had wallpaper drenched in arsenic. It was good stuff for keeping bugs out of your house.
Nellie Kershaw was the first fully documented "Death by Asbestos Poisoning" https://en.wikipedia.org/wiki/Nellie_Kershaw She died in 1924, and it took many years before health issues got the better over commercial interests and the stuff started to be phased out.

When I was young, I heard that "old heatsink paste" was "very unhealthy", and I would not be surprised if thermal paste from the '60-ies or older would contain Beryllium oxide powder.

[factory]

So some old stuff that has say, germanium TO transistors on it, has a clear greasy compound ranging from liquidy to slightly grease on it when you remove the thermal pad. There is no filler in there.

For the sake of curiosity, what is this? Just some like silicone oil or silicone grease (similar to dielectric grease?)

From two random manuals from HP/Tek....





If it's not clear then it's something else.

Another nasty one is dissimilar metal compound containing zinc chromate, but that's a yellow color.
Glad I got rid of that stuff from work. https://www.jointingtech.co.uk/Download/Unial%20Jointing%20Paste.pdf

David

[Psi]

Just watch out for white powder and crystals on the outside of old metal can transistors.

It can be very toxic and give you a splitting headache within minutes, or possibly worse.

That's possibly from oxidation of cadmium plating.

yep, looks like cadmium oxide is toxic and can cause a headache so that is highly likely when happened in my case.

Headache was literally within a minute of handling the transistors and came on very strong all of a sudden, not like a normal headache that slowly appears (atleast for me).