Wanted TO-247 Beryllium Oxide pads

[dshortt9]

I would like about 25 for a Pass Aleph 2 project.
dshortt@wi.rr.com

[P.Lacombe]

Don't make pollution worse ! Beryllium Oxide is very toxic.
Use mica pads, with a little silicon grease. Works very fine.

Regards, P.Lacombe.

[cocolino]

Use mica pads, with a little silicon grease. Works very fine.

Or even somewhat better regarding termic conductivity: Kapton pads

[AudioFreak]

I dont feel like an argument here but when all things are considered, mica is the best for TO-247/TO-3P devices.

[grataku]

dshort
are you building a nuclear reactor or an amp?
If it was thermally conductive, would you use something like asbestos for your transistor pads? BeO has pretty much the same effects on your health as asbestos.
Before you use funky materials in your stereo take a look at their material safety data sheet (MSDS), they are all over the web.

[P.Lacombe]

Christoph,

The most important : surfaces and isolating pad must be perfectly plane and surgically clean. Use pure silicon grease, not compound which is too pasty. Mica or Kapton works well...

Regards, P.Lacombe

[dshortt9]

grataku,

OK, I may be overdoing it. I'll stick with mica. I work in a factory that made machined beryllium parts for the space program and also have worked for the worlds largest supplier of rare earth and inorganic chemicals so I'm well aware of the hazards of beryllia. BUT, Thanks for the warning anyway. I'm sure the majority of people are unaware of the dangers involved.

[Peter Daniel]

I was under the impression that BO pads were the best around and that's why I'm using them exlusively. When handled properly I don't think they create much danger, at least I wouldn't compare them to asbestos which has totally different material structure (they still use asbestos in aerospace industry).
I like that Forum, because I'm always learning something new.

[Claus]

You should not use Beryllium Oxide at all.

BeO
Extremely toxic by inhalation and ingestion. Typical LD50s for beryllium compounds are between 0.5 and 5 mg/kg. Probable human carcinogen. Serious respiratory irritant. May be harmful by skin contact.

KCN (Potassium Cyanide)
LD50 oral 5 mg/kg

LD50:
"The Lethal Dose 50 (LD50) test involves the administration of a substance to a group of animals at increasing doses in order to determine the dose that kills 50 percent of the test subjects within a set time frame."

Get my drift.

Claus

[sam9]

I used to work for company that used Beryllium Oxide. Yes, it's dangerous and probably not for the DIYer, but it isn't the work of the devil either. We complied with OSHA and EPA in using it. A solid piece of it is pretty harmless. You can touch it it without fear if it is clean, as in dust free. Its a ceramic and the danger comes if you break it. That releases ihaleable ingestible dust. Worse is if you cut it - lots of dust. Obviously, using in in fabrication requires precautions and ways of containing the dust. Not diffucult in a production situation. Not practicle in your garage.

Once included in the final assembly of a product its inert. Later disposal is a problem because breaking, cutting or crushing release dust from it. I don't recall for sure, but I don't think burial was a problem since it doesn't tend to leach out - just sit where you left it.

In short not something to mess with, but certainly far from being in the same category as nuclear waste.

That was 10+ years ago, so maybe more is known now.