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Wanted TO-247 Beryllium Oxide pads

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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.

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.
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. ;)
You should not use Beryllium Oxide at all.

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

"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.


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.

Well, I could not help myshelf arguing on asbestos!
Did u all know that less than 10 years ago all of us were poluting our beloved earth using brake pads containing lots of asbestos?
Not to our knowledge though, but the ones who did the decision making, decided that asbestos is no good for brake pads just 10 years ago...

I use berrylium dioxide insulators in my aleph30 and these are the best ever tried(salvaged from an old UPS), but u can order also aluminium oxide insulators with comparable performance and more user friendly.
Moreover, BeO2 insulators are safe enough, provided u use plastic gloves and that u do not swallow or breaking them, as toxic is only their dust. For the ones who cannot access such materials mica are very, very good, too.


Well, I cannot help myself arguing about it too, when I hear cries of danger from others who did not experience it but only heard about it.
I handle all my BO pads without gloves. Once I even tried to trim one on a belt sander but it was too hard so I stopped (of course it was before I read all about its danger on a Forum). Basicly, its ceramic like and there is no dust coming from it.
Neverthereless, I have never experienced any harmful effects and I will continue to use it.
Panos and Hpotter in no particular order...
it's BeO or beryllia, not BeO2. You can make BeO2 or Be2O or other gasous variations by laser ablation of the BeO ceramic but I don't suggest you breath the vapor byproducts. Under normal conditions it's hard for a group II element to have a +4 or +1 oxidation state.
Anyways, asbestos made GREAT brake pads far superior to whatever they are using today, however, it is also true that for auto mechanics that have worked in the asbestos era the incidence of lung cancer is much higher than in the normal population, though it's also true that mechanics smoke like mother****ers.
Dust maybe hard to see with the naked eye and cancer is one of those pesky things you may not experience for years to come. Do you really want to take the chance?
What is the fixation with beryllia? Did you actually measure the difference in transistor temperature and heatsink temperature with a beryllia insulator and compared it to a mica insulator with silicon-zinc grease? Do the trannies run cooler with the beryllia pad? How much cooler?
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