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Registered Member #89
Joined: Thu Feb 09 2006, 02:40PM
Location: Zadar, Croatia
Posts: 3145
I don't know if berylium oxide was very common, and it looks that it can hardly get powdered in semiconductors. I only saw it once actually, there was a warning in a RF mosfet datasheet. It was solid part of case.
If powdered and in bigger quantities it can be very dangerous altough.
Registered Member #27
Joined: Fri Feb 03 2006, 02:20AM
Location: Hyperborea
Posts: 2058
I have heard about people cutting the cover off with a hack saw which then converts it to a phototransistor. Not sure how useful this makeshift phototransitor would be but probably another "interesting" project to try.
The transistors and LEDs I have tested have been quite efficient, comparable to a solar cell. I have managed to get several mA from different dies. Even from a LED with a tiny die where the package focused the light on the die.
Maybe put some clear epoxy over the die to protect it.
The last 3055 I opened had the die covered with some resin like substance.
Registered Member #30
Joined: Fri Feb 03 2006, 10:52AM
Location: Glasgow, Scotland
Posts: 6706
Beryllium oxide is only in specialized RF power transistors as far as I know. It's too expensive for crappy 2N3055s
My old ham radio club once tried to replace blown trannies in a 144MHz power amp. In the process of getting the old ones out, we managed to shatter one and scatter little pieces of BeO around the room. :-o We all lived to tell the tale though with no ill effects whatsoever. BeO really doesn't seem to be so dangerous, unless you grind it and then inhale the dust or ingest it in some other way, like cutting yourself on a broken piece of it.
I've never blown a hole in a TO-3, although I'm working on a 400w audio amp project, so it's only a matter of time. >_<
Registered Member #56
Joined: Thu Feb 09 2006, 05:02AM
Location: Southern Califorina, USA
Posts: 2445
Funny BeO should come up... Back my my dad's younger years he used to work at Rockwell working on various projects one of which involved machining parts of a gyroscope out of Be. But there was a bake process to clean off any residue from the Be, so they would put the pieces in a vacuum oven overnight. So of course one night the oven got a crack and came up to pressure leaving a fine BeO powder for them the next day They just decided to bag that oven up and use a different one.
But unless it is powdered you shouldn't have to worry about it... Oh, it is powdered, you are screwed
Could be anything really, I have opened 3055's up, and there isn't any BeO. Unless you got a some rebranded good transistor... I would guess that is the silicone? that they put in the die to protect it that got really hot in there...
Registered Member #33
Joined: Sat Feb 04 2006, 01:31PM
Location: Norway
Posts: 971
I once opened some old germanium transistors in TO-3 package. They were filled with a white powder. I am quite sure it's not berrylium oxide, as it would be useless if used in this way. BeO is used to electrically isolate the transistor from the case while still having good thermal contact. In TO-3 devices, the die is directly bond to the package, so the BeO would offer no advantage.
Registered Member #89
Joined: Thu Feb 09 2006, 02:40PM
Location: Zadar, Croatia
Posts: 3145
Regarding cost, small amounts of beO don't seem to be that horribly expensive. I looked around a bit for that. Factory techniques and low inductance/capacitance design is what usually makes such transistors expensive, availability and usage also.
I recently found a transistor available in our shop, bly89c wich conains BeO. It costs 30kn wich is about 3-4 $.
Anyway we'r getting away from blowing-3055's topic
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Blew a hole through a 2n3055
They just decided to bag that oven up and use a different one.
