TO3 transistor ceramic insulators

[Reid Malenfant]

I have just bought rather a few TO3 ceramic insulators, these are vastly superior to either mica or the rubbery type (sorry i'm not sure what they are :eyebrows:). They conduct heat better & at a couple of mm thick they'll have much better insulation properties as well as less capacitance to any heatsink.

While i'm going to need quite a few myself there will probably be about 100 spare (i bought 300 :eek:), now assuming they get here they are up for grabs by anyone that is doing repairs to equipment that uses TO3 transistors or for that matter making their own kit ;)

The last lot i ordered from this chap got lost at his local airport (this was about a year ago), but he fully refunded me. I figured i'd have another crack at it & see what happens so fingers crossed :eyebrows:

So if anyone wants some then as long as you cover postage you can have some for a grand total of nothing ;) Just don't ask for the lot :punch:

I'll reply on this thread if/when they arrive & then feel free to grab some :cool:



Don't ask what i want nearly 200 TO3 insulators for, you'll find out eventually :ner:

Here is what i'm talking about...
2977

E2A:- This offer (once i receive them) will be open to regular posters on this forum only, please don't think you can join & get some free insulators :rolleyes:

[Rare Bird]

Hi Mark
Yes please i'm gonna need some for my amp, can you give me some details of what exactly they are spec wise.

[StanleyB]

Hi Mark
Yes please i'm gonna need some for my amp, can you give me some details of what exactly they are spec wise.
TO3 ceramic insulators?

[Reid Malenfant]

Well they are advertised as ceramic, frankly it's cobblers :eyebrows: As far as i know they are Aluminium Oxide, though they could be something else..

It looks like ceramic that's for sure, i have a load here for TO3P transistors & it's a typical white ceramic colour so i guess that's where people get mixed up :scratch:

[spendorman]

Thought so, but I had to look at this to check

http://en.wikipedia.org/wiki/Aluminium_oxide

[Reid Malenfant]

Hi Mark
Yes please i'm gonna need some for my amp, can you give me some details of what exactly they are spec wise.
Check the link below ;)

Thought so, but I had to look at this to check

http://en.wikipedia.org/wiki/Aluminium_oxide
Cheers for the link :)

Well the chap has despatched them, lets see if they get further than Sofia airport this time :eyebrows:

I'll let you know if/when the arrive Andr'e :)

[StanleyB]

Aluminium oxide would conduct electricity. Ceramic wouldn't.

[Reid Malenfant]

Aluminium oxide would conduct electricity. Ceramic wouldn't.
Aluminium Oxide is non conductive which is why it's used as an insulator for power transistors, it also has very high thermal conductivity which kind of helps ;)

[StanleyB]

Aluminium is extracted from the oxide by passing electricity through it.

[Reid Malenfant]

Stanley, please take a look at the Wiki page ;)


Aluminum oxide is an electrical insulator but has a relatively high thermal conductivity (30 Wm−1K−1[4]) for a ceramic material.
Now don't forget that this stuff has been formed into slabs a few mm thick, i'm not sure how i'll be honest.

Perhaps if you stuck a few 10s of KV accross the thing at very high current it might smelt the stuff into Aluminium, but it won't conduct at all with up to 400V DC accross the stuff :)

I know as i used to use them in SMPS & more specifically on the switching mosfet & catching diode used on power factor correction units. The Mosfet & diode were each mounted using one of these aluminium oxide insulators along with thermal compound & this was clamped to an aluminium chassis, no leakage took place :)

I'm also trying to remember what the flash test voltage was that was used between mains input & the chassis, but whatever it was there was again no leakage ;)

[spendorman]

Main trouble with thin alumina is cracking. I hated working with the stuff.

[Rare Bird]

Actually i've always found Silicon greaseless washers fine as long as you don't over tighten the transistor onto the sink.

[Reid Malenfant]

Indeed, me to ;) However, if you can pick up something better electrically & thermally for the same price it's a bit of a no brainer :eyebrows:

No problem re-using them either as they are solid :)

[Glen B]

I have just bought rather a few TO3 ceramic insulators, these are vastly superior to either mica or the rubbery type (sorry i'm not sure what they are :eyebrows:).

FWIW, the rubbery types are called silpads. The material is silicone based. :)

[Reid Malenfant]

Yep, cheers Glen ;) I could never remember the name of the things but earlier i went looking about at RS Components & Farnell & there it was :eyebrows: I still couldn't find any Aluminium Oxide insulators though which is what i was looking for :lol:

[Reid Malenfant]

Andr'e, perhaps you'll let me know how many of these insulators you require as they arrived this morning :) I honestly didn't think it could mess up twice in a row & i was proved right :eyebrows:

PM me your address & i'll get them out to you next week ;)

[Reid Malenfant]

PM me your address & i'll get them out to you next week ;)
:lolsign: You'll have a difficult time PM'ing me your AD with your PMs switched off, i just tried sending you a message & the computer (well the forum actually) says NO! :eyebrows:

Ah well.... 3039

[Alex_UK]

Andre's not been around for the best part of a week, either a holiday or a sabbatical - either way, hopefully not too long before the prodigal (or should that be progidal) returns... :lol:

[Marco]

'Sabbatical', I think - although he was last logged in on Wednesday.......

Marco.

[Reid Malenfant]

'Sabbatical', I think - although he was last logged in on Wednesday.......

Marco.
Not a problem, they'll still be here when Andr'e returns :)

[Rare Bird]

Thanks mark
I'll not be needing em now..

[Rare Bird]

'Sabbatical', I think - although he was last logged in on Wednesday.......

Marco.

I've tried leaving this place tbh, i've given it another go this last two days but no good, i really must go this time.

[Reid Malenfant]

Thanks mark
I'll not be needing em now..
Are you sure Andr'e? I'll post them FOC chap if you have a use for them ;)

I've tried leaving this place tbh, i've given it another go this last two days but no good, i really must go this time.
:scratch: You lost me??? :confused:

[Rare Bird]

Thanks Mark but it's ok i used silpads

[Reid Malenfant]

Thanks Mark but it's ok i used silpads
Ok chap, if you need any in future just ask :) If i have spares then they are yours ;) Doesn't appear to be a lot of takers right now, no doubt everyone prefers these japanese transistors like MT200 & whatever the 2SC5200 happens to be...

Give me a metal case any day :eyebrows: TO3 rules :p

[Rare Bird]

Give me a metal case any day :eyebrows: TO3 rules :p

Too right