looking for a transistor

METAL CAN 2N2222s ? The metal can is part of the JEDEC spec for the part. It's not optional. Do you mean plastic encapsulated PN2222s ? I still wouldn't use those because beta is quite low compared to modern parts.

Graham

Yep. In every package style currently in use for sm signal devices.

Anything else is NOT a *** 2N2222 ***. It will have a different part number.

Graham

Eeyore wrote in news: snipped-for-privacy@hotmail.com:

When I pointed out the radiation aspect, John Popelish pointed out that it is a small part, not significant, and when the Popelfish has translated things electronical, I tend to listen. You're right about the second part though, compared to the copper tab formed as a single part with one of the leads, the thermal conductivity between can and wires is lower. I doubt it's that much lower though.

The die on the TO-18 is attached to the base of the can... with a thermally conductive epoxy.

Wanna buy some stock in a stable, not going anywhere any time soon company? Look at the makers of EpoTEK epoxies. They are what the industry uses to "glue down" dies to various substrates. I use a very expensive silver filled variety at work to seal up chassis so they have a lower EMI radiance, even though it is meant for die attach.

Silver is like $14 an ounce, but the micro-fine silver powders they use in these media are VERY expensive. Far more than $14 an ounce.

So a one pound epoxy kit costs several hundred dollars.

innews: snipped-for-privacy@hotmail.com:

It is fairly likely that the leadframe makes more difference than the metal vs plastic housing. The transistor substrate isn't all them well connected in either thermally. The plastic part ends up having a lower junction to case thermal resistance than the metal one. I suspect that this is due to the heat flowing down the lead frame.

TO-92 still outperforms TO-18 for heat transfer from junction to ambient..

Graham

Graham

SMT

Japanese

for

audio apps

IME) are

Western designs? Are we on the road of bashing the US again ?

What the hell does Western have to do with it?

I agree. The 2N2222 parts have Kovar or some other iron alloy leads (gold plated, perhaps) of very low thermal conductivity, compared to copper, and for the base and emitter mounted in the can with glass seals. The collector lead is welded to the can, but the alloy is still the same low conductivity stuff the other two leads are made of. The chip wire bonded to the base and emitter leads, so those don't even have much of a thermal connection to the die inside the can. Many TO-92 parts have punched copper lead frames, especially the Zetex E-line, with the die mounted directly on a flag on the collector lead. Solder that lead to a large area pad on the board, with a short lead length, and you carry away more heat than all 3 leads of the metal can might carry. Plus the thermally conductivity epoxy carries heat off all the surfaces of the die not bonded to the collector tab, where the 2N2222 has the die in an otherwise empty can, so only the collector side has a local heat sink.

IME) are

US or European.

Slow bipolar power transistors. Don't ask me why but Motorola and RCA never could match Toshiba or Sanken for device speed combined with good SOA.

Graham

Eeyore wrote in news: snipped-for-privacy@hotmail.com:

It's not exactly an order of magnitude, is it? If the thermal resistance between can and chip were that much greater, I think the Pd difference would also be greater than that.

Toshiba IME) are

could match

The TIP35 also had a very bad dynamic saturation characteristic. When the collector voltage got below about 2V, they slowed down to a crawl.

No it's not that much but it is the precise reverse of what the resident FOOL claimed.

Graham

I think it is even worse than Brass. Some TO-92 transistors are magnetic some aren't. I suspect that some are made with covar lead frames because the companies are used to working with the stuff.

You can solder it to a metal post to do even better. I've seen this done in an audio amplifier. The TO-92s were soldered onto a 0.025 inch square post that stood up some distance above the point where the soldering was done.

Any epoxy is more conductive than air or just N2 so this may also be helping.

Funny, how the only part that was acceptable in our mil spec designs was the metal can variety.

Must have something to do with MTBF.

Whom is laughing at whom now?

Very likely so and its ability to withstand adverse environments most likely because of the hermetic packaging. Irrelevant to anything other than military / aerospace application and the like of course.

I'm laughing at your pathetic attempt to wriggle out of your error by changing the topic.

Graham

Toshiba IME) are

could match

Really ? I didn't know that. I've never used a TIP where speed was an issue.

Graham

"and the like"? You're an idiot. The metal housed device is better for more reasons than the hermetically sealed package, idiot.

It has a much broader range of operation.

I am betting that the epoxy package peters out far sooner in designs where the transistor's capacities are pushed.

You're an idiot. It is still the same topic. It is still a better part.