What metal/plating is the TO18 2N2222 made of?

Thread Starter

AlbertHall

Joined Jun 4, 2014
10,558
Does anyone knwo what metal and what plating is used for the TO18 version of the 2N2222?
All I have managed to discover is that it is 'metal'.
 

ZCochran98

Joined Jul 24, 2018
96
If not nickel plated steel (I, too, don't have a 2n2222 or magnet on hand to check), it could also be aluminum. I suspect that one is the most likely case, considering they're designed to work for heat dissipation, specifically with aluminum heat sinks, and nickel plated steel (or other ferric materials) don't have the best thermal properties (in that they heat up much more quickly than aluminum does with the same amount of power dissipation).
 

Reloadron

Joined Jan 15, 2015
5,667
If not nickel plated steel (I, too, don't have a 2n2222 or magnet on hand to check), it could also be aluminum. I suspect that one is the most likely case, considering they're designed to work for heat dissipation, specifically with aluminum heat sinks, and nickel plated steel (or other ferric materials) don't have the best thermal properties (in that they heat up much more quickly than aluminum does with the same amount of power dissipation).
That's a good point.

Ron
 

Thread Starter

AlbertHall

Joined Jun 4, 2014
10,558
Don't have one handy here to take a magnet to.
I have one (several actually), and a magnet, and both the case and the leads are magnetic.

[moments later] Thanks @dl324.
That means some thought will be needed as I plan(ned) on having one of these to detect water flow (by the water cooling the transistor) but now I will need to consider whether the case will rust away :oops:
 

ZCochran98

Joined Jul 24, 2018
96
Here's info from Central Semiconductor Corp. Can is mostly iron, external coating is tin.
Huh. I couldn't find this for the life of me. Turns out I was mostly wrong about my guess (though there is some aluminum, just not significant-enough amount to consider my answer remotely correct.)

And @AlbertHall: the outer layer of the can plating is tin, so you probably (?) won't have to worry about rusting. That, combined with the inner layer of nickel (which is a frequently-used sacrifice metal, I might add) for the plating and the alloy makeup of the actual can itself (iron-carbon-manganese-aluminum), you may not have to worry about rusting (but that's only a semi-educated guess!)

Out of curiosity, based on what you said, were you planning to use these transistors as water (or water flow) sensors? Or did I misunderstand your intentions?
 

Alec_t

Joined Sep 17, 2013
11,744
A layer of water-proof varnish etc on the case would prolong its life, albeit at the expense of reducing somewhat the sensitivity to water flow.
 

Thread Starter

AlbertHall

Joined Jun 4, 2014
10,558
A layer of water-proof varnish etc on the case would prolong its life, albeit at the expense of reducing somewhat the sensitivity to water flow.
Yes, I think I will do that. After it is secured with silicon rubber into the pipe it won't be too easy to replace.
 

andrewmm

Joined Feb 25, 2011
658
Its an interesting idea,
my friends sail boat has a wind speed / direction indicator based on a heated transistor system,
but

I'm thinking about my computer water cooling system.

a wet liquid, as opposed air, is likely to be same temperature with flowing and none flowing liquid unless a LOT of heat is used. Water needs a lot more energy to heat up than air.
 

Thread Starter

AlbertHall

Joined Jun 4, 2014
10,558
You could try a PN2222 - epoxy doesn't rust, at least the last time I checked (!).
But the thermal conductivity will be lower and it will be harder to seal into a pipe. The metal version is circular and has a flange which will make fitting it much easier.
 

jeffl_2

Joined Sep 17, 2013
28
"Pipe"? I hope you're thinking in terms of plastic, because the difference in thermal conductivity between an empty copper pipe and one full of water may not be as great as you think.
 
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