This question may seem awkward: what's inside a TO3 or similar metal-can puck? Do they contain air?
I am asking because colleagues at work are looking for old / archived air that could be analyzed for trace gases in order to reconstruct the trace-gas evolution of the atmosphere / air during the past few decades. Any insights or thoughts would be welcome.
I am asking because colleagues at work are looking for old / archived air that could be analyzed for trace gases in order to reconstruct the trace-gas evolution of the atmosphere / air during the past few decades. Any insights or thoughts would be welcome.
Have no idea, but would not be surprised they are closed in an inert environment, argon for example??
next question would be whether the enclosure is gas-tight over decades to allow atmosphere analysis?
... what about air in water proof (swiss) watches? ok, a bit more expensive ;-)
... what about air in water proof (swiss) watches? ok, a bit more expensive ;-)
REAL TO-3’s are hermetic so they stay gas tight for decades. This cuts both ways - anything that outgasses remains trapped. It’s just air inside them, but it is dry (as in no or very low water content so nothing condenses at -40C).
Fake TO-3’s are nowhere close to hermetic, and moisture ingress will eventually kill them even if they are used within their capabilites. That’s why they use the silicone - in a vain attempt to keep them working for longer.
Fake TO-3’s are nowhere close to hermetic, and moisture ingress will eventually kill them even if they are used within their capabilites. That’s why they use the silicone - in a vain attempt to keep them working for longer.
I'd suspect dry nitrogen or argon are possible atmospheres used to prevent oxidation or condensation. Even if the packaging was done in ordinary air it would be in an industrial environment, so you'd expect contaminants like solvents to be present that aren't representative of the normal atmosphere.
Many trace gasses are possibly going to react with metals (other than gold perhaps), a glass enclosure is a more stable environment than metal for chemical changes (other than for light-catalyzed reactions). Sealing glass enclosures though is done with a flame, again contamination from the fuel gasses might be expected.
I think its very unlikely an accidental archive of atmosphere exists that hasn't issues limiting its reliability. But there might be several that can be cross-checked.
Many trace gasses are possibly going to react with metals (other than gold perhaps), a glass enclosure is a more stable environment than metal for chemical changes (other than for light-catalyzed reactions). Sealing glass enclosures though is done with a flame, again contamination from the fuel gasses might be expected.
I think its very unlikely an accidental archive of atmosphere exists that hasn't issues limiting its reliability. But there might be several that can be cross-checked.
It is interesting concept.
Seems like the air samples would only represent transistor factory atmosphere conditions.
I'm only guessing done also with high vacuum. So not sure if sample would be instantly contaminated,
if seal broke open , or if transistor contains nothing useful because of vacuum
having watched a lot of " revival " videos lately of old cars.
They do get lucky and cars that have been sitting for 30 or 40 years still have air in some tires.
Assume positive compressed air has more samples than, negative vacuum.
Year of car obviously doesn't tell you sample date. Sample date is when car was parked
and how long been abandoned.
If vacuum sealed devices have actual valuable data. Then likely sealed beam headlights
or lightbulbs could be used.
Seems like the air samples would only represent transistor factory atmosphere conditions.
I'm only guessing done also with high vacuum. So not sure if sample would be instantly contaminated,
if seal broke open , or if transistor contains nothing useful because of vacuum
having watched a lot of " revival " videos lately of old cars.
They do get lucky and cars that have been sitting for 30 or 40 years still have air in some tires.
Assume positive compressed air has more samples than, negative vacuum.
Year of car obviously doesn't tell you sample date. Sample date is when car was parked
and how long been abandoned.
If vacuum sealed devices have actual valuable data. Then likely sealed beam headlights
or lightbulbs could be used.
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Car tires are no good.
They smell of rubber if you let air out of them. You certainly do not need a lab to establish what the air has been contaminated with.
They smell of rubber if you let air out of them. You certainly do not need a lab to establish what the air has been contaminated with.
I was just reading that rubber allows permeation of nitrogen, oxygen and other gasses both ways per the laws of partial pressure of gasses, so tires would NOT be a good source of "old" air.
Real TO-3 transistors are hermetically sealed, so what ever "air" is in them should be as good as 'new', except for possible out-gassing of the internal components (i.e. silicon, aluminum, adhesives, etc.). As to what the "air" is? - my guess would be dry nitrogen. You would not want to risk contamination from unknown elements in plain air. It is also possible that an inert gas (i.e. argon) could be used, but nitrogen is so much less expensive.
Real TO-3 transistors are hermetically sealed, so what ever "air" is in them should be as good as 'new', except for possible out-gassing of the internal components (i.e. silicon, aluminum, adhesives, etc.). As to what the "air" is? - my guess would be dry nitrogen. You would not want to risk contamination from unknown elements in plain air. It is also possible that an inert gas (i.e. argon) could be used, but nitrogen is so much less expensive.
Thats bad idea. Even if there is an air inside from the time it was assembled, it would nor represent planet atmosphere. It likely was filled in factory full of all sorts of solvents used, normal for electronic industry.
Semiconductors are manufactured under very very very very clean conditions, that´s where the "clean room" idea comes from, so it is NOT a reference for Earth´s atmosphere conditions.
Just how much air from the relatively brief modern period (only a few decades) might you expect to recover from an ice core? If you wanted to track the atmospheric changes of modern times, you'd probably need litres of the stuff to play with (density about 1.25 kg/cubic metre at STP) and many traceable sample locations. You'd likely also need accurate histories for the samples and/or their containers.
Otherwise, I think the gas inside transistor cases is going to vary from one example/process/fabrication plant to another and from one lot or storage location to another. Without large numbers of samples, the net result of testing the trapped gas would be unlikely to demonstrate or prove anything related to the local environment but it could give curious minds something to think about. Obscure thesis topics, maybe?
Otherwise, I think the gas inside transistor cases is going to vary from one example/process/fabrication plant to another and from one lot or storage location to another. Without large numbers of samples, the net result of testing the trapped gas would be unlikely to demonstrate or prove anything related to the local environment but it could give curious minds something to think about. Obscure thesis topics, maybe?
No, ice cores are tricky when it comes to reconstruction of the past few decades or so. The trapping mechanisms are complicated, and the gases will diffuse through the ice. Both will smear the archive and make it hard to put a date on the record.
I depends on which gas species you're interested in. If you're looking at something that is involved in the manufacturing process, then that will be a problem. I am well aware of these issues. I simply wondered if it's actually worth thinking about throwing a TO3 at one of our gas machines, or if it's a waste of time.