[time-nuts] Re: hydrogen rich environment and oscillators

[Lux, Jim]

On 12/13/22 9:09 AM, Bob Camp wrote:
> Hi
>
> As price goes down, so must cost. If not, the outfit goes broke. Working
> out just what gets “left out” on a $1 TCXO is almost impossible unless
> you can go do an audit of the production line at the time the parts are
> being made.
>
> Next question would be: Are the parts evacuated before seal? I’d bet not.
> They likely get some sort of inert gas fill and that’s about it. If so, you
> already *have* gas in the package. There’s not a lot that a one gas
> will do vs another as far as damping the crystal. Also, with a more or less
> zero pressure differential, not much He or H is going to work it’s way into
> the package. Yes, this *assumes* the parts are crystal based ….



That's kind of what I thought.  I would think that if it's a MEMS 
device, that the mfr would identify it as such. The Abracon part does 
say "Crystal Oscillator" at the top of the data sheet.


>
> It’s not all that hard to test this out. Get or rig a pressure container that
> will take 50 to 100 PSI. Go over to the local gas store and get a small
> bottle of He or H. Bomb the parts overnight at 50 to 100 PSI. Pull them
> out and see if they still work …… If so, you have just done what is likely
> the “100 year test” on the parts. If they don’t work, see if you have crushed
> the parts ( = smashed the package flat …) and try again at a lower
> pressure … :)

Good idea.

An excellent project for a summer intern.

Of course, at JPL, we'd be much more elaborate, budget permitting - CAT 
scan the package before and after, set up a RGA or Mass Spec, Bring in 
an optical fiber(s)) from the maser to compare the frequency of the 
oscillator. Certify all the high pressure gas handling equipment. The 
test process alone could cost more than buying 100,000 oscillators.

In my garage - the work of a weekend.




>
> Bob
>
>> On Dec 13, 2022, at 10:01 AM, Lux, Jim <jim at luxfamily.com> wrote:
>>
>> On 12/13/22 5:57 AM, Bob Camp wrote:
>>> Hi
>>>
>>> If you have a welded package TCXO, it’s a reasonable guess that it may have gone
>>> through the normal “mil spec” leak test. Mil STD-202 method 112 test condition C
>>> gives you all sorts of fun information. It also heads off in many directions.
>>>
>>> As normally done on a crystal oscillator, you put the parts in a pressure vessel for
>>> about an hour. It’s pressurized at around 50 PSI with 10% helium. Yes both the time
>>> and pressure are past what method 112 calls out as the minimums.
>>>
>>> After being soaked like this, they go into a mass spectrometer to look for helium
>>> coming back out of the parts.
>>>
>>> Pretty much any mil spec or space spec welded part would go through that test or
>>> something very much like it. That’s true regardless of who made the part.
>>>
>>> The only relevant point here is that if this sort of exposure killed the parts, it would
>>> show up and folks would very much know about it.
>>>
>>> Welded crystals going into precision oscillators get the same sort of leak check or
>>> possibly something more in depth. There’s no guarantee on this so it’s not quite as
>>> much a sure thing as the space or mil oscillators. Still, if this killed crystals you would
>>> know about it.
>>>
>>> Before anybody asks, yes, some parts do leak. I don’t remember any of them being
>>> non-functional. However, you don’t test those parts much. They are headed to the
>>> recycle bin.
>>>
>>> Bob
>>
>> OK. so welded packages (particularly those that are procured for space) aren't likely to leak, they tested, etc. I'm sort of interested, though in COTS cheap oscillators like these tiny $1 Abracon units.  (I don't know what they use on Arduinos and RPi, but it's something like this).
>>
>> https://www.mouser.com/datasheet/2/3/ASEseries-38758.pdf
>>
>> They're sort of silent on the datasheet about sealing, etc.  And at $1.38 each, do they actually leak test them?
>>
>>
>>
>>
>>
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