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

[Bob Camp]

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

> On Dec 12, 2022, at 5:09 PM, Lux, Jim via time-nuts <time-nuts at lists.febo.com> wrote:
> 
> On 12/12/22 11:21 AM, Zen via time-nuts wrote:
>> This is true and was proven by experimentation. But I believe it was a
>> Helium atmosphere not Hydrogen. The He poisoned the MEMS oscillator in both
>> phones and watches. Fault time was about 30 minutes recovery time was about
>> 3 days. Concentrations were small enough that and employee filling party
>> balloons at a store had a dead I phone for a while.
> 
> Yes, but H2, while a bit bigger than He, is still pretty diffusable (if that's the right word).
> 
> And, I believe the iPhone event was a very tiny MEMS resonator in a vacuum.
> 
> I've been poking through the literature and reports, but it does not appear to be a "well studied problem".
> 
> 
> The challenge is that with Cubesats and the like making more use of COTS components and techniques, there's not a lot of history to go back to.  Space qualified parts get leak tested with He, etc. so their hermeticity is generally good.  The same is not necessarily true of other devices.
> 
> 
> 
> 
> 
>> 
>> Eric
>> 
>> -----Original Message-----
>> From: Poul-Henning Kamp via time-nuts <time-nuts at lists.febo.com>
>> Sent: Monday, December 12, 2022 10:10 AM
>> To: Discussion of precise time and frequency measurement
>> <time-nuts at lists.febo.com>
>> Cc: Poul-Henning Kamp <phk at phk.freebsd.dk>
>> Subject: [time-nuts] Re: hydrogen rich environment and oscillators
>> 
>> --------
>> Lux, Jim via time-nuts writes:
>> 
>>> Does anyone have any information on what happens to hermetic TCXOs
>>> when they're in a hydrogen rich atmosphere?
>> What kind of hydrogen concentration are we talking about ?
>> 
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