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

[Bob Camp]

Hi

Depends a lot on what you call a “hermetic TCXO”. 

There are a lot of parts out there that have sealed crystals inside a sealed TCXO package. 
The TCXO package might be resistance welded, it could be solder sealed, it might be glued
shut. The crystal likely is resistance welded or cold welded in a separate enclosure inside
the TCXO package. The TCXO package likely has an inert gas in it at around 1 atmosphere. 

There are other parts that have an open blank inside a single package. The package probably 
is welded shut, but these days … who can be 100% sure of anything :) 

On top of this, a sealed crystal might be in a vacuum or it could be in some sort of inert gas ( often 
at pretty low pressure). The same is true of OCXO crystals. The single package unit could
be evacuated or backfilled, possibly at a fairly high ( = close to an atmosphere) sort of pressure. 

So lots of variables. 

Worst case is a vacuum packaged high Q crystal. It gets gas instead of vacuum and the Q 
goes down. If it goes down enough, the oscillator quits. Not a really high probability in a TCXO.
There are parts out there though.  If the crystal is inside it’s package *and* that’s inside a second
hermetic package, it’s going to take a long time for your hydrogen to get to the crystal ….

Bob

> On Dec 8, 2022, at 4:28 PM, Lux, Jim via time-nuts <time-nuts at lists.febo.com> wrote:
> 
>    OK, here's an interesting one for you all:
> 
> Does anyone have any information on what happens to hermetic TCXOs when they're in a hydrogen rich atmosphere? There's stories about MRI machine He rich environments killing Apple watches - I think, though, that was a MEMS oscillator. The data shows a reduction in Q because the resonator's not in a vacuum.  And I'm aware of pressure sensors failing because they rely on a vacuum for comparison. But I wouldn't necessarily think this is the case with a quartz crystal.  Or is it?  H2 is somewhat more reactive than He, too.
> _______________________________________________
> time-nuts mailing list -- time-nuts at lists.febo.com
> To unsubscribe send an email to time-nuts-leave at lists.febo.com