Hi Once you get up to an OCXO sized package, you get quite a bit of volume. On an older TCXO design it’s sort of the same thing. The CSAC falls into a size range that is kind of on the borderline. I have seen packages that size vented in the past.
Bob > On Dec 9, 2018, at 10:39 AM, jimlux <[email protected]> wrote: > > On 12/9/18 7:08 AM, Bob kb8tq wrote: >> Hi >> On a normal OCXO or TCXO design you would put the product in a >> package with a hermetic outer wall to keep out crud and moisture. >> Per the papers cited you would put a small vent hole in a “space grade” >> product. Every time I see an eBay listing with a nutty price on a “space >> OCXO” I wonder if it’s been sitting “vented” on a nice humid / dusty shelf >> for >> decades. > > Actually, you could have hermetic packaging - as long as you show that the > pressure differential won't cause a problem. Tons of ceramic ICs have > hermetic packages (an a variety of XOs, as well). > > It's sort of a judgement/analysis call - if it's something which is a box > with boards, probably easier to vent - if it's something tiny, and people > have been making and flying them for decades, then hermetic. > > We do lots of thick and thin film hybrid circuits which are hermetic - e-beam > welding of the lids and all. > > > > > >> Indeed the only way to test / use product vented like that is to put it in a >> thermal / vacuum chamber (or fly it to outer space). While my basement >> has a reasonable selection of this and that, I don’t seem to have missed >> out on picking up a thermal vac chamber …. >> How different is the performance with air in the package? It turns out to >> be very much a “that depends” sort of thing. Usually not as big a deal >> on a TCXO as on an OCXO. > > for the CSAC, apparently, gas outside the physics package affects the heat > required to keep the gas vaporized in the optical cell. > > _______________________________________________ > time-nuts mailing list -- [email protected] > To unsubscribe, go to > http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com > and follow the instructions there. _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there.
