Vacuum-drying of cleaned PCBs?
Well, this becomes a complex question with a very easy answer, if we'll let ourselves be tempted to be so short and uncomplicated:

This varies between suppliers and exact types, and only your manufacturer on a part by part basis can tell you.



However, from experience on small scale (Note that most of what I do in my lab is upto proto-series of 20 pieces, so luck is not highly likely, but also not impossible), I can say many component types fare well under a 70 kPa (0.7 bar) drop of pressure.

Many Electrolytics get specified to vent at hundreds of kPa of pressure differential, if not close to one or two MPa, because the reason for venting is not having it blow up, but small amounts of pressure should not immediately cause destructive failure to the entire device.

Generally the advised threshold for operation, if I am not mistaken, for wet electrolytic capacitors of modern design is 10kPa absolute (in most locations that's -85kPa -or deeper- relative).

The only document I could quickly find is this one stating 3kPa absolute somewhere on page 11. (I'm sure I could find more information from more suppliers if I put the time in).

For Neon lights and the like, these should definitely operate down to pressures like 10kPa absolute, unless their construction is especially shoddy (which is a decent risk these days, possibly even with semi-branded stuff).

But basically anything specified to be used on high-flight-path system in none-pressure-compensated areas should already be vacuum qualified, since your vacuum should build up gradually and usually those parts are specified for pressure-shock and reverse-pressure-shock at low ambient pressure.

This is also a point of attention: The speed at which you build up the vacuum may be even more important than the final pressure, if you let it dip nearly instantly, you may cause a shock allowing something to percussively break from the inside (boil-off or low grade plastic containing micro cavities). But you'd need a very impressive system to be able to do that, I would estimate.

For batteries, well, that is something I'm not going to be touching, as there are a million and one manufacturers, especially lithium types, and not even half of them really consider outside mechanical shocks other than commercial grade testing requirements (if even that!).