Re: PCB's in liquid nitrogen

TheQuickBrownFox <thequickbrownfox@xxxxxxxxxxxxxxxxxx> wrote:
: That's why the right way is with an environmental chamber.

I mostly do LHe work and there I just leave the circuit to the
top of the dewar neck and let it warm up before opening the neck flange.
The circuit gets flushed by evaporated, warmed-up dry helium.

With LN (there is typically no flanged neck in LN dewars) you can
just quickly slip the circuit into a plastic bag and let it warm up
there. Some people like to evacuate the bag or fill it with dry
nitrogen, but IMO it is enough to just squeeze out most of the air.
The circuit catches a small amount of moisture anyway when moved from
dewar to the bag, but most of the frost (when kept in open air) comes
from the unrestricted airflow that goes by the circuit and deposits
its moisture on the cold surface.

Regards,
Mikko
.

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