Hi Everyone, I’m working on a board that will be used for low frequency measurements in a cryogenic environment. I’m currently planning on using a polyimide substrate, ENIG surface finish, and terminating components with PbSn solder. None of the circuitry on the board will generate significant heat but the ramp from room temperature to cryo temperatures and back will be fairly rapid.
Any issues with these materials or other recommendations for improving board reliability?
Thanks!
That’s a good starting point in terms of materials! It is worth mentioning that the NASA standard for temperature swing is only about 3-4degreesC per minute. Depending on what you mean by rapid ramp, you may be getting into the territory of thermal shock regularly, which is likely more damaging to any given off the shelf part than the actual cryogenic temperature itself.
I agree. I’ve done some low temp stuff before but nothing with a rapid ramp. The good news is I don’t expect a lot of cycles.
I figure the same principals apply but I’m always pleasantly surprised by the range of knowledge of this community.
Nasa’s standard is not international and the only one… For tests in challenging climates, you need to… 1 apply suitable components (usually they are more expensive and have a wider range) 2 provide board protection with a suitable compound (there are many different with different properties) 3 make a complete statement of work for the project… Taking a piece of the project and trying to fit it is no longer the right solution
Sure, I’m not claiming NASA controls the One And Only standard for this kind of thing, it just happens to be the standard I use regularly and mostly trust to be based on experimental data that has been proven in production. In this case it is a good rule of thumb to differentiate “normal” mechanical properties from the name mechanical properties when undergoing thermal shock.
I agree that in this case a conformal coat like Arathane (other products are available) after assembly and test would probably help, especially if the environment isn’t guaranteed to be dry (I know keeping dry nitrogen dry when the nitrogen itself is threatening to condense is… difficult).
Depending on the circumstances, this might range from tricky to do with off the shelf parts to impossible, but I’m curious to know more/how it goes if it can be made public!
edit: I typed “over the counter”, definitely meant “off the shelf”. Too much time spent dealing with insurance this week
If I were looking for Information re PCB/etc and Cryogenic’s, I’d contact resources at CERN as they are at the top of the list… And, they use/support Kicad Click This Link
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