Re: PCB's in liquid nitrogen

On Fri, 29 May 2009 08:42:16 -0700 (PDT), ggherold@xxxxxxxxx wrote:

Does anyone have experience using printed circuit boards at liquid
nitrogen temperatures? The best I could find on the web was liquid
nitrogen used for stress testing PCB's.

Certain components fail to operate well above that temp. That is likely
why you will NOT find ANY info on any such test routines.

I would suggest a perfluorocarbon fluid like "fluorinert" from Dupont.

Also, there are likely many commercial refrigerants that would be more
suitable.

What the industry typically does is use an environmental chamber at
zero humidity which will go down to a couple hundred degrees F below
zero. If you really need immersion, the fluorinert or a refrigerant that
will not evaporate too quickly would work. The fluorinert is a
dielectric fluid, meant for such purposes.


The boards will be single sided and have either wires or through hole
components attached, resistors and diodes (nothing active). At the
moment I'm most concerned with having the copper traces peel up from
the substrate.

Then hard wire everything, and encapsulate

Would heavier copper help? (2 oz. or 4 oz.) I would
hope to use a standard substrate material FR-4, G10....

If the component count is low, as a single sided solution suggests, you
could simply skip the PCB and point to point wire it, and pot the
finished assembly into a monolithic block or ball.

Anyway... what you seek is environmental chambers. Not likely wise to
play with a PCB and raw LN.
.