Thank you all.
sorry for the delay responding, I had to deal with all my "Happy Birthday"
wishes on LinkedIn
(just kidding)

Anyway, I was referring to the FR4 board material itself. IPC-4104/126 in
particular
I knew it couldn't be a problem, but I kind of had a brain freeze when
someone asked me about it.
Then I couldn't find any reference to it in the literature I have...

Sometimes I can make a guess just because of the fact that if it really WAS
a problem,
I probably would have heard about it sometime in the last 30 years,
but my colleagues would rather have a published source than my speculations
(smile)

thanks to everyone,
Jack

On Thu, Jun 2, 2016 at 12:39 AM, John Burke <[log in to unmask]> wrote:

> As Doug would say "it depends" are you referring to the PCB or the PCBA?
>
> If it's the PCBA, If it's switched on and taken down to -40 there should
> not be too much of a problem. Switching on power to a cold board at -40
> depends on the circuit. Some components are only rated to -10 and will not
> fire up from colder temps.
>
> If the circuit is capable of powering up from -40 be sure to use
> automotive grade components as some overmold and other materials used in
> chips have very different properties at low temperatures and this can be a
> problem when a circuit powers up from -40 and the silicon hits +80 degrees
> when encapsulated in a low thermal transfer coefficient material whose
> properties have changed due to the low temp. If you research that is why
> automotive components tend to use different molding compounds.
>
> *Best regards,*
>
>
> *John Burke*
>
>
>
> On Jun 1, 2016, at 10:35 AM, Jack Olson <[log in to unmask]
> <[log in to unmask]>> wrote:
>
> Has anyone ever heard anything about the reliability of circuit boards in
> cold environments?
> (continuous -40C)
> I couldn't find anything on TechNet or in the Printed Circuits Handbook...
>
> thanks,
> Jack
>
>
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