When I worked in the defense industry, all of the equipment we designed was built to handle -40C to +90C. Conformal coating was done on every board that went into the devices. Even though our standard was -40C to +90C, we tested them to -63C to +125C. Conformal coating made that possible, plus it helped the devices meet salt corrosion tests.
--Hank
KB4MTO / TA5ZC
