Humidity stopping LF oscillator on nRF52840

[jabus1]

I am using the Fanstel BT840 module with an Epson FC-135 32.7680KA-AC3 crystal and 12pF NPO caps. It functions well in indoor conditions but the LF oscillator stops if placed in humid conditions. The layout traces are as short/direct as possible. Conformally coating the oscillator and module cure the problem...but I'm wondering if what I'm seeing is to be expected? 3 or 4 breaths on the un-coated module/oscillator will shut it down. Is it standard practice to have to conformally coat the nRF52840 for reliable operation in humid environments? Is the Internal LF oscillator option a better choice for  humid environments? Thanks.

[Kaja]

Hi Jason,

I haven't heard of a similar situation before. But the load capacitance of the crystal you are using is 9 pF, could you try to change the NPO caps to 15pF(optimal 14pF), and see if the same happens? 

And could you try to do the same as you have done, but with our DK?

Best regards,
Kaja