PCB - Surface Treatments

I was interested to see how important surface treatment was when PCB's are exposed to the elements.

My approach is take a LED flasher circuit board which can be left undisturbed for months, apply a treatment, and leave it exposed to the elements. 

Initial exposure to the elements was mid-day on 22/11/2022. That night a fierce electrical storm hit and gave everything a good drenching. Several such weather events took place over the test period.

    Date            Status

    22/11/22    5 Boards with different treatment and one board without treatment.

                       Placed outside in the open, surface mount component side facing upwards. 

    20/12/22    All 6 boards still functioning 

    23/2/23       Results after 3 months of harsh summer weather and several very wet rainfall events
                       as follows:

 

 

The test fixture after 3 months.

Conclusion:

Not a definitive test by any means. However, it appears any kind of treatment you have to hand is going to be better than no treatment when a PCB is exposed to the elements.

For low cost battery operated sensors housed in any kind of container I'd probably not bother. The life of such devices is several years at best, not decades, and by the time the battery needs replacing I suspect the device will be technologically obsolete.

Do you have any experience you'd like to share? I look forward to hearing your comments below.

73's