I have an IoT device that consists of a PCB that goes inside a watertight enclosure. The device will operate under constant water, since it will be installed below sprinklers. For an added layer of protection, mainly due to possible human errors when closing the case, I want to add a silicone conformal coating to protect against moisture or small amounts of water that may leak inside. However, my PCB uses a Microchip RN2903 LoRa module, which has an RF metallic shielding as shown below:
As you can see, the module has three small holes on the top, as well as vertical gaps in each corner. My main question is: If I completely cover the holes in the metal shield, could the trapped air inside the shield then cause problems to the module? Maybe due to the pressure of temperature change? The inside temperature of the device is about 15 Celsius at night and 40 Celsius in the day. Then again, the whole inside of the device would have these temperature changes, not just the RF module, so maybe it would be fine?
If you have any ideas, or suggestions on conformal coating modules with an RF shield, please let me know!