The environmental condition is generally the same as for other electronic equipment. When operating outdoor and in high humidity environment, two commonly used techniques can be used to extend the lifetime of the product:
1. Encapsulating (Potting) the board with epoxy or silicone
2. Conformal coating techniques as spraying, wiping, dipping, or painting the board with silicone, acrylic, urethane, epoxy etc
Several external sources informs us that the RF performance stays the same. Some of the conformal coating resin containing Urethane that may interfere with RF signals, and should be ruled out as coating resin type for your application. The ideal coating should exhibit high resistivity and dielectric strength to ensure electrical integrity. These characteristics should not deteriorate with changes in temperature and humidity. Equally, the electrical properties should not affect circuit performance. For example, some coatings work well at low frequencies but can cause circuit malfunctions at higher frequencies. The dielectric constant and Dissipation Factor begins to increase, while resistance and dielectric strength decrease. Q-factors of coils generally lessen with increasing frequency and coating thickness. Hopefully the assembly house can help you out more based on this general info.
Last Update: October 23, 2017