Conformal coatings are polymer films applied to printed circuit board surfaces to protect them against harmful elements such as moisture, extreme temperatures, and chemicals. These films are thin so that they can conform to the different board shapes and their components. The protective layer they give is critical in ensuring the electronics remain reliable, functional, and durable. https://www.epoxyadhesiveglue.com/what-is-epoxy-conformal-coatings-for-pcb/