Encapsulant

An encapsulant in electronics and optoelectronics is a polymer resin, gel, or composite material used to seal and protect a component, assembly, or device. The primary functions are environmental protection against moisture, dust, chemicals; mechanical support; electrical insulation; and, in some cases, optical coupling or thermal management. Encapsulants are selected for properties such as transparency, dielectric strength, adhesion to substrate, and resistance to UV, temperature, and humidity. They are cured by heat, moisture, or light, depending on formulation.

Common materials include ethylene-vinyl acetate (EVA), widely used in photovoltaic modules as an encapsulant to laminate cells to glass and backsheet; it provides adhesion and moisture barrier but can yellow and degrade under UV and heat. Silicone elastomers are used for encapsulating LEDs, sensors, and automotive electronics where high temperature resistance and optical clarity are required; silicones offer excellent moisture resistance and elasticity but can be more expensive. Epoxy resins and polyurethane encapsulants are used for potting and protection of electronics and fiber optics; epoxies offer strong adhesion and chemical resistance but can be brittle. Polyolefin and other thermoplastic encapsulants are used in some applications for flexibility and lamination compatibility.

Applications span solar modules, microelectronics packaging, LED optics, medical devices, and consumer electronics. Encapsulation must balance process compatibility with device geometry, optical requirements (in PV LEDs), and reliability under thermal cycling and humidity. Failures can include delamination at interfaces, cracking from stress, yellowing from UV exposure, and moisture ingress leading to corrosion.