Mold-Free in Situ Formation of Encapsulating Lens With Controllable Viewing Angle for LEDs by Photosensitive Polymerization Process

Using photosensitive epoxy resin liquids as encapsulation materials, a mold-free encapsulation technology is developed in this paper to form lenses on light emitting diode (LED) chips with controllable viewing angles. The light emitted by the LED itself is used to trigger polymerization of photosensitive resins. The shapes of the encapsulation lens are controlled by the “nucleus” formed in the initial stage and by the surface tension of the photosensitive resin liquid. LED packages with viewing angles of 90° and 165° are fabricated in this paper as examples. Encapsulations with other viewing angles are expected to be achievable when using liquids of corresponding surface tension. The whole packaging process can be completed within 20 min, or even less, at room temperature and normal pressure.