High-power light-emitting diodes (LEDs) for lighting applications require a high-efficient packaging to optimize their performances. Due to its high thermal dissipation potential, the chip-on-board (COB) technology is widely used for developing high-power lighting sources. In order to optimize the optical properties of such sources and to propose high optically efficient encapsulation geometry, ray-tracing simulations have been performed. The impact of the shape and volume of the silicone encapsulation on the light extraction and on the intensity distribution of the module was derived. Then, simulation results were correlated with experimental measurements on blue light-emitting COB sources. It is shown that a nearly hemispherical encapsulation with a minimal volume of 5 to 10 mm3 for a 1 mm2 LED die is the optimal configuration regarding both the light extraction and the intensity distribution.