An Efficient Process of Surface Modification and Patterning for LED Encapsulation

Encapsulation is a critical step in LED packaging to ensure good light extraction and protection. We present a novel mold-free process using a specific functionalization of the substrate to master the shape of the encapsulant dome. By controlling its aspect ratio, it is possible to increase light extraction. Experiments are correlated with Monte Carlo simulations to evidence the impact of surface tension on the dome shape as well as the effect of the refractive index on the light output. A moderate optical gain of 10% is obtained as the refractive index of the encapsulant material increases from 1.42 to 1.64, which is explained with the simulations as a strong effect of the die parameters (roughness and back mirror) on the light extraction.