First optical design for wide angle micro LED without second lens

Abstract

This study proposed 1st optical design for wide angle micro LED without 2nd lens. Micro LEDs are point light sources that the beam angle of 120°, therefore, a large number of LEDs are needed to achieve a uniform area light source. We used 1st optical design to modulate luminous intensity curve, in which micro LED as chip and through chip scale packaging (CSP) process to design wide angle micro LED that achieve full width at half maximum (FWHM) of 180°. The prototype used a square packaged that with a flip chip. Chip length, width and height of 240um, 130um and 80um respectively, the structure of wide angle micro-LEDs is including flip chip as light source, side wall around chip, a light guide layer, and a diffusion layer. The light guide layer has a great correlation with the light extraction efficiency, the diffusion layer used to control the ratio of the transmittance and reflectivity rate. We analyze the thickness of light guide layer and diffuser layer from 0.1mm to 0.4mm and 0.1mm to 0.3mm, respectively. In which the optimized package structure of thickness of light guide layer of 0.4mm, thickness of diffusion layer of 0.2mm. The prototype shows that light extraction rate of 95%, central light intensity of 25.6%, peak angle at 66° and full width at half maximum (FWHM) of 180°. This design proposed for thin, flexible, and uniform surface light source.