PCB layout optimization for LED backlight module using FEM simulation

Abstract

Nowadays the size of Liquid Crystal Displays (LCD) displays on the market has a continuous ascending trend which demands higher and higher resolutions. The backlight system of a LCD is the structure that offers light which passes through the liquid crystals layer. No matter what method is used, it has to provide a high luminous intensity and a uniform light distribution on screen visible surface. One significant problem in such designs is the difference in light intensity of individual LEDs due to their different junction temperatures. This paper presents a method of optimization for a LED matrix assembly, where the main purpose is to improve the thermal uniformity on the PCB in order to reduce the luminous flux output difference between the devices, while also maintaining the junction temperatures in the acceptable operating range. As a consequence, the need of custom pattern diffusers used in the LCD displays as light uniformity corrections structures can be eliminated. The method implies defining the geometry for the cooling areas on the PCB by using a specific formula obtained after curve fitting FEM simulation results.