Influence of substrate size and gas on thermal and optical performance of LED filament bulbs

Abstract

LED filament lamp with high brightness, low power consumption and long life, is a new generation of LED lighting new light source. Although the high-density integration of LED chips into the substrate can provide more functionality, but the LED filament heat dissipation performance aspects is a major problem affecting the luminous efficiency and reliability. Here, the LED chips were solid-crystallized onto 1.5 mm and 3.0 mm ceramic substrates, and the effects of substrate size and filling gas on the heat dissipation and optical performance of the filament lamps were investigated by finite element analysis (FEA). The heat distribution, luminous flux and luminous efficiency of the bulb surface were analyzed. The simulation results show that filling helium has better heat dissipation and optical performance than filling nitrogen or air, and the average junction temperature of the LED filament decreases from 119.28 °C to 105.40 °C, the luminous flux increases from 551.66 lm to 583.38 lm, and the luminous efficacy increases from 142.5 lm/W to 151.1 lm/W when the substrate size is changed from 1.5 mm to 3.0 mm. It can be seen that increasing the size of the substrate, LED filament lamp heat dissipation effect and optical performance is better. Experimental tests also support the simulation results. The results provide guidance for the thermal design of high-power LED filament bulbs.