High power LED assemblies for solid state lighting – Thermal analysis

We report on the Chip-on-Plate (COP) packaged high power LED assemblies for solid state lighting (SSL) and backlighting display applications from thermal analysis perspective. Three different light modules with different elements (devices) distribution and heatsink design were considered. Thermal resistance circuit (TRC) model and heat diffusion equation were employed in this study of thermal behavior of the assembly elements. Finite element analysis along with 3D modeling and simulations were used for considered lighting modules and assemblies. Also, the effect of thermal uniformity on the emission spectra was evaluated for different operating powers. Comparative study showed that conventional packages with circularly symmetric having non-uniform devices’ distribution per unit area will have temperature differences ∼7 °C among the chip-elements operating around 1.25 W power level. Also, it was predicted that high elements temperature difference could result in over 2 nm redshift in the emission spectra accompanied by ∼ 4% drop in the output power. However, temperature difference was found to be less than 1 °C for the uniform rectangular array module distribution, which ensures uniform output intensity for all devices. Such findings are extremely useful for designing larger area LED packaging where thermal non-uniformity effects are expected to be more severe for devices’ longevity and performance.