Study on the influencing factors of thermal spreading resistance of HP-LED package

The optical performance and reliability of High power light emitting diode (HP-LED) devices can be affected by the junction temperature, while thermal resistance is one of the main factors which influence the p-n junction temperature, especially for the thermal spreading resistance. So, Thermal analysis was conducted by differential structure functions combining with finite element analysis and calculation of thermal spreading resistance of HP-LED devices. The results show that thermal spreading resistance plays an important role on total thermal resistance of LED devices. The thermal spreading resistance shows a declined and then increased trend with the increase of substrate thickness; the contact area between the heating source and substrate is the main factor which influences thermal spreading resistance; It is beneficial to decrease the thermal spreading resistance when contact area ratio be increased. Thermal-convection resistance becomes the main factor that influences total thermal resistance of HP-LED devices with the changing of substrate bottom area, while the influence of thermal spreading resistance is weak. The eccentric distance between chip and substrate plays a distinct impact on thermal spreading resistance and junction temperature. The results of finite element simulation are in good agreement with calculation of thermal spreading resistance.