Study And Optimization Of Heat Dissipation Of GaN Based High Power LED Chip

Light emitting diode(LED) is made of compound semiconductor light emitting components, through electron-hole combined to convert electrical energy into light. Energy conservation demand for high-performance solid-state lighting has led to a sharp escalation in LED industries, increasing the power density and the current level in LED chips has been used to reduce cost. However, there are side effects in the LED due to self-heating. One challenge in developing LEDs is their thermal behavior, because higher temperatures will reduce the lifetime and the light output of the devices. For good thermal management of high power LED is the basis of its widespread application. In this paper, we have studing and optimizing the GaN based high power LED three dimensional thermal model, which is established by using the COMSOL Multiphysics finite element software.Firstly, the basic structure and working principle of GaN LED was introduced and the reason for heat generate. A series of effects on the performance of LED and Current status of thermal management wsa described. Set forth the principle of steady-state heat conduction and thermal resistance calculation of chip modules, introduces the concept of contact thermal resistance and proliferation resistance. Based on this, high-power LED package thermal resistance of one-dimensional model is established.Secondly, in this paper, the influence of grain binder on the heat dissipation of high power LED is analyzed in detail by the three-dimensional thermal model of high power LED, and the effect of the phosphor temperature on the LED junction temperature is also analyzed. The results show that both the junction temperature and the junction-to-board thermal resistance are greatly affected by the thermal conductivity of die attach adhesive materials, the die attach adhesive bonding area and the bond-line thickness. A better crystal layer design example is the thermal conductivity of die attach adhesive materials is 20 W/mK, the bonding thickness is 20 μm, and the area is 1 mm2. The junction temperature is 337 K at a given ambient temperature. The simulation analysis of the phosphor layer showed that the temperature of YAG phosphor was slightly increased when the concentration of YAG phosphor was increased on the basis of 70 wt.%. In general, increase the heat radiating fins, causing the junction temperature to reduce 18 K, when the fin height is less than 20 mm, with the fin height increase, the junction temperature decrease is significant; when the fin height greater than 20 mm, continue to increasing the fin height on heat transfer has little effect.Finally, in this paper, the heat dissipation of high power LED is optimized from two aspects. On the one hand, using the variable cross section fin, the junction temperature is reduced by 22 K. On the other hand, a new integrated heat dissipation structure is proposed, which uses diamond and metal as an integrated thermal diffusion layer. The simulation results show that the junction temperature of LED is decreased by 11 K and 4.9 K, respectively, under the condition that the diamond and metal thickness is 4 μm and the dissipation power is 0.8 W.