Research On The Heat-Release Performance For High Power LEDs Under Fluid Convection

LED is referenced as the fourth generation green lighting with the advantages of low power consumption, environmental protection, small volume, long service life, impact resistance, high reliability, fast response, and so on. With the application of LED in lighting area, LED of high power, high brightness and high quality has become an important development trend. However, the electro-optical conversion efficiency of high power LEDs is still low so far. With the increase of the input power, heat dissipation has become more and more serious for LED device. The peak wavelength of LED will shift, luminous flux and lifetime will be reduced if the junction temperature is very high. So the thermal management of LED is critical to the overall performance. The way to improve the heat dissipation performance of high power LEDs device is one of the key technologies urgently needed to be solved on its development road.In order to achieve high quality and high power LEDs, we must understand the heat dissipation principle and package structure of high power LEDs. For the thermal design of high power LEDs packaging, the most important task is to reduce the junction temperature and thermal resistance effectively. By means of designing a reasonable heat dissipation structure, increase overall heat dissipation. Heat transfer from LED chip to heat sink by heat conduction, then to outside environment by convection. The thermal boundary layer is existed between the solid and fluid, so the way to reduce the thickness of boundary layer is important to increase heat dissipation. So it is beneficial to promoting the advancement of high power LEDs device’s overall performance and reliability, as well as accelerating the process of semiconductor lighting era, to carry on a research on the heat dissipation performance of high power LEDs packaging.The influences on the device’s heat dissipation performance of high power LEDs packaging structures have been researched through the method of combining theoretical analysis and computer simulation analysis in this paper. A novel heat-release structure is proposed under natural convection and the heat dissipation performance of high power LEDs is researched under liquid cooling system. The simulation results show that:(1) The slotted plate can improve the flow feature of fluid field, increase the surface heat transfer coefficient, enhance the capability of heat dissipation. There is a best pitch between two plates to make the junction temperature and thermal resistance lower under the thermal conduction and thermal convection. And the junction temperature and thermal resistance lower 3.2 K and 1.01 K/W respectively when the input power of each chip is 1 W under the best pitch. For slotted plate, the capability of heat dissipation is enhanced obviously with increasing input power for each chip, and it also decreases the weight of plate and reduces the cost.(2) Under the same volume and slotted substrate, there is an optimum number of fins making the performance of heat dissipation enhancing. The junction temperature is lowest when the number of fins is six, and the junction temperature is 345.970 K at the same time.(3) The LED maximum temperature and thermal resistance using the rectangular fin with the inclined angle of 30 degrees is lowest, the heat transfer enhancement is highest, and rhombic fin is followed, vertical parallel fin is worst. The rectangular fin with the inclined angle of 30 degrees and rhombic fin have the higher flow resistance when they have the higher heat transfer performance, because of the oblique angle. Considering the heat transfer performance and flow resistance, rhombic fin has the highest comprehensive performance of heat transfer.The analysis of packaging structure and the heat dissipation principle have great significances to improve the heat dissipation performance of high power LEDs. It has a certain guiding significance for the improvement of high power LEDs packaging to research the heat dissipation performance of high power LEDs packaging, which also provides a new way to solve the heat dissipation problem of high power LEDs.