Expert analysis: heat dissipation performance analysis of high-power LED typical heat sink structure (with photos)

High-power LED lighting is solid-state lighting, which has the advantages of long life, safety and environmental protection, high efficiency and energy saving, fast response, etc. However, there are still some technologies that need to be solved urgently, mainly: low light extraction efficiency, large heat generation and high price. At present, the luminous efficiency of LEDs can only reach 10% to 20%, and 80% to 90% of energy is converted into heat, so that the heat flux density of high-power LEDs exceeds 150W/cm2, while conventional copper/aluminum heat-dissipating fins can only generally Meet the 50W/cm2 heat dissipation requirements. If the heat can not be dissipated in a timely and effective manner, the junction temperature of the LED chip will increase, resulting in reduced output power, chip degeneration, wavelength "red shift", and shortened device life. Therefore, how to solve the heat dissipation problem becomes the key to the promotion and application of LED.

The heat dissipation of the LED device is divided into two parts: one package heat dissipation and the second heat sink heat dissipation. The heat dissipation of the primary package is mainly to improve the heat dissipation of the LED package material and structure. The heat dissipation of the secondary heat sink is mainly through designing and developing the external heat sink structure. The LED is thermally controlled. Therefore, in order to truly achieve effective heat dissipation of high-power LEDs, it is necessary to solve the problem of primary heat dissipation and secondary heat dissipation at the same time. A common secondary heat sink heat dissipation structure is to place a plurality of high-power LED arrays on an aluminum heat sink, as shown in FIG. With the increase of the application LED power, a new secondary heat sink heat dissipation structure such as heat pipe heat dissipation, liquid cooling heat dissipation, and thermoelectric refrigeration heat dissipation has appeared. Lu Xiangyou proposed a heat pipe radiator for high-power LED cooling combining high-power LED heat dissipation and loop heat pipe heat transfer, and experimentally studied its heat transfer performance and overall temperature uniformity. Yuan Liulin designed the microchannel cooling structure of high-power LED array package, and used thermal analysis software to simulate the thermal performance and its parameters. Tang Zhengwei and others designed an integrated high-power LED that uses semiconductor cooling technology to dissipate heat. It not only has good heat dissipation effect, but also enables LED devices to work normally in harsh environments such as high temperature and vibration. PetroSki has developed a new type of heat sink to achieve high-power LED cooling. The heat sink is based on natural convection to achieve heat transfer. The cylindrical structure is surrounded by longitudinally distributed fins. This design can achieve heat dissipation isotropic. SWChau et al. proposed a device for cooling LEDs by electrohydrodynamics (EHD). The ion wind is used to generate forced convection heat by gas discharge. The convective heat transfer coefficient is 7 times of natural convection, and the heat sink temperature is kept at 20. ~30 ° C, and studied the heat dissipation effect under different conditions. LiuChunkai et al. integrated silicon-based thermoelectric coolers (te) with flip-chip high-power LEDs, studied the performance of high-power LEDs, and confirmed that the thermal resistance of silicon-based thermoelectric coolers can be reduced to zero, and can effectively improve the light-emitting efficiency and reduce Pn junction temperature is an effective active cooling method.

Figure 1: Typical secondary heat sink cooling structure