High-power LED typical heat sink structure heat dissipation performance analysis [Figure]

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 [1], so that the heat flux density of high-power LEDs exceeds 150 W/cm2, while conventional copper/aluminum heat-dissipating fins Generally only meet the heat dissipation requirements of 50W/cm2 [2]. 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 et al. [3] proposed a heat pipe radiator for high-power LED cooling combining high-power LED heat dissipation and loop heat pipe heat transfer, and experimented on its heat transfer performance and overall temperature uniformity. the study. Yuan Liulin [4] 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 et al [5] designed an integrated high-power LED that uses semiconductor cooling technology to dissipate heat, which 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 [6] developed a new type of heat sink to achieve the cooling of high-power LEDs. The heat sink is based on natural convection to achieve heat transfer. The cylindrical structure is surrounded by longitudinally distributed fins. To the same sex. SWChau et al. [7] proposed a device for cooling LEDs by electrohydrodynamics (EHD). The ion wind is used to obtain forced convection heat dissipation by gas discharge. The convective heat transfer coefficient is 7 times of natural convection, and the heat sink temperature is Maintain at 20 ~ 30 ° C, and studied the heat dissipation under different conditions. LiuChunkai et al. [8] 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 output. Efficiency, reducing Pn junction temperature, is an effective active cooling method.

Figure 1: Typical secondary heat sink cooling structure

At present, most of the LED street lamp demonstration projects use an all-aluminum heat sink as a secondary heat sink heat dissipation structure. With the development of micro heat pipe technology and the increase of LED device power, micro heat pipe technology has been more and more applied to the secondary heat sink heat dissipation structure of LED devices. In order to study the actual heat dissipation effect of different heat sink structures, this paper designs a high-power LED lighting device with three different heat sink structures, and compares its heat dissipation performance.

1. Performance analysis of typical heat sink structure of high-power LED lighting equipment

1.1 Typical heat sink cooling structure design

Figure 2 shows a high power LED lighting unit (structure I) with an all-aluminum heat sink type heat sink structure. The LED lamp mainly dissipates heat into the air through the thermal conduction of the MCPCB board, the aluminum substrate, the aluminum heat sink rib base, and the heat conduction and natural convection of the aluminum heat sink fin. This structure mainly utilizes a high thermal conductivity metal aluminum alloy as a heat transfer medium, and utilizes aluminum fins as an extended surface to enhance surface heat transfer capability.