How to solve the heat cooling problem of high-power LED lighting?
High-power LED lighting belongs to solid-state lighting, which has the advantages of long life, safety and environmental protection, high efficiency and energy saving, and fast response speed. However, there are still some technologies to be solved urgently, mainly including: low light extraction efficiency, high calorific value, and high price. At present, the luminous efficiency of LEDs can only reach 10% ~ 20%, and 80% ~ 90% of energy is converted into heat, which makes the heat flux of high-power LEDs exceed 150 W/cm2, while conventional copper/aluminum heat sinks can only meet The heat dissipation requirement of 50 W/cm2. If the heat cannot be dissipated effectively in time, the junction temperature of the LED chip will increase, resulting in a decrease in the output optical power, leading to chip degradation, leading to wavelength "red shift", and shortening the life of the device. Therefore, how to solve the heat dissipation problem has become the key to the promotion and application of LEDs, and how to observe the heat change is the entry point to deal with the problem.
Considering the small size of the chip and the small size of the circuit leads, a macro lens can be used to observe small-sized objects. On the one hand, the use of infrared thermal imaging cameras and special accessories can detect the inside of the LED chip, and improve the design and quality of LED products by analyzing the internal temperature distribution. The temperature distribution of the gold wire and the positive and negative electrodes can provide R&D personnel with a basis for wiring design. When developing a cooling system for the chip, it is also necessary to confirm the heating of each part of the chip.
Infrared thermal imaging thermal distribution test content of light-emitting diode chip:
1. The temperature value of the entire chip, the maximum temperature of the chip should not exceed 120.
2. The temperature distribution of the gold wire and the positive and negative poles inside the chip.
Note: Due to the small size of the LED chip, the thermal imager needs to shoot at the closest extreme distance, far below the minimum focus distance of visible light, so visible light cannot be displayed in the heat map, or the position of the visible light and infrared heat map is quite different .
On the other hand, the heat dissipation of LED devices is divided into primary package heat dissipation and secondary heat sink heat dissipation. The primary package heat dissipation is mainly through the improvement of the packaging materials and structure of the LED itself, and the secondary heat sink heat dissipation is mainly through the design and development of an external heat sink structure to control the heat dissipation of the LED. The temperature difference between the radiator and the PCB and the heat dissipation efficiency of the heatsink can be observed through the infrared thermal imager.
