Four key factors affecting the light transmission efficiency

Date:2021-04-06Author:leduntech

/n/n1. Heat dissipation/nAs the temperature increases due to heat loss, the light-emitting diode brightness will no longer continue to increase proportionally to the current, indicating thermal saturation. In addition, with the increase of junction temperature, the peak wavelength of luminescence will shift to the long-wavelength direction, about 0.2-0.3 nm/°C, it will lead to the mismatch of excitation wavelength with phosphor, which will decrease the luminous efficiency of white LED and change the color temperature of white LED./n/nFor packaging and application, how to reduce the thermal resistance of the product so that the heat produced by the PN junction can be distributed as soon as possible, not only can improve the saturation current of the product, improve the luminous efficiency of the product, at the same time, it also improves the reliability and life of the product. In order to reduce the thermal resistance of products, first of all, the choice of packaging materials is particularly important, including heat sink, adhesive, and so on, the thermal resistance of materials to be low, that is, good thermal conductivity. Secondly, the structure design should be reasonable, the thermal conductivity of each material should match continuously, and the thermal conductivity between the materials should be well connected to avoid the heat dissipation bottleneck in the heat conduction channel and ensure the heat dissipation from the inner layer to the outer layer. At the same time, from the process to ensure that the heat in accordance with the pre-designed heat dissipation channel in a timely manner./n/n/n/n2. Choice of filler/nAccording to the law of refraction, when the incident angle reaches a certain value, that is greater than or equal to the critical angle, full emission will occur. In the case of Gan Blue Chips, the refractive index of the Gan material is 2.3. According to the law of refraction, the critical angle θ0 = Sin-1(n 2/n 1) , when light rays radiate from the inside of the crystal to air/n/n/n/nWhere n 2 equals 1, the refractive index of the air, N 1 is the refractive index of Gan, and the critical angle θ0 is calculated to be about 25.8 degrees. In this case, only the incident angle ≤25.8 degrees can be emitted. It is reported that the external quantum efficiency of GAN chip is about 30%-40% , the proportion of light that can shoot out of the crystal is very small. It is reported that the external quantum efficiency of GAN chip is about 30%-40% . Similarly, the light from the chip to pass through the packaging material, transmission to space, but also to consider the impact of materials on the efficiency of light. Therefore, in order to improve the efficiency of LED packaging, it is necessary to increase the value of N2, that is, to increase the refractive index of packaging materials, to increase the critical angle of products, so as to improve the efficiency of LED packaging. At the same time, the packaging material for light absorption to be small. In order to improve the proportion of light, the package shape is best arched or hemispherical, so that the light from the package material into the air, almost vertical to the interface, so no longer have total reflection./n/n/n/n3. Phosphor selection and coating/nFor white power LED, the improvement of luminous efficiency is also related to the choice of phosphor and processing. In order to improve the efficiency of blue chip excited by phosphor, the phosphor must be selected properly, including excitation wavelength, particle size, excitation efficiency and so on. Secondly, the fluorescent powder coating to be uniform, preferably relative to the light-emitting chip surface of the glue layer thickness uniformity, so as to avoid uneven thickness caused by local light can not shoot, but also improve the quality of light spot./n/n /n/n4. Reflection processing/nThere are two main aspects of reflection processing, one is the internal reflection processing of the chip, the other is the reflection processing of the packaging material to the light, through the internal and external reflection processing, to improve the ratio of the light passing out from the inside of the chip, and reduce the internal absorption of the chip, improve the luminous efficiency of power LED products. In terms of packaging, power LED chip is usually assembled on a metal bracket or substrate with a reflective cavity. The reflective cavity of the bracket is usually electroplated to improve the reflective effect, the reflective cavity of the substrate type is usually polished and electroplated, but the two methods are affected by the precision of the mould and the technology. The reflective cavity after treatment has a certain reflective effect, but it is not ideal. At present, the reflective cavity of the substrate type is made in China, because of the low polishing accuracy or the oxidation of the metal coating, the reflective effect is poor, which causes a lot of light to be absorbed after it hits the reflective area, and it can not reflect to the light surface as expected, therefore, the light-taking and light-transmitting efficiency of the final package is on the low side./n/n

TAGS: