Detailed LED radiation loss during use

Introduction: LED RAM MCU system commonly used testing methods is called the fourth generation light source or green light, has the characteristics of energy saving, environmental protection, long life, small size, can be widely applied in various directions, display, decoration, backlight, general lighting and city lights and other fields. In recent years, some developed countries in the world have launched a fierce competition in the field of LED.

The light output rate determines the degree of application of LED light source

LED lighting and traditional lamps have a completely different structure, and the structure has a Guan Jian effect on its characteristics, modern LED lamp is mainly composed of LED light source, optical system, organ, radiator, drive interface standard lamps of five parts. In Germany, the nano particles can be used to increase the refractive index by more than 1.8, reduce the light scattering, improve the efficiency of LED and improve the quality of light. Usually the fluorescent powder size in the 1um above the refractive index is greater than or equal to 1.85, and the refractive index of silica gel is generally around 1.5, because both refractive index mismatch and phosphor particle size is much larger than the optical scattering limit (30nm), and the surface of phosphor particles in light scattering, reduced light rate.

At present, white LED is mainly realized in three forms:

1, the use of red, green, blue three color LED combination light-emitting multi chip white LED;

2, the blue LED chip and $phosphor by the blue light and yellow and white or white with complementary get blue LED chip with red and green fluorescent powder, blue light emitted by the LED chip, the phosphors emit red and green colors by mixing white light;

3, the use of ultraviolet LED chip issued by the near UV excitation of the three primary phosphor to get white light.

Detailed LED radiation loss during use

Currently widely used in second ways, the use of blue chip LED and $phosphor, complementary white light. Therefore, this chip can improve the lumen efficiency of LED, which is decided by the initial luminous flux and optical maintenance rate. The initial luminous flux of the blue chip LED is enhanced with the development of the epitaxy and substrate technology. Lumen maintenance light is kept by the packaging technology, keep the luminous maintenance rate is the key to improve the conductivity and heat environment, which relates to the key technologies of LED packaging: packaging process and low thermal resistance and high light taking rate of package structure and process. For now, the existing LED light efficiency level, due to 80% of the input energy into heat, so the chip heat dissipation is critical. The thermal resistance of LED mainly includes the internal thermal resistance and thermal resistance.

The radiating base is the main function of the absorption of the heat generated by the chip, and transmitted to the thermal resistance, realize heat exchange with the outside world; and reduce the interface and interface contact resistance, enhanced heat dissipation is the key, so the thermal interface material chip and radiating base is very important to select, the commonly used low temperature or eutectic solder paste or silver glue. The thermal conductive adhesive used in the LED chip used in the German lighting is the thermal conductivity of the nano particles, which effectively improves the interface heat transfer, reduces the interface thermal resistance, and accelerates the heat dissipation of the LED chip.

In the process of using LED, there are three main aspects of the loss of photons emitted by the radiation recombination:

1, the internal structure of the chip and the absorption of the material, the photon in the exit interface due to the refractive index difference caused by the reflection loss;

2, the total reflection loss caused by the incident angle is greater than the total reflection critical angle;

3, by covering the surface of the chip with a relatively high refractive index of the transparent layer can effectively reduce the loss of photons in the interface, improve the light extraction rate.

Therefore, it is required to have high light transmittance, high refractive index, good thermal stability, good fluidity, easy to spray, the same is to improve the reliability of the LED package it requires low moisture absorption, low stress and aging characteristics. And usually white LED also required the blue light emitting chip $phosphors, the packaging adhesive in the need to add $phosphor ratio of mixed color, so the excitation efficiency and conversion efficiency of phosphors with high luminous efficiency is the key.