How much is the UV-LED structure design of the "blue sea" crown flower damask

At present, a single UV-LED chip is not like a white chip, its power is very limited, so in order to obtain high power and make the high power UV-LED device stable and reliable work, and make the package structure simple and compact, it is necessary to propose the design of UV-LED array. In other words, the multiple UV-LED chips are integrated into a small module to get the light intensity of the light. Using COB packaging technology, the contact layer between the chip and the external environment can be reduced as much as possible, thus reducing the thermal resistance and reducing the problem of material mismatch. With the external cooler, the high power UV-LED chip can keep high luminance for a long time at lower temperature, and ensure the reliability and stability of the UV-LED light source.

Because the chip's luminescence is emitted from all directions of the chip to the outside world, when the UV-LED point light source structure is designed, the main effect of the UV-LED output is as follows: 1) the reflective cup structure for light reflection; 2) the light through the lens transmission rate and refractive index; 3) packaging technology; 4) packaging material. The anti ultraviolet aging ability of the material. These parameters will directly affect the efficiency of the UV-LED. If there is no design reflection cup in the UV-LED package, a large portion of the light will be lost and converted into heat, which indirectly increases the difficulty of heat management.

At present, UV-LED is mainly composed of epoxy resin package and silica gel / glass lens package. The former is mainly used in near UV LED packages with more than 400 nm, and the latter is mainly used in LED packages with wavelengths less than nm. The refractive index of GaN and sapphire is 2.4 and 1.76 respectively, and the refractive index of the gas is 1. The larger refractive index difference leads to the more serious escape of the total reflection limit light, and the efficiency of the device is low after the package. Therefore, in the design of the lens, the light transmittance, heat resistance and ultraviolet aging resistance of the device should be taken into consideration in the ultraviolet band.

According to the principle of light extraction, both of these two structures have used silica gel and glass lens with high refractive index, which fully eliminate the total reflection effect of light, and greatly improve the efficiency of light out. The two structures are very similar. The LED chip is fixed on the ceramic substrate directly. The ceramic substrate is welded on the copper aluminum heat sink or heat sink through tin ball. The thermal resistance of the whole packaging structure is small. The outer packaging has a silica gel and glass lens with a refractive index of 1.5, and the reflecting plate is the only zone with the ceramic substrate. It is not that the latter is added a layer of Encapsulated Silica B to form a three layer structure with diminishing refractive index, reducing the total reflection of the light loss.

In the whole package structure, the thickness of the resin layer is thin, and the absorption loss of the UV light can be reduced as much as possible. The three layer structure which decreases the refractive index is beneficial to reduce the loss of Finel during the propagation of light. In some cases, if the light transmittance is increased more, an optical antireflection film can be plated on all surfaces of the optical system.

In the above package structure, the design of the reflecting cavity is also particularly important. In order to achieve the best light intensity, as shown in Figure 3-5, the reflection angle of the reflected cavity should be 55 degree to the best reflection angle, or the angle of the cavity is 70 degrees, and the reflection angle too large or too small will lead to the decrease of the luminous intensity.

In addition, according to the optical principle of light out, in order to effectively reduce the total reflection phenomenon, the principle of choosing glue is generally from inside to outside, the refractive index of glue is from high to low (the refraction rate of the film can be less than or equal to the refractive index of the inner layer, but must not be higher than the refractive index of the inner glue water).