Detailed design of UV-LED structure

Currently single, unlike UV-LED chip white chip, its power is very limited, so in order to obtain high power and high-power UV-LED devices enable stable and reliable work, but also to achieve a simple and compact package, it must be made UV-LED array design. That is, a plurality of UV-LED chip in a small module, to thereby obtain a larger light intensity light source. Using COB packaging technology, we can minimize the contact layer from the chip to the external environment, thereby reducing the thermal resistance, reduce material mismatch. With external cooling, it can make high-power UV-LED chip holding long persistently high brightness light emitting at a lower temperature, to ensure the reliability and stability of UV-LED light source.

 

Be UV-LED spot light structural design, the influence of UV-LED light efficiency are: 1) for the light reflected by the reflecting cup structure; 2) light transmittance and the refractive index of the lens through; 3) packaging technology is good or bad ; UV 4) packaging materials aging ability. These parameters will directly affect the UV-LED light extraction efficiency, UV-LED if the package is not designed reflector inside the cup, then the loss of a large portion of the light is converted to heat, which indirectly increases the thermal management more difficult.

 

Currently UV-LED main epoxy resin and silicone / glass lens package. The former is mainly used in more than 400 nm in the near-ultraviolet LED package, which is mainly used wavelength of less than 400 nm LED package. Also, because the refractive index of GaN and sapphire, respectively, 2.4 and 1.76, and a refractive index of a gas, a large refractive index difference leads to total reflection of light to escape more serious restrictions, encapsulated low light efficiency of the device. Therefore, in the design of the lens, to consider the device in light transmittance, heat resistance and resistance to UV ultraviolet aging ability.

 

According to the principle of light extraction, the two structures are made of a high refractive index of silica gel and glass lens, fully eliminate the effect of total reflection of light, greatly improving the light efficiency. These two structures are very similar, are the solid crystal LED chips directly on a ceramic substrate, a ceramic substrate via solder balls on soldering copper and aluminum heat sink or heat sink, the thermal resistance of the entire package is small, the refractive index of the outer package 1.5 of silica gel and glass lens, reflector plate ceramic substrate comes reflector cavity, the only difference is that the latter pay more silica layer package B, three-layer structure having a refractive index decreasing, reducing total reflection of light loss.

 

In the whole package, the resin layer thickness are thin, silicone can minimize ultraviolet absorption loss, and the refractive index layer decreases the three-tier structure helps to reduce the propagation of light in the Fresnel loss . In some cases, improve the light transmittance For more, can all plating in the surface of the optical system of the optical antireflection coatings.

 

In the package, the design reflecting cavity is particularly important. In order to achieve the optimum light intensity, the reflection angle of the reflective cavity should be the best reflection angle 55 °, or the angle between the cavity of 70 °, the reflection angle is too large or too small will result in the emission intensity decrease.

 

Also, according to the principles of optics on the light, in order to effectively reduce the total reflection phenomenon, we chose the principle of the glue is generally from the inside to the outside, glue refractive Low (refractive index of the outer layer of glue can be less than or equal to the inner glue refraction rate, but never higher than the refractive index of the inner layer of glue).

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