2012-07-05

light rate encapsulation structure

High take light rate encapsulation structure and technology

In use process LED, radiation from the photon in composite to launch the generation when loss, mainly includes three aspects: chip internal structure defects and material absorption; In a photonic forms face because of losses caused by refractive index difference reflection; And the greater than the total reflection LinJieJiao Angle and cause of total reflection losses.online ups power manufacturer So, a lot of light can't from chip shots to the external. Through the chip surface coating a layer of refractive index relatively high transparent cover (pouring sealant was), because the fillet in chips and air between, thus effectively reduce the photons in the interface of the loss, improve the efficiency of take light.

High power white LED encapsulation structure

In addition, the role of the pouring sealant was also including the chips for mechanical protection, stress release, and as a kind of optical structure. So, ask its light transmittance high, high refractive index, and thermal stability, good fluidity and easy to spray. In order to improve the LED package reliability, also requires pouring sealant was with low hygroscopic, low stress, ageing resistance and other properties. Now commonly used pouring sealant was including epoxy resin and silica gel. Because of the high silica gel transmittance, refractive index, heat stability, and stress is small, hygroscopicity low characteristic, is obviously superior to epoxy resin, in high power LED packages to be widely applied, but cost is higher. Research shows that increasing the refractive index can effectively reduce the refractive index of silica gel physical barriers brought the photon loss, improve the quantum efficiency, but by environmental temperature on the performance of silica gel is larger. As the temperature increases,LED Products dab4d56ck the thermal stress of silica gel internal increased, leading to lower the refractive index of silica gel, which affect LED efficacy and light intensity distribution.

The role of light color phosphor in compound, form white light. Its main characteristics including grain size, shape, the luminous efficiency, conversion efficiency, stability (heat and chemical), among them, the luminous efficiency and conversion efficiency is the key. Research shows that, with the temperature rises, phosphor quantum low efficiency, reduce the light, radiation wavelengths will also be changing, and cause a white LED colour temperature, the change of the color and the higher temperature will accelerate the aging of phosphor. Reason is that the phosphor coating is by epoxy or silica gel and phosphor deployment and become, the cooling performance is poorer, when moving or by ultraviolet radiation, vulnerable to temperature sudden destroyed and aging, the luminous efficiency to reduce. In addition, high temperature and potting glue of phosphor thermal stability problems. Due to the commonly used in 1 um above phosphor size, refractive index is equal to or greater than 1.85, and silica gel refractive index generally in 1.5 or so. Because do not match between the refractive index, phosphor and particle size light scattering far limit (30 nm), so the phosphor particle surface exist light scattering, reduce the light efficiency. Through adding in silica gel nano phosphor, can make the refractive index increased to 1.8 above, reduce light scattering, improve the efficiency of LED light (10% 20%), and can effectively improve the quality of light color.

The traditional phosphor coating way is to phosphor and pouring sealant was mixed, then click coated in the chip. Due to the lack of phosphor coating thickness of the shape and precise control, causes a shoot the light color not consistent, appear blue or partial partial wall. And Lumileds company developed the form coating (Conformal coating) technology can realize the phosphor uniform coating, safeguard the uniformity of the light color, as shown in figure 3 (b). But research shows that, when phosphor coating directly in chip surface, caused by the scattering of existence, a light low efficiency. In view of this, the United States Rensselaer institute presents a Photon scattering Extraction process (Scattered Photon Extraction method, SPE), through in the chip surface decorate a lens,LED PAR Light and will contain phosphor glass from the chip must be placed in position, not only improve components reliability, and greatly improve the efficacy (60%),

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