Gold Eletrode NTC Thermistor Chip Take Light Rate Package Structure and Process
In the NTC thermal gold electrodes / silver electrode chip in use process, 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. 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. 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 NTC thermal gold electrodes chip/silver electrode chip 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 NTC thermal gold electrodes chip/silver electrode chip 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, the thermal stress of silica gel internal increased, leading to lower the refractive index of silica gel, which affect NTC thermal gold electrodes chip/silver electrode chip efficacy and light intensity distribution.
The role of light color phosphor in compound, form white light. Its main characteristics including grain size, shape, semiconductor thermal efficiency, conversion efficiency, stability (heat and chemical), among them, the semiconductor thermal 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 the white light NTC thermal gold electrodes chip/silver electrode chip color 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, semiconductor thermal low efficiency. 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 thermal NTC gold electrodes chip/silver electrode chips out light efficiency (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 LumiNTC thermal gold electrodes chip/silver electrode chip company s development of 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, and will contain phosphor glass from the chip must be placed in position, not only improve components reliability, and greatly improve the efficacy (60%), as shown in figure 3 (c).
Overall, to improve thermal NTC gold electrodes chip/silver electrode chips out of light efficiency and reliability, encapsulation sub have gradually by high refractive index transparent glass or microcrystalline glass replace trends, through the will in the mixed or phosphor coating on the glass surface, not only improve the evenness of phosphor, but improve the encapsulation efficiency. In addition, reduce NTC thermal gold electrodes chip/silver electrode chips out the direction of the light optical interface number, also improve the efficiency of the light out effective measures.
