OFweek semiconductor lighting network: advent blue LED, a phosphor using a combination of a blue LED, white LED can easily be obtained, which is one of the most mature industry white light package. At present, white LED has become an illumination source, and general household lighting has become a reality. However, during the use process, more white light products have a large attenuation and cannot be suitable for the lighting market. Lehman Optoelectronics has increased the research and development of white light for the high-end market demand, and developed low-attenuation white light products by changing the packaging process and material matching. The lighting industry is slightly weak. The following are the five points that the author summed up in the packaging process, and communicated with colleagues in the industry, in order to add to the improvement of white LED packaging technology.
First, the impact of the wafer on the light decay of white LED
From the results of the current experiments, the effects of wafers on light decay fall into two broad categories:
The first is that the material of the wafer is different, resulting in different attenuation. Currently, the commonly used blue wafer substrate is made of silicon carbide and sapphire. The general structure of silicon carbide is designed as a single electrode, and its thermal conductivity is better. The sapphire is generally designed as a double electrode, which is difficult to heat. Export, the thermal conductivity is poor;
The second is the size of the wafer. When the material of the wafer is the same, the difference in size is different.
Second, the effect of solid crystal primer on the light decay of white LED
The solid-state adhesives commonly used in the white LED packaging industry are epoxy resin, silicone resin, and silver glue. Each of the three has its own advantages and disadvantages, and should be considered comprehensively when selecting. Epoxy resin insulation has poor thermal conductivity, but high brightness; silicone resin has better thermal conductivity than epoxy resin, and has high brightness. However, due to the proportion of silicon component, the silicone resin and the ring in the fluorescent rubber remain on the side of the solid wafer. When the oxygen resin is combined, the interlayer phenomenon will occur. After the thermal shock, the peeling will cause the dead lamp; the thermal conductivity of the silver gel is better than the former two, which can prolong the life of the LED chip , but the absorption of light by the silver paste is compared. Large, resulting in low brightness. For the two-electrode blue chip, when the crystal is fixed with silver glue, the control of the amount of glue is also very strict, otherwise it is easy to generate a short circuit, which directly affects the yield of the product.
Third, the effect of phosphor on the light decay of white LED
There are many ways to realize white LEDs. The most common and most mature one is to mix blue and yellow light into white light by applying a yellow phosphor on the blue light wafer. Therefore, the material of the phosphor is attenuated by white LEDs. great influence. The most popular phosphors in the market are YAG yttrium aluminum garnet phosphors, silicate phosphors, and nitride phosphors. Compared with blue LED chips, phosphors have the effect of accelerating aging white LEDs, and phosphors from different manufacturers The degree of influence of fading is also different, which is closely related to the raw material composition of the phosphor. Lehman Optoelectronics uses the best material white phosphor, which makes the white LEDs have a great improvement in attenuation control compared with their peers.
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