Abstract: The application of white LED lighting in the area more and more widely, in particular, LED energy-saving environmental protection has been recognized by the world, how to enhance the life of white-light LED white light LED reduce the attenuation of a package of research and development issues, this white LED to improve for the material aspects of decay.
Keywords: white LED; Chip; solid crystal underfill; phosphor; fluorescent plastic; stent.
The advent of blue LED using the phosphor and blue LED combination, you can easily get white LED, which is the most mature industry, a white package. Now has become a white LED light source, the general household lighting has become a reality. But in the course of attenuation of more white products, not suitable for the lighting market, the Lehman high-end optical market demand for lighting, increase the white light of the development, packaging technology and materials by changing with the development of low attenuation white products, LED lighting industry a little to make modest. Here is the package during our five-point summed up the experience, industry colleagues share with you to the white LED packaging technology to enhance building blocks.
First, the chip white LED light on the impact of failure
From the current experimental results, the impact of bad light chip divided into two categories: first, different materials result in attenuation of the chip is different from the commonly used substrate material for blue-chip silicon carbide and sapphire, silicon carbide general structure deSigned as a single electrode, the thermal effect is better, sapphire general design for the two-electrode, heat is more difficult to export, thermal conductivity less effective; the second is the size of the chip, the same material in the chip, the size gap between the different decay is also different.
Second, solid-bottom plastic crystal white LED light failure on the impact of
In the white LED packaging industry crystalline solid usually used in insulating plastic with epoxy adhesive, silicone rubber insulation, silver plastic. Three advantages and disadvantages, should be taken into account in the selection of the time. Poor thermal conductivity epoxy adhesive insulation, but the high brightness; silicone rubber thermal insulation effect of slightly better than the epoxy resin, high brightness, but a certain percentage of the silicon component accounted for, when the chip next to the residual solid silicone rubber in the ring with the fluorescent the combination of epoxy resin insulation layer phenomenon occurs when, after a cold shock led to death of light peel will produce; silver thermal conductivity of plastic are better than the first two, you can extend the life of LED chips, but the light absorption of silver colloid large, resulting in low brightness. The blue-chip dual-electrode in the solid crystal with a silver plastic, the plastic volume control on very strict, otherwise easily lead to short-circuit a direct impact on product yields.
Third, the phosphor white LED light on the impact of failure
White LED to achieve a variety of ways, the current most widely used one is the most mature in the blue chip by applying a layer of yellow phosphor, the blue and yellow mixed into white light, so the material of the white LED phosphor attenuation of significant influence. Market is the most mainstream YAG phosphor is yttrium aluminum garnet phosphor, silicate, nitride phosphor, compared with the blue LED chip white LED phosphor has the role of accelerated aging, and the phosphor of different manufacturers lumen is not the same degree of influence, which is closely related to the phosphor composition of raw materials. Lehman Optical White Phosphor choose the best materials, made of white LED compared to counterparts in the attenuation control has been greatly improved.
Fourth, the glue on the white LED light fluorescence decay of
Traditional package of white LED, fluorescent plastic commonly used epoxy or silicone, after bad light experimental results obtained with silica gel powder with white LED life span significantly longer than the epoxy resin. One reason is packaged with the above two methods into a finished LED, UV resistant silicone ability than the epoxy resin and silicone resin heat better than good; but in the same condition, with silica gel powder with the initial brightness than the ring epoxy resin powder with a lower, mainly due to the refractive index of silica (1.3-1.4) than the epoxy resin (1.5 or above) is low, so the epoxy is less than the initial high light efficiency.
Fifth, Support the white LED light decline of
LED stent mainly copper and iron bracket bracket. Thermal conductivity of copper bracket, conductive performance, high price. The iron frame of the thermal conductivity, electrical conductivity is relatively poor, more likely to rust, but the price is cheap. Most LED on the market use of iron bracket. LED support on different materials have different performance impact, especially in light of decline is particularly prominent. This was mainly due to the thermal conductivity of copper a lot better than iron, copper, thermal conductivity of 398W (mk), while the thermal conductivity of iron is only 50W (mk) about the former is only 1 / 8, as well as support the plating thickness also closely related. In the selection of scaffolds, but also pay attention to whether the support of the bowl cup size particles with light-emitting chip and die match, the match quality of the pros and cons of a direct impact on the optical effect of white light LED, or likely to cause asymmetric spot shape, a yellow circle, and spots, etc., directly affect the quality of the product.
With the white LED for Lighting applications, customer demand is also rising, we must constantly innovate and upgrade our technology to improve our performance as much as possible to meet customer needs. To make high-performance white LED products, materials selection and mix is the best direct impact on decay and quality of white light LED, so good with the best mix of materials, coupled with the manufacturing process, some Leiman Te technology is the key to good white light. Lehman people, we must give full play to their advantages, continue efforts to increase R & D to develop more suitable for customer requirements for the country's semiconductor industry to contribute to Energy saving lighting.
