The biggest area of ​​the future LED market is the general lighting market. If it can completely replace fluorescent lamps, it is believed that there may be a potential market size of nearly $100 billion and it can be applied in more different fields. But in fact, if you expect LEDs to completely replace traditional light sources, there are still some difficulties. Since the LED is a point light source, some products can start to use LEDs instead of the bulbs of the past incandescent lamps. In actual market, there are already included ceiling lamps, interior lighting, etc., and the market scale is also yearly. Expanded. However, the market development in the field of surface light sources such as fluorescent lamps is relatively slow, because if the LEDs are to be used as surface light sources, the LEDs can only be covered on the fixed surface in a straight manner like the backlight for the panel, or This is done by using a light guide plate in a side light manner. However, these methods are difficult to replace fluorescent lamps in terms of luminous power and price, especially in the field of general illumination, which requires high color rendering, which requires the use of ultraviolet light or the use of blue LEDs to excite RGB fluorescence. Powder, but this will cause a decline in luminous efficiency, so it will take some time to meet the industrialized 100 lm/W lighting efficiency requirement.
Semiconductor lighting costs are gradually declining
This part is written by Professor Jiang Fengyi of Nanchang University in "China Electronics News" (11/2005). It is of great benefit to know the cost structure and development trend of LED white light lighting.
There are many technical routes for semiconductor lighting, and different technology routes cost differently. In terms of the same technical route, there are also significant differences in the cost of different technical levels. Even with the same technical route and the same technical level, each manufacturer adopts different cost control methods, and the results will be quite different.
Since the above problems all bring difficulties to cost prediction, the cost prediction of semiconductor lighting is required, and some assumptions are made on the technical solution: First, the blue LED excites the phosphor, wherein the blue LED is a GaN-based multiple quantum well LED structure; secondly, The chip is packaged into a single lamp by a chip having a size of 1 mm×1 mm; thirdly, the semiconductor lighting lamp is simply combined by a plurality of single lamps; and fourth, each single lamp is mounted on a lamp bracket with a driving power source and good heat dissipation performance. However, the cost of driving power supplies, brackets and decorative parts is not counted in the cost of solid-state lighting, that is, only the cost of "bulbs" is considered; fifth, the efficiency of chip illumination and the power density that chip devices can withstand are basically the same. Cost has nothing to do. This assumption is true within a certain range. For example, the same research unit or enterprise can improve the epitaxial growth, chip manufacturing and device packaging level, and can significantly improve the luminous efficiency and the current density that the device can withstand by optimizing the process technology without significantly increasing the cost; Epitaxial growth, chip fabrication and device packaging have achieved an ideal 90% pass rate.
When the luminous efficiency is 40 lm/W, the cost of a 1W semiconductor white light lamp is less than 2.5 yuan, and the semiconductor white light with a luminous flux of 1500 lm should be controlled within 93.75 yuan. When the luminous efficiency is 200 lm/W, the cost of a 1W semiconductor white light lamp is Within 2.5 yuan, the semiconductor white light with a luminous flux of 1500lm should be controlled within 18.75 yuan; the luminous efficiency is up to 200lm/W, and the device power density is up to 10W/mm2 (the highest goal of the US solid-state lighting technology roadmap) That is to say, using a 1mm × 1mm GaN-based LED chip, it can be packaged into a semiconductor white light with a luminous flux of 2000lm, which is brighter than a 20W fluorescent lamp. At this time, compared with the fluorescent lamp, the cost of the 1500 lm semiconductor white light is lower, the cost of the main body depends on the package, and the cost may become less than 5 yuan.
Some countries have already made a plan for the cost of solid-state lighting technology. For example, the US solid-state lighting technology roadmap has a cost target: First, by 2007, a solid-state white light with a luminous flux of 200 lm (efficiency of 75 lm/ W), the price dropped below 4 US dollars, that is, the solid-state white light with the luminous flux equivalent to the level of 20W incandescent lamp, its unit price dropped to about 32 yuan; secondly, by 2012, the solid-state white light with luminous flux of 1000lm (lighting efficiency) For 150lm/W), the price dropped below US$5, that is, the solid-state white light with the luminous flux equivalent to 60W incandescent lamp, its unit price dropped to about 40 yuan; third, by 2020, the solid-state white light with luminous flux of 1500lm The lamp (lighting efficiency is 200lm/W), the price drops below 3 US dollars, that is, the solid-state white light with the luminous flux equivalent to the level of 20W fluorescent lamp, the unit price is reduced to about 24 yuan. (Note: This target may be formulated earlier. Nichia announced that it will launch LED products with a luminous efficacy of 150 lm/w in 2007. The development process of global LED lighting products is estimated to be much faster than the above target process)
At present, the market has a luminous flux of 30 lm to 50 lm of solid white light single lamp (1 mm × 1 mm chip), and its sales price is about 20 to 28 yuan. But what about the actual cost? On a sapphire substrate with a diameter of 50mm, the substrate, epitaxial and chip cost of GaN-based LEDs are 300 yuan, 300 yuan and 600 yuan, respectively. With this epitaxial material, 1600 power types of 1 mm × 1 mm can be fabricated. Semiconductor chips cost less than $1 per chip. At present, the cost of packaging 1W semiconductor white light is about 6 yuan (excluding chip cost), but mass production, manufacturers open their own models, cost control at 1.5 yuan is no problem, so as long as the scale of the enterprise is done, the pass rate is expected. Target, 1W semiconductor white light cost should be less than 2.5 yuan.
Whether this goal can be achieved, epitaxial material growth, chip fabrication and device packaging are equally important. The research work shows that the semiconductor lighting chip withstands the power density of 10W/mm2 is no problem, as long as the heat dissipation conditions are good enough, and the key problem in the future is to improve the quantum efficiency in the epitaxial material, improve the light extraction efficiency of the chip, and improve the device packaging efficiency and heat dissipation characteristics of the semiconductor. White light should replace incandescent and fluorescent lamps, and there is not much difficulty in the cost of epitaxy, chip and package. Even if the above forecast cost is doubled, it is still optimistic. The key challenge here is whether the technology level can be greatly improved. . Continuously improve the quality of epitaxial materials, continuously improve the luminous efficiency, continuously improve the power density that the device can withstand, and solve the problem of heat dissipation of devices. It is an inevitable trend to replace incandescent lamps and fluorescent lamps with semiconductor lighting lamps, and the price can be reduced to acceptable to ordinary people. degree. Recently, the technology at home and abroad has advanced by leaps and bounds, indicating that the era of semiconductor lighting entering thousands of households will come early.
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