At present, the semiconductor LED as energy saving, environmental protection, the main technique has been incorporated into the national long-term technology development plan with the "Eleventh Five-Year" national "863" high-tech industries of major projects, and has been strongly supported. However, China's current development and application of LED products, many deficiencies still exist areas. China's own LED chips, wafer production is still limited, products mainly low-grade, large gap with foreign countries. Small-scale industry can only meet the domestic demand for packaging companies 20% -30%, most high-performance high-power LED and LED products have to rely on imports. In addition, the application of the LED market, there are also the product range, variety mixed constraints caused the problem, especially in the general lighting field, because of inadequacy of the technology so that it can not scale generalizable. Therefore, the promotion of LED packaging technology development efforts to enhance its own core technologies and achieve the scale of production is the development of LED industry, the most critical step.
A, LED lighting industry trends and analysis
1. High-power LED highlighting the rapid growth momentum has gradually become a mainstream product
In 2008, the global LED market reached 80 billion U.S. dollars, the LED products in the market share increased from 40% in 2001 to grow to more than 70% in 2005, including high brightness LED in the 1995-2004 average annual growth rate between 46%. U.S. market research firm Communications In-dustry Researchers (CIR) predicts that the global LED market size of the average annual growth rate of more than 30% in 2009, the market size will exceed 100 billion U.S. dollars. In recent years, with LED lighting, small-size panel backlighting, and interior lighting applications such as the gradual expansion of new, high brightness LED has been in the past few years, rapid growth stage, the LED will gradually increase in the proportion and has become the mainstream LED products.
2. Technological breakthroughs general lighting, lighting a huge opportunity to upgrade the engineering industry
The field of general lighting, lighting accounts for 90% of the market share. Following the semiconductor lighting as incandescent, fluorescent, energy saving lamp, the fourth generation of revolutionary new high efficiency solid light source, with a long life, energy saving, environmental protection and other significant advantages. LED application areas but mainly in the special lighting, the U.S., Japan, Korea, Europe, China and Taiwan in terms of LED technology have been launched special national research plan, if used for general illumination technology, once mature, will face a of 500 million lighting market share re-divide, so lighting a huge opportunity to upgrade the engineering industry.
3. China's LED lighting industry should be to package high-end products and product upgrades direction light
In the LED field, there are three elements, namely, the growth of light-emitting semiconductor wafer, chip and package. Currently there are three links in the low-end applications still have a certain foundation. But in the key, especially in the growth part of the wafer, and the world class level there is a large gap.
3.1 Necessity
At present, China's industrial advantages, mainly in packaging, regional distribution of output from the package, the output value of packaging in 2008, about 25 billion U.S. dollars, has already surpassed Japan, Taiwan became the world's largest packaging areas, and have the core competitiveness of the market and technology. But the attention of state and government which does not have much, if Taiwan and Japan and other countries from the economic crisis or out of remission at any time may form the dominance of Japan, Taiwan and the United States, Qi Jin, Europe and Korea in the "equal shares" of the distribution pattern We will once again lose the initiative and opportunity. Therefore, we should upgrade the existing industrial advantages, the high-end products to the packaging effort, while the direction of lighting technology in general more effort to break through barriers to technology patents LED industry, fostering competitive advantage in emerging markets.
(1) the current state for the entire LED industry chain focus on the upstream extension of the two chips and the downstream part of lighting applications. Gradually upstream investment funds have been great, but with little success, but the gap with the leading international upstream growing. Downstream products and also because product quality problems, uneven, difficult to ensure stable long-life use of effects. This will cause users to doubt China's LED products and more conservative and negative attitude. This feedback to all aspects of government leaders, and national attention to rectify the LED market before, the end result is a "halt", led to the need to spend a lot of manpower and national resources, the introduction of foreign advanced packaging technology of leading enterprises to guide the country downstream products, so we will once again lose the entire LED industry, the right to speak, the domestic market channels will be occupied by the form of OEM.
(2) up to now, because the four leading enterprises (CREE, PHILPS, OSRAM, Nichia Chemical) have different technical routes and patent monopoly protection, and the immaturity of their packaging and other reasons, so now the industry has not yet A LED light on the standards. If our advanced LED light source enterprises and units, especially those with core technology for high-power LED light source advanced enterprises and units in the government support and promotion, organization of scientific research personnel, conduct a new design and development of technical standards , adhere to the scientific practice and the basic principles of innovation and development will be in the global LED industry, at least in the upper reaches of this one made substantial breakthroughs. If participation in the international and guidance on the final development of international standards, will be the power of science and technology of China Aerospace Science and Technology, following the scientific initiative after another, thus directly in the LED industry, our country's international influence have changed the fundamental understanding, to a new level.
Second, high-power LED light source with the advantages of core technology
LED is generally from the wafer - silicon - light - lamp composed of four links, middle and lower reaches in the LED industry, the key point is how the application of thermal resistance and junction temperature to resolve such key issues as a prerequisite, to maintain a stable and effective chip light output.
All along, LED light source for general lighting applications, the existence of light metal material with high thermal conductivity problem, apply the heat balance, long-lasting fluorescent light problems and problems with bottlenecks in the four core technologies:
1 core technologies: metal material with high thermal conductivity
Currently on the swimming dragon enterprises, such as chips can be done CREE has luminous efficiency can reach 130-150lm / W. But the LED junction temperature directly affects the level of LED light extraction efficiency, device lifetime, reliability, emission wavelength. Maintain the LED junction temperature within the allowable range, is the preparation of high-power LED chips, packaged devices and device applications must focus on every aspect of the key factors, especially the application of LED device packaging and device design must focus on solving the core problem.
Applications are now mainstream to encapsulate the substrate material is aluminum, but aluminum plate package heat and light conversion efficiency of the chip are the core technology bottlenecks exist, can not effectively control the junction temperature and stable to maintain a high light output power and optical applications because of the chip The higher efficiency required the greater area of the aluminum plate will increase the cost and application size, very inconvenient. So how to get out of this misunderstanding of new paths is a central feature of the new technology.
Core Technology 2: heat balance technique
LED device structure with patented key technologies of heat balance cooling, and passive cooling in low-cost way to maintain the premise, the use of high thermal conductivity media, through the new device / light overall structure, succeeded in reducing the thermal resistance junction reduce the PN junction temperature, the PN Results of work within the allowable operating temperature to maintain the large number of photons output. Its characteristics are as follows:
(1) ultra-low thermal resistance material, the overall structure of rapid cooling techniques;
(2) high thermal conductivity, UV resistant packaging technology;
(3) application of low environmental stress structure technology;
(4) the overall thermal resistance of <20K / W, junction temperature "80 degrees;
(5) LED illumination control module operating temperature below 65 ℃.
3 core technologies: the application of efficient phosphor
Common on the market today phosphor white LED light application of technology is to GaN chip and yttrium aluminum garnet (YAG) package together to make the technology Nichia Chemical of Japan in the late 90s of last century invention, and the formation of patent monopoly. GaN blue chip fat (λp = 465nm, Wd = 30nm), high-temperature sintering of YAG containing Ce3 + phosphor, excited by this yellow and blue light emission, peak 550nm. Blue LED substrate cavity installed in the reflective bowl, cover with thin layer of resin mixed with YAG, about 200-500nm. LED blue part of the substrate to be issued by the phosphor absorbed, and some blue and yellow light emitted phosphor mixture can be too white. Theory for In-GaN/YAG white LED, by changing the chemical composition of YAG phosphor and adjust the thickness of the phosphor layer can be obtained color temperature 3500-10000K in colored white. But the traditional process based on white LED or blue with the LED, so when the color temperature is too high, the color will shift to the blue, and produce color drift, a certain light pollution. Must be used in reducing the light efficiency, lower overall thermal resistance of the circumstances, be achieved relative stability, but the decay is not optimistic.
The first has been the commercialization of products for blue chip with YAG yellow phosphor, the luminous efficiency of its best is about 35 lm / W, YAG and more Asian companies to Japan's import prices in 2000 yuan / kg ; The second is the Japanese Sumitomo Electric has developed the material to ZnSe white LED, but less luminous efficiency.
Core technology 4: LED time with the application of optical
The current global LED industry, the mainstream approach is the formation of the package LED light source or light source module chip after the time of the lamps made to conduct with light, so the original is used in the practice of traditional light sources, because the traditional light source is 360 ° . If you want the light guide to the application side, Philips is currently the best of a traditional lamp, the light loss is 40%. And our many domestic manufacturers of downstream applications, LED lamps are in fact the optical parameters of the optical parameters of the chip or the light source, rather than indicators of the overall parameters of the optical lamps.
Now the most advanced scientific method is done on the chip package with light, a light guide out of the chip to maintain maximum light output so that light loss rate of only 5% -10%. As technology continues to improve, the light loss rate will be lower and lower light source efficiency is increasing. Light source such as lamps with no need to do with light, the relative efficiency of the lamp will be greatly enhanced, making it more widely used to functional lighting, forming a considerable scale of the market channels.
