Differences in LED packaging technology between Chinese and foreign companies

1. Overview The LED industry chain is generally divided into upstream, midstream and downstream, which are LED epitaxial chips, LED packaging and LED applications. As the link between the upstream and downstream of the LED industry chain, LED packaging plays an incomparable and important role in the entire industry chain. Various application products based on LED devices use a large number of LED devices, such as large LED display screens, LED backlight sources for liquid crystal displays, LED lighting fixtures, LED traffic lights and car lights. LED devices account for 40% to 70% of the total cost of application products, and the performance of LED application products is often more than 70% determined by the performance of LED devices.
China is a major LED packaging country. It is estimated that 80% of the world's LED device packaging is concentrated in China, distributed in various US-funded, Taiwan-funded, Hong Kong-funded and domestic-funded packaging companies.

In the past five years, foreign-funded LED packaging companies have been constantly relocating to the mainland, while domestic packaging companies have continued to grow and develop, and their technology has continued to mature and innovate. In the field of low-end and mid-end LED device packaging, Chinese LED packaging companies have a high market share, and in the field of high-end LED device packaging, some Chinese companies have made major breakthroughs. With the continuous maturity of process technology and the accumulation of brand reputation, Chinese LED packaging companies will surely play an important and leading role in China, a major country in LED application.

The following will explain these differences from the various links of the LED packaging industry chain.

2. Differences in packaging production and testing equipment

The main LED packaging production equipment includes die bonders, wire bonders, glue sealers, spectrophotometers, glue dispensers, smart ovens, etc. Five years ago, LED automatic packaging equipment was basically dominated by foreign brands, mainly from Europe and Taiwan, and China only had a small supply of semi-automatic die bonders and wire bonders. In the past five years, China's LED production equipment manufacturing industry has made great progress. Now, automatic die bonders, automatic glue sealers, spectrophotometers, glue dispensers, smart ovens, etc. are all available from manufacturers, with good cost performance.

The main LED testing equipment includes IS standard instrument, photoelectric comprehensive tester, TG point tester, integrating sphere lumen tester, phosphor tester, etc., as well as reliability test equipment such as thermal shock, high temperature and high humidity. Except for the standard instrument, which mainly comes from Germany and the United States, other equipment is currently produced and supplied by domestic manufacturers.

At present, among the LED packaging enterprises in China, the leading enterprises in scale all have the most advanced packaging equipment in the world, which is determined by the latecomer advantage. In terms of hardware level, the LED packaging enterprises above scale in China are the most advanced in the world. Of course, some higher-level testing and analysis equipment still needs to be further equipped.

Therefore, China has reached a world-leading level in packaging equipment hardware and has the foundation for the development of advanced packaging technology and processes.

3. Differences in LED chips

There are currently about ten LED chip companies in mainland China. They started late and are not large enough. The largest LED chip company has an annual output value of about RMB 300 million, and the average annual output value of each company is between RMB 100 and 200 million.

In the past two years, the LED chip companies in mainland China have developed rapidly and their technology levels have also improved rapidly. Small and medium-sized chips (below 15 mil) can basically meet the needs of domestic packaging companies. Large-sized chips (power-type W-class chips) still need to be imported, mainly from the United States and Taiwan companies. However, large-sized chips can only be used in large quantities after LEDs enter general lighting.

The performance of LED packaging devices depends on the LED chip to a 50% extent. The core indicators of LED chips include brightness, wavelength, failure rate, antistatic ability, attenuation, etc. At present, most of the small and medium-sized chips of domestic LED packaging companies are domestic brands. The performance of these domestic brands of chips is not much different from that of foreign brands, with good cost performance, and can also meet the needs of most LED application companies. In particular, the performance of some chip brands is comparable to that of foreign brands. Through the cooperation of packaging process technology, it can meet the needs of many high-end application fields.

4. Differences in packaging auxiliary materials

Auxiliary packaging materials include brackets, gold wires, epoxy resins, silicone, mold strips, etc. Auxiliary materials are an important basis for the comprehensive performance of LED devices. The quality of auxiliary materials can determine the failure rate, attenuation rate, optical performance, energy consumption, etc. of LED devices.

At present, the supply chain of packaging auxiliary materials in mainland China is relatively complete, and most materials can be produced and supplied in mainland China. However, high-performance epoxy resins and silicones are mostly imported. These two types of materials mainly require high temperature resistance, UV resistance, excellent refractive index and good expansion coefficient.

With the progress of global integration, Chinese LED packaging companies have been able to apply the world's newest and best packaging auxiliary materials.

5. Package design differences

There are three main types of LED packaging: bracket-type LED, surface-mount LED and power LED.

LED packaging design includes appearance structure design, heat dissipation design, optical design, material matching design, parameter design, etc.

The design of bracket-type LEDs is relatively mature, and currently there is room for further improvement in terms of attenuation life, optical matching, and failure rate.

The design of SMD LEDs, especially top-emitting TOP SMDs, is in constant development, with constant innovations in package bracket size, package structure design, material selection, optical design, heat dissipation design, etc., and has broad technical potential.

The design of power LEDs is a new world. As the manufacturing of large-size power chips is still under development, the structure, optics, materials, and parameter design of power LEDs are also under development, and new designs are constantly emerging.

China's LED package design is based on the improvement and innovation of existing designs in foreign countries and Taiwan. Design needs to rely on good computer design tools, good testing equipment and good reliability test equipment, and it also needs to be based on advanced design ideas and product comprehension. At present, China's LED package design level is still far behind that of foreign industry giants. This is also related to the lack of large-scale leading enterprises in China's LED industry and the lack of organized and planned large-scale R&D and design investment.

6. Packaging process differences

LED packaging process is also a very important link. For example, the glue quantity control of the die bonder, the wire temperature and pressure of the wire bonder, the temperature, time and temperature curve of the oven, the bubble and position control of the sealer, etc. are all key process control points. Even if the chip quality is good, the auxiliary materials are well matched, the design is excellent, and the equipment is high-precision, if the process is incorrect or the control is not strict, it will eventually affect the reliability, attenuation, optical properties, etc. of the LED.

With the rapid development of China's LED packaging companies in recent years, LED packaging technology has risen to a relatively good level, especially for some high-end demands such as large LED display screens, wide color gamut LCD backlight sources, etc. China's excellent LED packaging companies can already meet their needs, and LEDs produced by advanced packaging technology are close to the level of similar international products.

7. Differences in LED device performance

The performance indicators of LED devices are mainly reflected in the following six aspects:

①Brightness or lumen value; ②Luminous decay; ③Failure rate; ④Luminous efficiency; ⑤Consistency; ⑥Optical distribution characteristics

2. Light decay

Generally speaking, research shows that light decay is not closely related to chips, but is most closely related to packaging materials and processes. The packaging materials that affect light decay mainly include die-bonding glue, fluorescent glue, and external sealing glue, while the packaging processes that affect light decay mainly include the baking temperature and time of each process and material matching.

At present, China's LED packaging technology has a good foundation after years of development and accumulation, and is comparable to some foreign products in terms of light decay control.

3. Failure rate

The failure rate is related to chip quality, packaging auxiliary materials, production process, design level and management level.

LED failure mainly manifests as dead light, excessive light decay, excessive wavelength or color temperature drift, etc. According to the different application requirements of LED devices, there are also different requirements for their failure rate. For example, the failure rate of LED used for indicator lights can be 1000PPM (3000 hours); the failure rate of LED used for lighting is 500PPM (3000 hours); the failure rate of LED used for color display screens is 50PPM (3000 hours).

The overall failure rate of LEDs from Chinese packaging companies needs to be improved. Fortunately, the failure rates of a small number of excellent Chinese packaging companies have reached world standards.

4. Lighting effect

90% of LED light efficiency depends on the chip's luminous efficiency. Chinese LED packaging companies have also conducted extensive research on the technology to improve light efficiency in the packaging process.

If China achieves breakthroughs in the research and development and mass production of large-size watt-class chips, it will greatly promote the improvement of the luminous efficiency of power-type packaging devices.

5. Consistency

The consistency of LED includes wavelength consistency, brightness consistency, color temperature consistency, attenuation consistency, etc.

The consistency of the first three items can be achieved through material feeding process control and spectrophotometer screening. In terms of the first three levels, China's LED packaging technology is consistent with that of foreign countries.

Angle consistency is often difficult to sort out and needs to be achieved through optimized design, material mechanical precision control, and strict control of production processes. For example, the angle consistency control of the three elliptical LEDs, red, green, and blue, used in LED full-color displays is very important and has a decisive impact on the color quality of LED full-color displays, becoming a high-end technology for LED devices.

Attenuation consistency is also related to material control and process control, including the attenuation consistency of LEDs of different colors and the attenuation consistency of LEDs of the same color.

The study of consistency is an important topic in LED packaging technology.

The LED consistency technology of some Chinese LED packaging companies has been aligned with international standards.

6. Optical distribution characteristics

LED is a light-emitting device. For many LED applications, the light distribution of LED is an important indicator, which determines the design basis of the secondary optics of the application product and directly affects the visual effect of the LED application product.

For example, the LED oval lens design used in LED outdoor display screens can make the brightness of the display screen change smoothly when the angle changes and have a larger viewing angle, which conforms to people's visual habits. Another example is the optical requirements of LED street lamps, which require the primary optical design of LEDs and the secondary optical design of street lamps to match to achieve the best road surface light spot and the best luminous efficiency.

Computer optical simulation software is a common method for design and development. Chinese LED packaging companies are actively catching up and narrowing the gap with foreign technology.

8. Conclusion

As China becomes a major LED packaging country in the world, China's LED packaging technology is developing and improving rapidly, the gap with the world's top packaging technology is narrowing, and some products have surpassed it.

We need to increase R&D investment in the field of LED packaging technology research, and both enterprises and governments should pay attention to it. In fact, the gap between China's LED packaging technology and foreign countries lies mainly in the gap in R&D investment. As China's national strength grows, we believe that China will become a strong country in LED packaging.