Focus on COB package integrated COB into focus

Advantages of an integrated COB package

In fact, the integrated COB package has been popular for a while, and then returned to silence, but from 2011, the integrated COB package is once again "favored". In this regard, some industry experts said that the COB package was once popular because people were more Many places consider the simplicity and cost advantages of structure and application, but when there is a temporary threshold that can't be exceeded in terms of technology maturity, manufacturing process, material supply, product performance and reliability, it will be silent. Since 2011, the technology of COB light source packaging has been greatly improved, the manufacturing process has become more mature in industrialization, the material supply has been well protected, and the performance and reliability of light source products have been significantly improved, which has once again received attention. Very normal.

"COB package can divide one or two large chips into more than a dozen small chips, which can be made smaller and the horizontal heat dissipation efficiency is higher. From the perspective of vertical surface, the COB package can achieve better efficiency under a limited volume. Therefore, it has a relatively good performance in both horizontal and vertical heat dissipation," Zhao Zi, manager of the light source development department of Everlight Electronics Industry Co., Ltd. said in an interview. In addition, the integrated COB package has advantages in terms of heat dissipation, brightness and quality, color rendering and application. For example, the COB modular package form can reduce the bonding layer and reduce the overall thermal resistance in the structure; multiple chip support can help the brightness increase; reasonable chip configuration can enhance the optical effect; and in application, the package The steps include four main steps: material preparation, welding, assembly, and molding. It takes only 120 seconds from module to assembly.

The cost advantage is also the focus of the integrated COB package. According to industry insiders, compared with the traditional LED SMD chip package and high power package, the COB package can directly package multiple chips on the metal-based printed circuit board MCPCB. By directly dissipating heat through the substrate, the manufacturing process of the bracket and its cost can be reduced. “COB package forms a circuit connection by directly bonding or soldering the chip to the heat sink. Only one package can simplify the secondary light distribution, which has a cost advantage and is about 30% lower than the cost of the general LED package”. However, some industry experts said that the cost of integrated COB package itself does not necessarily have obvious advantages compared with the device light source, but the comprehensive cost of lighting application is low; the performance of COB light source with different technical solutions has its own performance and reliability. Most of the advantages of the device light source are not obvious, but some solutions have shown obvious advantages (such as about 20% improvement in light efficiency).

There are still a series of problems that need to be solved

Up to now, the integrated COB package has made many advances in substrate technology, packaging technology, detection technology, chip technology, etc. However, there are still some problems to be solved in the integrated COB package, such as low production efficiency and direct production yield. Low-level, light-color chromaticity consistency control is difficult, COB package light source still has standardization problems, and the package manufacturer and the lighting finished product factory standard cannot be docked. At present, the integrated COB package has problems of low light efficiency, heat dissipation performance and yield improvement. On the one hand, COB light efficiency is low. The integrated package has low light efficiency, generally 20% to 30% lower than the independent package; the light loss and thermal energy increase defects caused by multiple refraction of the primary optical lens are to be improved; currently, the integrated COB package light source mostly uses an aluminum substrate as a material, aluminum The thermal conductivity of the substrate COB is large, the reliability is not high, and the phenomenon of light decay and dead light is prone to occur. On the other hand, the heat dissipation of the COB package needs to be improved. The concentration of the COB light source is high, and if the heat of the light source cannot be exported in time, the life of the light source will be shortened. In addition, the yield rate has room for improvement. For example, the poor process environment and low operating level have a great impact on the overall package out-of-control rate, and the level of the solid crystal bonding wire needs to be improved. For the solution of these problems, some insiders believe that the light effect can be improved by improving the reflective efficiency of the package holder and the substrate, increasing the groove structure layer and adopting multi-cup integrated COB packaging technology. At the same time, the ceramic substrate can be widely used and the substrate can be improved by using the dielectric layer heat dissipation function MCPCB, and the yield can be improved by using a device with higher precision and stability and improving the hardware environment of the COB packaging factory. However, some insiders also said that although the ceramic substrate is one of the ideal materials for COB, the cost is high, especially when the power is small, it is difficult to be accepted by customers.

In addition, MCOB (multi-cup integrated COB package) is also a hot spot at present. MCOB directly puts the chip in multiple optical cups for encapsulation, improves luminous flux, and can also conveniently realize LED surface-emitting package, increasing the power of a single light source. Limit the glare and zebra pattern to improve the light efficiency per watt. Industry experts said that MCOB has made some improvements in substrate and soldering technology, such as the use of pure metal substrates coated with high-reflection film, and the use of aluminum wire for chip electrode connection. The COB light source has obvious advantages in light efficiency improvement, and has certain advantages in heat dissipation. However, since the metal substrate is a good conductor, it is difficult to realize the safety requirements in lighting applications. In addition, the expected cost reduction of metal substrates is limited, which has brought certain constraints to a large number of general lighting applications. Whether it can become a mainstream trend depends on whether there are any better technological breakthroughs and solutions in the near future.

At present, there are enterprises at home and abroad involved in integrated COB packaging. For the difference of technology at home and abroad, industry insiders said that the domestic and foreign integrated COB light source packaging models are not the same, domestic metal substrate packaging is the main, foreign mainly ceramics The substrate is mainly packaged, the technical route is different, the key materials used are different, and the technical level and product performance and price are not absolutely comparable. In general, foreign companies have advantages in product standardization, application specifications and technical support, while the domestic market is still in a state of disorderly development.

Whether it is mainstream or not, the market needs to have the final say

On the basis of technological advancement, the call for integrated COB packaging is a high trend in the future. Many companies in Japan and China have adopted the COB packaging model. "SMD technology has been applied since the earliest previous mobile phone backlights, and COB packaging is more customized. The lighting market needs more tailored specifications according to customer needs. Products, which require the packaging factory to achieve a good package in a relatively small area, high density. The start of the lighting market provides a good opportunity for the conversion of the package form from SMD to COB. Light, many companies are preparing to transfer most of SMD to COB packaging," Zhao said.

For the COB packaging market, some industry experts pointed out that the market demand for integrated COB packaging is gradually forming a stage, and it is still in the situation of some pioneering companies investing in stone and crossing the river. Applications should cover most LED lighting applications, but large-scale applications will not wait until the relevant standards and specifications are formed. Replacing the specifications of traditional lighting products requires the coordination of the middle and lower reaches of the industry chain to be clear, and ultimately the market must have the final say.

"The key to future competition lies in the standardization and cost-effectiveness. For enterprises, they should fully understand the market demand; solve the immature technology, form a relatively fixed process technology solution; solve the basic materials, key equipment problems, improve production efficiency and Product yield, focus on reducing costs; from the perspective of the entire industry, it is necessary to guide the middle and lower reaches of the industry chain to coordinate and form relevant norms and standards as soon as possible. For the future development of integrated COB packaging, experts in the industry suggest.