Brief Analysis of High-Power LED System Integrated Packaging Technology

As the global energy shortage trend becomes increasingly serious, green, energy-saving and environmentally friendly LEDs have attracted much attention. Countries around the world have formulated their own LED lighting development plans. my country's "12th Five-Year Plan" also clearly describes the development goals of LED lighting and lists LED as a key energy-saving project during the "12th Five-Year Plan", ranking it among the energy-saving and environmental protection industries and new materials industries among the country's seven strategic emerging industries.

　　With the development of the LED lighting industry, a relatively complete industrial chain has been formed from the production of LED chips to the lighting market. However, for traditional LED lighting, from chips, packaging, circuit boards to applications, each link is relatively independent. The lighting needs of different places have put forward various new requirements for LED packaging. How to integrate multiple technologies in the module and make the LED module packaging miniaturized, multifunctional and intelligent through system packaging has become a problem we need to explore. From a technical point of view, LED is a semiconductor device that can be easily combined with other semiconductor-related technologies to develop products with higher added value and open up a new market that traditional lighting cannot reach. LED multifunctional system three-dimensional packaging can integrate light sources, active and passive electronic devices, sensors and other components, and integrate them into a single miniaturized system. It is a new technology with great market potential.

　　LED multifunctional packaging integration technology

　　At present, there are some simple LED integrated packaging products on the market, but the integration is low and cannot meet the needs of LED light-emitting modules for LED packaging products in the future. The development trend of chip module light sources reflects the requirements of the lighting market for technological development: portable products require more integrated light sources; in the fields of commercial lighting, road lighting, special lighting, flashlights, etc., integrated LED light sources have a large application market. Compared with package-level modules, chip-level modules are smaller in size, save space, and also save packaging costs. In addition, due to the high integration of the light source, it is convenient for secondary optical design.

　　Three-dimensional packaging is an electronic packaging technology that has developed in recent years. Generally speaking, the important factors that accelerate the application of three-dimensional integration technology in microelectronic systems include the following aspects:

　　1. System size: reduce system size, reduce system weight and reduce the number of pins;

　　2. Performance: Improve integration density and shorten interconnection length, thereby increasing transmission speed and reducing power consumption;

　　3. High-volume and low-cost production: reduce process costs, such as adopting a mixed use of integrated packaging and PCB; packaging multiple chips at the same time, etc.;

　　4. New applications: such as ultra-small wireless sensors, etc.;

　　There are many different advanced system integration methods, mainly including: package stacking technology on package; chip stacking on PCB (wire bonding and flip chip), stacked flexible functional layers with embedded devices; advanced printed circuit board (PCB) stacking with or without embedded electronic devices; wafer-level chip integration; vertical system integration (VSI) based on through-silicon vias (TSV). The advantages of three-dimensional integrated packaging include: using different technologies (such as CMOS, MEMS, SiGe, GaAs, etc.) to achieve device integration, that is, "hybrid integration", usually using shorter vertical interconnects instead of very long two-dimensional interconnects, thereby reducing system parasitic effects and power consumption. Therefore, three-dimensional system integration technology has great advantages in performance, function and shape. In recent years, key universities and research and development institutions have been developing different types of low-cost integration technologies.

　　The National Key Laboratory of Joint Innovation of Semiconductor Lighting has also conducted systematic research on LED system integration packaging. This research is aimed at LED downlights. By developing wafer-level packaging technology, it plans to integrate some driving components and LED chips into the same package. Among them, the bare chips required for LED and linear constant current drive circuits are the main components of circuit heating. At the same time, they are relatively small and easy to integrate, but since they are the main heating components, heat dissipation design needs to be considered. Other components are large in size and not easy to integrate. Inductors, sampling resistors, fast recovery diodes, etc., although they also generate a certain amount of heat, do not require special heat dissipation structures.

　　Based on the above considerations, we designed the assembly of the light-emitting module as follows:

　　1. The driver circuit die and LED chip are integrated in the package, and the remaining circuit components are integrated on the PCB board;

　　2. The PCB circuit board surrounds the integrated package for easy connection;

　　3. The PCB and integrated package are placed on the heat sink;

　　The advantages of this structure are: small size; the main heat-generating components are directly in contact with the heat sink through the package, which is easy to dissipate heat; components that do not require special heat dissipation can be placed on ordinary PCBs. Compared with MCPCB, it saves costs; when necessary, the components can be designed on the back of the PCB board and hidden in the empty area of ​​the heat sink to avoid the influence of the components on the light output.