What are the integration technologies for high-power LED multi-function packages?

With the increasing global energy shortage trend, green energy-saving and environmentally-friendly LEDs have attracted much attention. All countries in the world have formulated their own LED lighting development plans. China’s “Twelfth Five-Year Plan” also clearly describes the LED lighting development goals, and lists LEDs as key energy-saving projects during the “Twelfth Five-Year Plan” period, ranking seven national strategies. Energy-saving and environmental protection industries and new materials industries in emerging industries.

With the development of the LED lighting industry, from the production of LED chips to the lighting market, a relatively complete industrial chain has been formed. But for traditional LED lighting, from chip, package, circuit board to application, all aspects are relatively independent. The lighting requirements of different places have put forward various new requirements for the packaging of LEDs. How to integrate multiple technologies in the module and make the LED module package become smaller, more multifunctional and intelligent through the system packaging method has become a problem we need to explore. From a technical point of view, LED is a semiconductor device that is easy to combine with other semiconductor-related technologies to develop products with higher added value, opening up new markets that traditional lighting cannot reach. LED multi-function system 3D package can integrate light source, active, passive electronic components, sensors and other components, and integrate them into a single miniaturized system, which is a new technology with great market potential.

LED multi-function package integration technology

There are some simple LED integrated packaging products on the market, but the integration is low, which can not meet the needs of LED lighting modules for LED packaging products in the future. The development trend of chip module light source reflects the requirements of the lighting market for technology development: portable products require more integrated light sources; in commercial lighting, road lighting, special lighting, flashlights, etc., integrated LED light sources have great applications. market. Compared with package-level modules, chip-level modules are smaller, save space, and save packaging costs, and because of the high integration of the light source, it is convenient for secondary optical design.

Three-dimensional packaging is an electronic packaging technology developed in recent years. In general, the important factors that accelerate the application of 3D integration technology to microelectronic systems include the following:

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

2. Performance: Increase integration density and shorten interconnect length to increase transmission speed and reduce power consumption;

3. Large-scale low-cost production: reduce process costs, such as the use of integrated packaging and PCB mixed use solutions; multi-chip simultaneous packaging;

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

There are a number of different advanced system integration methods, including: package stacking technology on the package; chip stacking on PCB (wire bonding and flip chip), stacked flexible functional layers with embedded devices; with or without Advanced printed circuit board (PCB) stacking of embedded electronics; wafer level chip integration; TSV based vertical system integration (VSI). The advantages of 3D integrated packaging include: device integration using different technologies (such as CMOS, MEMS, SiGe, GaAs, etc.), ie "hybrid integration", which usually replaces long two-dimensional interconnects with shorter vertical interconnects, thus Reduce system parasitics and power consumption. Therefore, 3D system integration technology has great advantages in performance, function and shape. In recent years, various key universities and R&D institutions are developing different types of low-cost integration technologies.

The State Key Laboratory of Semiconductor Lighting Joint Innovation has also conducted systematic research on LED system integrated packaging. The research aimed at LED downlights, through the development of wafer-level packaging technology, plans to integrate some of the drive components and LED chips into the same package. Among them, the die required for the LED and the linear constant current driving circuit is the main component of the circuit heating, and the volume is relatively small, and it is easy to integrate, but the main heating element needs to consider the heat dissipation design. Other components are bulky and not easy to integrate. Inductors, sampling resistors, and fast recovery diodes , although there is a certain amount of heat generation, do not require a special heat dissipation structure.

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

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

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

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

The advantage of this structure is that the volume is small; the main heating element is directly in contact with the heat sink through the package, and is easy to dissipate heat; the component that does not require special heat dissipation is placed on the ordinary PCB. Compared with the MCPCB, the cost is saved; when needed, the components can be designed on the back side of the PCB and hidden in the empty area of ​​the heat sink to avoid the influence of the components on the light.