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Einleitung:
LED packaging refers to the packaging of light emitting chips. Compared with the integrated circuit packaging, it has a big difference. LED packaging not only affects the appearance and optical properties of the LED, but also directly affects its service life and reliability. Understanding the basics of LED packaging helps us to better choose the right package form and material, thus improving LED performance and reliability. In this article, let’s get to know some knowledge about LED packaging.
What is LED packaging?
LED packaging refers to the process of assembling the light emitting diode chip with supporting circuits, heat dissipation structures and other components, and sealing them with encapsulation materials to provide protection and heat dissipation. The main purpose of LED encapsulation is to encapsulate the exposed chip in an encapsulation body with protective features to extend the service life of the chip and provide good heat dissipation conditions.
Since the 1990s, LED chip and material production technology research and development has made a number of breakthroughs. Transparent trapezoidal substrate structure, textured surface structure, chip flip-flop structure, commercialization of ultra-high brightness of various colors of LED products have come to the market.
Starting in 2000 in the low and medium luminous flux of special lighting applications, LED upstream and midstream industries have received unprecedented attention, further promoting the development of downstream packaging technology and industry. Using different forms and sizes of encapsulation structure, different light-emitting colors of the tube core and its dual-color, or tri-color combination, can produce a variety of series, varieties, specifications of products.
LED packaging technology principles
High-power LED packaging due to the complex structure and process, and directly affects the performance and life of the LED. Especially high power white LED packaging is the hot spot in the research hot spot.The functions of LED packaging mainly include:
- Mechanical protection to improve reliability;
- Strengthen heat dissipation, in order to reduce chip junction temperature, improve LED performance;
- Optical control to improve light output efficiency and optimize beam distribution;
- Power management, including AC/DC conversion, and power control.
The selection of LED packaging methods, materials, structures and processes is mainly determined by factors such as chip structure, optoelectronic/mechanical characteristics, specific applications and cost. After more than 40 years of development, LED packaging has gone through the development stages of direct insertion pin type (DIP LED), SMD type (SMD LED), COB package (COB LED) and so on.
With the increase in chip power, especially the demand for the development of solid-state lighting technology, the optical, thermal, electrical and mechanical structure of the LED package has put forward new and higher requirements. In order to effectively reduce the thermal resistance of the package and improve the efficiency of light output, it is necessary to use new technical ideas for package design.
About LED packaging structure description
The core light emitting part of the LED is the pn junction core composed of p-type and n-type semiconductors. When the minority carriers injected into the pn junction are compounded with the majority carriers, visible, ultraviolet or near-infrared light is emitted. However, photons emitted from the pn junction region are non-directional, i.e. there is an equal chance of emission in all directions.
Therefore, not all the light generated by the core can be emitted, which depends on the quality of the semiconductor material, the core structure and geometry, the internal structure of the package and the encapsulation material. The application requires improvement of the internal and external quantum efficiency of the LED.
LED packaging materials
The selection of LED encapsulation materials is critical to LED performance and reliability. Common LED packaging materials include organic materials, inorganic materials and composite materials.
Organic materials mainly include epoxy resin, silicone, etc., with good light transmission and electrical insulation properties.
Inorganic materials mainly include aluminum nitride, silicon nitride, etc., with excellent thermal conductivity and high temperature resistance.
Composite materials are a combination of organic and inorganic materials, synthesizing the advantages of both.
Common LED packaging methods
DIP packaging (Dual In-line Package)
This LED package appeared in the late 1990s. This packaging technology consists of LED lamp beads directly into the PCB board, and then welded into the display module. Because the lamp beads below the two shaped like “feet” filament, can be directly threaded on the circuit board, so it is also called pin insertion. The process is relatively simple, the cost is relatively low, and it was widely used in the early days.
It is safe and stable. In the case of low voltage, it can be light, and low loss, high efficiency, long life, but also can be multi-color dimming. It is generally used for outdoor LED billboards, large stadium LED displays, plazas, shopping malls and other public places for outdoor displays.
SMD packaging (Surface Mount Devices)
SMD packaging technology emerged in 2002, and then gradually accepted by the market, and gained a certain market share. From pin seal surface mount packaging technology to SMD in line with the development of the electronics industry as a whole, many manufacturers launch such products. Surface mount packaging technology for P2-P10 point pitch packages is currently one of the most common packaging methods on the market.
The principle is to encapsulate the LED chip into a lamp bead, and then weld the lamp bead on the circuit board, made of different pitch LED module.SMD package LED each lamp bead is an independent point light source.SMD package technology has a long history of development, mature process, heat dissipation effect, and the production cost is relatively low.SMD package LED display can be used as indoor advertising display, stage background screen, and traffic control screen, etc.
COB packaging (Chip On Board)
COB packaging technology is to attach multiple bare LED chips directly to the PCB board and then seal the entire module completely. The process is simpler by eliminating the need for brackets, and a large number of pixels can be contained in a single package structure. Further reducing the dot pitch, products such as P1.25, P0.93, P0.78, etc. can be packaged with COB technology. Compared to the SMD process, COB also has more obvious advantages, showing a grain-free picture, a softer and clearer picture, and less prone to visual fatigue.
COB packaging reduces dot pitch characteristics, making it an ideal choice for indoor small pitch LED displays. Commonly used in fine control centers, command and control centers, high-end shopping malls, exhibitions and other places that require high-quality display.
From the cost and application point of view, COB packaging technology has become the mainstream direction of the future design of lamps and lanterns. COB packaged LED modules installed on the base plate of multiple LED chips, not only can improve the brightness, but also help to achieve a reasonable configuration of LED chips, reduce the input power flow of a single LED chip to ensure high efficiency.
GOB Packaging (Glue On Board)
GOB technology was initially launched for the protection of LED display beads and packaging technology. It adopts a new type of optical thermal conductive nano-filler material, and through special processes, the PCB board and SMD lamp beads of conventional LED display screen are encapsulated and matte double surface optical treatment.
Die GOB LED-Anzeige has excellent protection performance: waterproof, collision-proof, moisture-proof, dust-proof, anti-corrosion, anti-blue light, anti-salt, anti-static. Due to its relatively low integration, it is suitable for medium power applications.GOB LED display is usually used for stage rental, commercial advertising and security monitoring.
Schlussfolgerung
Overall, LED packaging technology is developing in the direction of diversification, different packaging methods have their own advantages and disadvantages and application areas. Each encapsulation technology has its own unique advantages and applicable scenarios, the choice of which technology depends on the specific application needs, cost considerations and technical requirements.
With the continuous development of LED technology, these packaging technologies will continue to innovate and optimize to provide better solutions for more applications.