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Small pitch packaging technology: SMD, COB, GOB, who will become the mainstream
Since the development of the LED display industry, a variety of production and packaging processes have emerged one after another. From the previous in-line (Lamp) process, to the surface mount (SMD) process, to the emergence of COB packaging technology, and finally to the emergence of GOB packaging technology.
In the development process of the small-pitch manufacturing process, many small-pitch manufacturers are trying to achieve the best solution for small-pitch displays.
SMD surface mount technology
SMD: It is the abbreviation of Surface Mounted Devices, which means: Surface Mounted Devices. LED products encapsulated by SMD (Surface Mount Technology) are packaged into lamp beads of different specifications with materials such as lamp cups, brackets, wafers, leads, epoxy resins, etc. Using a high-speed placement machine, the lamp beads are soldered on the circuit board by high-temperature reflow soldering to make display units with different pitches.
The small spacing of SMD generally exposes the LED lamp beads, or uses a mask. Due to the characteristics of mature and stable technology, low manufacturing cost, good heat dissipation effect, and convenient maintenance, it also occupies a large share in the LED application market. However, due to serious defects, it is unable to meet the needs of the current market.
1. Low protection level: no moisture-proof, waterproof, dust-proof, shock-proof and collision-proof. In humid climates, a large number of dead lights and broken lights are prone to occur. In the process of transportation, it is easy to drop the lights and the lights are broken. It is also susceptible to static electricity, causing dead lights.
2. Great damage to the eyes: long-term viewing will cause glare and fatigue, and the eyes cannot be protected. In addition, there is a "blue damage" effect. Because of the short wavelength and high frequency of blue LEDs, the human eye is directly and long-term affected by blue light, which is easy to cause retinopathy.
3. The LED lamp has a short lifespan: the lamp performance is affected by environmental factors, and the service life is greatly shortened. The PCB performance is affected by environmental factors and copper ions migrate, resulting in micro-short circuit.
4. Mask: Use the small distance between the SMDs of the mask and use it in a high temperature environment, and the mask is prone to bulge, which affects the viewing. After a period of use, the mask cannot be cleaned, causing whitening or yellowing on the spot, which not only looks ugly, but also affects viewing.
COB packaging technology
The full name of COB package is Chips on Board, which is a technology to solve the problem of led display for shop heat dissipation. Compared with in-line and SMD, it is characterized by saving space, simplifying packaging operations, and having efficient thermal management. COB packaging is to adhere the bare chip to the interconnect substrate with conductive or non-conductive glue, and then wire bond to achieve its electrical connection. If the bare chip is directly exposed to the air, it is susceptible to contamination or man-made damage, which affects or destroys the function of the chip, so the chip and the bonding wires are encapsulated with glue. This form of encapsulation is also called soft encapsulation. It has certain advantages in manufacturing efficiency, low thermal resistance, light quality, application, cost, etc.
However, as a new technology, COB has insufficient accumulation in the small-pitch LED industry, process details need to be improved, and the main products in the market are temporarily at a cost disadvantage.
1. Poor consistency: Due to the lack of the first step to select the lamp, the problems of inability to separate light and color, poor consistency, etc.
2. Serious modularization: Because it is composed of many small unit boards, the silent color is inconsistent and the modularization is serious.
3. Surface flatness: Because it is a single lamp dispensing, the flatness is poor, and it feels grainy.
4. Difficulty in maintenance: Due to the need for professional equipment, maintenance is difficult and the maintenance cost is high. Generally, it is returned to the factory for maintenance.
5. Manufacturing cost: Due to the high defect rate, the manufacturing cost far exceeds the small spacing of SMD
GOB packaging technology
GOB is the abbreviation of Glue on board. It is a kind of packaging technology. It is a technology to solve the problem of LED lamp protection. It uses an advanced new transparent material to package the substrate and its LED packaging units to form effective protection. . The material not only has ultra-high transparency, but also has excellent thermal conductivity. The small spacing of GOB can adapt to any harsh environment, and realize the characteristics of real moisture-proof, waterproof, dust-proof, anti-collision, anti-UV and so on.
Compared with traditional SMD, it is characterized by high protection, moisture-proof, waterproof, anti-collision, and anti-UV, which can be used in more harsh environments to avoid large-area dead lights and lights out.
Compared with COB, it is characterized by simpler maintenance, lower maintenance cost, larger viewing angle, horizontal and vertical viewing angles can reach 180 degrees, which can solve COB's inability to mix lights, serious modularization, spectroscopic color difference, poor surface flatness, etc. question.
The production steps of GOB series new products are roughly divided into 3 steps:
1. Select the highest quality materials, lamp beads, ultra-high brush IC solutions in the industry, and high-quality LED chips
2. After the product is assembled, before the GOB is poured, the lamp is aged for 72 hours and the lamp is tested
3. After GOB is filled with glue, it will be aged for 24 hours to confirm the product quality again.
In short, from the current situation: SMD packaging, COB packaging technology, and GOB packaging technology have their own advantages in the competition of small-pitch LED packaging forms. As for who can win the competition among the three, it depends on the advancement of technology and the market. degree of acceptance. The author speculates that GOB should be a transitional technology of COB technology. It is expected that by 2020, COB packaging technology should become mature and the cost will decrease. The future should be the world of COB.
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