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At present, with the faster and faster pace of product updates and iterations, LEDs have also evolved from traditional SMD packaging to GOB packaging and then to the current high-end COB packaging. It sounds like these professional terms are difficult for people to understand what they mean except for professionalism? What kind of technology do they represent? Here, as a senior COB technical engineer of Maixinwei, I will share the development of the industry, the technical common points faced by each product, and the development trend of cutting-edge technologies based on common points.
Background technology: SMD packaging refers to surface mounting technology, that is, inserting a light-emitting diode with pins onto a circuit board or later attaching a patch light-emitting diode to a circuit board through an SMT machine, turning it into a concave and convex display carrier. This technology is called SMD packaging. Therefore, according to the three primary colors of red, green and blue, it is divided into: single red for displaying subtitles, dual colors (red and green) for displaying subtitles and graphics, and full color for displaying dynamic images (referring to the three primary colors). In the past nearly 20 years, SMD packaging has evolved from traditional single red and dual colors to full colors, from the mainstream large spacing, long distance, waterproof and high temperature resistant outdoor to high-definition indoor small spacing, from the 20mm spacing of P20 to the current 0.4mm spacing of P0.4. It can be seen that the clarity is getting higher and higher, and the technology is gradually becoming mature and stable. However, there are always difficult points behind the formation of technology: for example, with the demand for smaller and smaller spacing, it is extremely easy to drop the lamp beads during installation and use. In addition, the high heat generated by the LED itself makes the chip and lamp bead machine easily damaged. Therefore, all SMD packaged LEDs have the "caterpillar" phenomenon, that is, a row or a column of lamp beads are damaged, and high-frequency after-sales work is commonplace. In addition, the brightness is too high, and the wick has not been blanked by blue light, so it is very harmful to the human eye during long-term use and is very easy to cause visual fatigue. Screen cleaning is also a common thing during use. Once the screen contacts water, it is particularly easy to short-circuit or get damp, which increases the safety risks of screen use. For this reason, based on these pain points, Xida took the lead in proposing the concept of COB packaging, and was also the first to launch COB series products, solving the problems of traditional display such as waterproof, moisture-proof, bump-proof, dust-proof, corrosion-proof, blue light-proof, salt spray-proof, and anti-static. So what is the principle of such a good advantage? Today, as an industry veteran, I will share with you the technical principle: COB's full name is chip-on-board, which can be translated as chip packaging technology on board. It directly solders the LED chip on the PCB board, and then uses epoxy resin for packaging and curing. Compared with SMD surface mount packaging, COB packaging technology does not require reflow soldering, and directly fixes the IC chip on the PCB board, solders the wires, tests, and dispenses the glue to become a finished product, which reduces many SMD packaging processes, greatly saves process and cost, and at the same time, the stability of the lamp beads is better, so it is not easy to fall off. The biggest difference between this and GOB is that GOB directly attaches a layer of resin material to the SMD for curing. Technical advantages of COB packaging:
Advantage 1: The lamp beads are more stable and not easy to drop. This is related to COB packaging technology and is also its biggest advantage. Due to the influence of conventional SMD packaging, the current small-pitch LED display screen has a high rate of lamp drop. During installation and later use, the lamp beads may drop or not light up, which greatly increases the probability of after-sales. COB packaging greatly increases the stability of the lamp beads, which significantly reduces the rate of lamp drop.
Advantage 2: Anti-collision and pressure resistance. Since COB directly encapsulates the LED chip in the lamp position of the PCB board and then cures it with epoxy resin, the entire lamp forms a spherical surface, which is smooth and hard, and has stronger protection.
Advantage 3: Smaller pitch. Due to the limitations of SMD packaging technology, the minimum pitch of LEDs encapsulated with SMD surface mount technology can only be P0.9, and there is a high phenomenon of lamp drop. After adopting COB packaging technology, the minimum dot pitch can be P0.6, and the stability is good. Of course, COB packaging technology is not without advantages. For example, it requires a high one-time pass rate. Only when there are no problems with the lamp can the glue be sealed. This is a great challenge for the technology. At the same time, it is more complicated to repair and is easy to affect the lamp beads next to it.
In general, COB packaging technology will be a mainstream LED packaging technology in the future. It will form two levels with SMD surface mount packaging. Both have their own advantages. We suggest that if the user has high requirements for the fine display of the screen and wants to use products with higher resolution and smaller dot pitch, then it is better to use COB small pitch display screen, and if it is a screen above P1.8, SMD packaging is more cost-effective. Analyze the application prospects of COB from the perspective of market development: COB is a technological change in the LED industry. COB products can make up for some defects of SMD LED products, have stronger adaptability to the environment, and will be widely used in various scenarios and environments.