Flip-chip technology makes LED display “touchable”
Date: 2019-12-12
As a kind of display product with high engineering and customizability, LED display screens appeared in the vicinity of landmark buildings such as the surface of the building and the square as a large outdoor screen at the beginning of its birth. From PXX to PX, and then break through P1, and continue to march toward P0.X, LED display products have begun to penetrate into the direction of indoor applications, and the sense of "distance" between the early outdoor large-screen era and users is following The gap is constantly falling and getting closer. Whether Samsung enters the LED movie screen or the mutual achievements between the construction of e-sports venues and LED display manufacturers, this is all explained. Therefore, the controversy over whether "developing smaller-pitch LED display products is of practical significance" was clearly settled: For LED display manufacturers, the dot pitch is getting smaller and smaller, which is because LED displays can penetrate the indoor market and expand The foundation of more subdivided fields, and on the eve of the era of "5G + 8K", the interactivity of LED displays is only possible when the dot pitch is getting smaller and smaller. The development and maturity of the small-pitch technology has shortened the distance between the LED display and the audience. When the screens of LED display products start to become more and more clear, how to further reduce the distance with the user, so that the LED display and the User interaction has become an issue that manufacturers must consider.
Although LED display has the advantages of fast response speed and high size freedom compared to other display methods, in terms of touch screen technology, the difficulty of LED display to achieve touch interaction is significantly higher than other technologies: LED display wants to achieve For interaction, it is necessary to reduce the dot pitch as much as possible, so that even when the picture is viewed at a close distance, there is still no obvious "graininess", but as the dot pitch is reduced, it will inevitably face the stability brought by the reduction of the solder foot. With regard to safety issues, for LED displays, as a discrete component assembly product, LED display products have a "congenital deficiency" in stability compared to other display products. Even bumps during transportation may cause the screen body. The display of the display is faulty, so at this stage, many LED display screens often make a "No Touch" mark during exhibition and use. This is because the audience can easily sweat and grease secreted from their fingers when touching. Remaining on the screen, causing hidden dangers of short circuit and reducing the life of the lamp beads, and the static electricity carried by the human body can cause electrostatic breakdown. . Therefore, it is conceivable that the touch caused by the audience's touch interaction is obviously stronger and more frequent than the collision during transportation. In terms of touch screen, the pace of LED display is always slower than other display methods. Although some manufacturers choose to solve the above problems by laminating the screen surface, in general, how to solve a series of problems such as dead lights, bad lights, short circuits, and electrostatic breakdown caused by touch, LED display companies have a long way to go.
However, with the advent of the "5G + 8K" era, ultra-high-definition video display and ultra-high-speed signal transmission will inevitably put forward higher technical requirements for display products, and this will also necessarily include increased requirements for touchability. If you want to make the display screen “at your fingertips”, the first thing to consider is how to improve the stability and security of the screen.
At present, the types of LED packages in the market are different. The N in 1 SMD (4 in 1/6 in 1) products that often appear in Z are an extension of the SMD technology line and a transition product of traditional SMD production plants. The SMT technology is still used for placement. 4 in 1 lamp beads are used. The distance between the edge of the lamp beads and the internal solder joints is about 0.1mm. The core issues such as the air tightness of the lamp bead edges and bare solder pins are not completely solved. Product reliability The problem will be exposed again in the process of delivery and has not been effectively improved. Under normal conditions, a gap of 0.25mm needs to be reserved between the lamp beads, and the discrete device size specifications, basically can not achieve the bulk supply below 0.9mm. At the same time, N in 1 products are more grainy in the display effect, and the discrete pits are serious in the side viewing angle.
Therefore, in the current dressing technology, which has reached the point that "the fish and the bear's paw cannot have both." Because of the dilemma between size and stability, which is close to the small size ceiling, some manufacturers have begun to find alternatives and adopt flip-chip mounting. Technology for packaging. Because the flip chip technology directly bonds the light emitting chip to the pad of the PCB board, and uses a wireless packaging process, the soldering area is from point to surface, which increases the soldering area and reduces the soldering points, so the product performance can be improved. more stable. As an upgraded product of front-mounted COB, flip-chip COB further improves reliability based on the advantages of ultra-small dot pitch, high reliability, and non-glare area light source of front-mounted COB. The packaging layer has no bonding wire space, and the packaging layer is thinner and lighter, reducing heat Resistance, improve light quality, and improve display life. Ultra-high protection, anti-collision, shock-proof, waterproof, dust-proof, smoke-proof, anti-static. More importantly, because it inherits the characteristics of the overall COB package, it has a high degree of guarantee in touch smoothness, and does not have a bumpy feel when touched, and can also withstand high-intensity and frequency touch operations. , There is no need to worry about the situation where the lamp beads are damaged by excessive force during the touching process.
It can be said that flip-chip COB is a true chip-level package, because it does not need to be wired, and the physical space size is limited only by the size of the light-emitting chip. ability. Therefore, compared to SMD and other packaging forms, flip-chip COBs have the above characteristics, and before the advent of the "zero-interaction interaction of human screens" era, they have the advantage of other packaging methods on the road to touch screen development. It should be noted that as the advantages of flip-chip technology become more and more obvious, some SMD manufacturers have also begun to use flip-chip technology for packaging. However, due to cost considerations, the number of companies choosing flip-chip SMD is still less than that of flip-chip. COB enterprises.
However, while affirming the advantages and progress of flip-chip COB, we must also note that there will not be perfect technology in this world. No matter what kind of flip-chip technology, the threshold increase brought by technological upgrading, and the front-end equipment upgrade The cost increase is a problem that must be faced by manufacturers choosing flip-chip technology, especially the flip-chip COB technology, which has a higher dependence on the machine, so the operational risks brought by the upgrade of the machine. It is also a risk that every business needs to face when making a choice. While Flip COB has made progress on the basis of COB, it also inherits the shortcomings of the COB that cannot be repaired by a single lamp and the uneven color of the ink. Compared with other packaging methods, COB mounting still has many advantages, so it is conceivable that with the continuous decrease of the dot pitch, the flip-chip COB technology is becoming more mature and commercialized. The arrival will undoubtedly become a tangible possibility, not just a theoretical assumption.
English
Follow us