(3) The development history of LED screen display technology
Looking back at the development history of LEDs, the development of traditional LEDs has a gradual feature, that is, most brands in the market are gradually transitioning from outdoor LED displays and large-pitch LEDs to small-pitch products.
Then it enters the small and fine pitch markets below P2.5 pitch, and gradually gains wider applications in the indoor display field. The lamp bead pitch continues to shrink, and the display effect continues to improve.
Small-pitch LED technology has developed rapidly since 2016, and has become the main force of LED display growth at this stage. At present, the LED small-pitch display technology, process and industrial chain supporting facilities are relatively mature.
Cost prices continue to drop, and the vast space for indoor display has been successfully opened. However, there are still physical technical limitations for small-pitch LEDs. Therefore, smaller-pitch Mini/MicroLEDs have begun to come into the eyes of the public.
(4) The development history of LCD display backlight
Traditional LED direct-lit backlight: It is the current mainstream backlight solution for liquid crystal displays. The cost of this solution is low, and dynamic partitioning can be achieved; it is thicker and higher in energy consumption. Traditional LED edge-lit backlight: It can be thinner and has no dynamic partitioning.
Quantum dot backlight: A wide color gamut can be achieved, but the production cost is relatively high, it is slightly toxic, and the cost is relatively high. Only a few manufacturers have mass production capabilities.
Mini LED backlight: Using direct backlighting, the traditional LED die size is reduced to between 100 200 μm, which greatly increases the number of backlight sources. With local dimming control, it can achieve regional brightness adjustment and bring a better visual experience.
This solution has the characteristics of energy saving, light and thin, wide color gamut, ultra-high contrast, fine dynamic partition, etc., which can overcome the shortcomings of other backlight methods, but the current production cost is relatively high, and it is mainly used for high-end displays.
(5) Micro LED technology needs a breakthrough
At present, there are three main technical bottlenecks restricting Micro LED: one is mass transfer, that is, how to transfer Micro LED chips to TFT circuit substrates in batches.
And according to the micron-level cycle assembly to form a high-density two-dimensional array structure, the second is the problem of the pixel light source of the three-primary-color Micro LED; the third is the packaging of the Micro LED.
Due to the limited micronization of the pixel assembly size of the three primary color Micro LED, it is difficult to achieve ultra-high-density packaging. How to miniaturize LEDs requires a wafer-level process level.
For example, a 4K level Micro LED screen requires more than 8 million LEDs to be highly integrated, so theoretically it is extremely difficult to apply it to a large-size screen.
At present, the industry generally believes that massive transfer is the biggest obstacle facing the Micro LED production process. How to integrate yield and efficiency and transfer tens of thousands of LED chips to TFT substrates is the biggest obstacle facing Micro LED production.
The mass transfer of Micro LED mainly includes two methods: physical transfer and chemical transfer. Among them, the physical transfer method mainly includes the electrostatic adsorption transfer technology represented by LuxVue (acquired by Apple in 2014);
The chemical transfer method mainly includes micro-transfer printing technology (μTP technology) represented by X-Celeprint.
(6) Mini LED technology needs to be broken through
Mini LED mass production technology still has difficulties, and urgent efforts are needed to accelerate industrialization. Although Mini LED displays have achieved small-scale commercial shipments, there are still a few bottlenecks in large-scale mass production that need to be further resolved.
The first is chip manufacturing. The mass production of Mini LED chips requires sub-micron accuracy, and the current laboratory process accuracy is only 10 microns;
The second is the problem of massive transfer. Mass production requires that the transfer dead pixel rate is less than one part per million, but currently it only reaches one part in 100,000, and the repair cost is relatively high;
The third is the problem of electrode connection. The cost of electrode connection flip-chip technology is too high. At present, only the formal mounting process can be used in China, which reduces product reliability;
The fourth is the driving problem, it is urgent to develop refined PCB backplane manufacturing and TFT backplane driving technology; the fifth is the splicing problem, the existing splicing process can only achieve long-distance visual seamlessness, and the smooth seamless splicing is more difficult .
