The most popular concepts in the LED display industry are mini led and micro led. In particular, the release of Riad P0.4 micro LED products in July almost marked the beginning of the era of “liquid crystal PPI” standard for LED display. LED display has become a direct display technology category that can meet the mainstream demand from medium screen to large screen display, and the product size line covers the longest.

The maturity of ultra-fine spacing LED display products represents the core direction of the future industry. However, while praising the technological progress of “spacing index” and “massive transfer”, the breakthrough in another key direction has not received due attention. This is the problem of LED matrix “substrate” in the era of super spacing: the curtain of upgrading from PCB to glass substrate has also been opened in 2020.

Starting from the new demand of LCD backlight

Although Mini LED can be widely used in independent display products, the industry believes that “liquid crystal backlight” is the first “scale market” of mini LED technology: on the one hand, the new HDR effect standard is almost perfect for mini led, on the other hand, higher PPI will inevitably require the support of Mini LED technology.

That is, whether the 4K of notebook and PC screens, the 8K of TV products, or the ultra-high definition commercial display demand of virtual reality and special display applications in the 5g era, the “PPI” of large, medium and small LCD screens is getting higher and higher. Higher PPI must correspond to: 1. Lower LCD opening rate and more efficient backlight brightness requirements; 2. Finer detail display and finer backlight adjustment requirements; 3. Lightness requirements of high-end products.

For LCD, which needs the support of backlight system, none of the above three requirements points to a common technology, namely Mini led. Mini LED can provide more LED light-emitting crystal welding quantity per unit area, and then continuously upgrade in brightness and adjustable fineness, which is more in line with the needs of 4K / 8K ultra-high definition and HDR effect.

At the same time, for the demand of ultra-thin product design, the previously widely used technology choice was “side type” backlight. However, the “side” backlight is a “low effect choice” in terms of any display effect index – this ultra-thin design essentially sacrifices the image quality. Mini LED technology, with smaller volume of each LED particle and smaller packaging and welding structure, is obviously more suitable for “straight down” ultra-thin design.

However, in the design to meet the further upgrading of mini LED backlight, mini LED technology brings “higher heat intensity” and higher demand for product heat dissipation. The traditional LED display and backlight adopt PCB substrate, which has limitations in heat dissipation performance and can not be infinitely ultra-thin – especially in the face of large-size LED single screen or liquid crystal backlight display, the thermal deformation of ultra thinned PC B “has” formed an unprecedented contradiction “with the miniaturization of LED crystal itself and its integration process.

Therefore, looking for a new “driving backplane” for mini LED has become the key to maintain the optimal product technical characteristics in terms of heat dissipation, stability, ultra-thin integration and high-density integrated control. At this time, the glass substrate is grandly launched – because the core material of the glass substrate and the LED crystal are inorganic semiconductor crystals, which are closer in thermal effect deformation coefficient The ultra-thin strength and heat dissipation capacity of the glass itself are also stronger. At the same time, practice has proved that the glass substrate is also more friendly to the massive transfer technology. Therefore, the application of “glass substrate” on mini led and micro LED has become a “new direction”.

The industry aims at glass substrates and introduces new products

Recently, Guoxing Mini cog program was officially unveiled. According to Guoxing optoelectronics, the mini cob scheme has the characteristics of super large-size integrated packaging, primary optical small od thin design, curved surface packaging and so on. It is more technical and applicable in ultra multi partition display. At present, this technology is mainly used as a high-end LCD backlight product. In the future, it is eager to connect micro led, which can directly replace large-size OLED and LCD panel and become the mainstream technology of the next generation of display.

At the same time, mini cog, as a technical scheme with glass as the substrate, is already a “second generation” product: the early glass substrate manufacturing process adopts the traditional patch process, which needs the help of metal mask process, which not only has high cost, but also aggravates the risk of defect rate. Based on the new chip transfer patch and packaging technology, mini cog not only maintains the advantages of good heat dissipation, excellent cost and high brightness of glass substrate, but also has the advantages of high efficiency and good consistency.

Coincidentally, VOG optoelectronics also announced recently that it has developed a double-sided and single-layer processing technology for new LED drive plate materials such as ceramic and glass substrates, aiming at the problems of many mini led processes and low yield. Through laser drilling (50um), PVD copper film deposition on side a, PVD copper film deposition on side B and yellow light etching circuit, the double-sided film resistance is less than 0.1 ohm, which makes the process route of mini led simpler, higher yield and lower resistance. At present, VOG photoelectric Mini led glass substrate sample has passed the test of well-known domestic panel manufacturers.

On the glass substrate Mini led, domestic panel giants are “faster”: TCL Huaxing has released its first display product mled Xingyao screen, which uses TFT-LCD process combined with amorphous silicon glass substrate to drive active Mini led, in August 2019. TCL Huaxing said that compared with traditional PCB substrates, glass substrate technology is more energy-saving, lower cost, and can achieve the same display effect. BOE, another large LCD panel manufacturer in China, was also on the interactive easy platform at the beginning of the year. The Secretary disclosed that “the company plans to mass produce glass based Mini LED backlight and mini LED production line products in the second half of 2020.”

this is not the only one! In 2020, “glass substrate led” technology is no longer a “feasible technical route research”, but enters the “product stage”, which is only one step away from the real trend of “marketization”. In the PC, Nb and TV markets, the new mini LED backlight for LCD has no “more route options” other than PCB and glass substrate. This almost determines that the glass substrate LED products will inevitably grow on a “large scale” in the future.

Glass substrate: the next focus of LED display

Glass substrate technology changes the future of LED and liquid crystal display

If we only regard the glass substrate as a technical choice of mini LED backlight, we underestimate this new technological progress and breakthrough. In fact, glass substrate LED technology is just a “variable” to change the relationship between “LED display and LCD display”.

In the early days, LED display focused on “large screen”, while LCD display only focused on the market below 100 inches. The two have no intersection of terminal product forms, or the intersection is limited (limited intersection competition on the large LCD splicing screen). At the same time, as the backlight of LCD, LED has also obtained a large market scale, showing a cooperative relationship in the “upstream and midstream” industrial chain.

However, with the development of mini LED technology and micro led, the resolution performance of LED independent display products is improving day by day, which shows alternative advantages in liquid crystal splicing products. With micro led entering the P0.4 spacing era newly released by lyad, it also presents a certain market substitution and competitive advantage with special needs in the mainstream market of 50-100 inch LCD. Combined with the application of mini led in high-end and 8K LCD, LED display and LCD technology have entered the comprehensive competition and cooperation stage of “middle end and middle and upstream industrial chain”.

In the future, once the glass substrate Mini LED backlight and micro led independent display centered on high PPI, ultra-low pixel spacing and high-efficiency ultra-thin design enter the market stage, LED product integration will depend on the core technology of liquid crystal display: TFT glass substrate. The relationship between LED and LCD will be further chelated and become a relationship between you and me. The competitive relationship between LCD panel enterprises, backlight enterprises, complete machine enterprises, middle and upper reaches enterprises of LED display screen and large terminal screen enterprises will also change. The market structure of the whole industry will have relative independence from the three plates of “LED display, LED backlight and liquid crystal display”, and further change to “complex hybrid”. At the same time, glass substrate LED technology will also become an important digestion port of liquid crystal TFT glass substrate, significantly changing the matching relationship between upstream and downstream supply and demand of the industry.

In other words, the glass substrate LED technology will bring the reconstruction of the “industrial chain” from liquid crystal display to LED display and from upstream to terminal, and become “another major innovation” to change the display industry pattern in addition to mini LED / micro led.

Glass substrate LED: better performance and lower cost

“Ultra thin, heat dissipation and high-density drive” is the most widely mentioned advantage of glass substrate at present. However, this is not the whole advantage of glass substrate.

From the perspective of micro LED technology, the pixel spacing in the future is already below P1, or even below p0.5. At the same time, the size of micro LED crystal particles will advance from 100 microns to 10 microns. In this trend, the manufacturing of fine large-area PCB products is becoming more and more difficult and the cost is becoming higher and higher.

Although the fineness of PCB driver board can reach the “extremely high level” of computer CPU or memory module and other products, for display applications (whether independent LED large screen or LED backlight), its biggest feature is to “use ultra-fine and larger area” PCB board—— Historically, ultra-fine PCBs are small plates of high price products, while micro LEDs need large-area plates with cost advantages. This demand difference determines the “application bottleneck” of PCB under the continuous progress of micro led and other technologies in the future.

In contrast to the glass substrate process, ultra-fine TFT driving structure can be obtained in a large area by using semiconductor, lithography and advanced copper process. For example, the size of mature LCD generation 10.5 glass substrate is 3370mm × 2940mm。 TFT driving structure with pixel spacing less than 0.3mm can be formed on such a large substrate at one time. It can be said that such mature and mass production technology is “more than enough” to meet the backplane requirements of mini led and micro LED applications.

At the same time, after decades of development, the equipment and process of TFT glass substrate have long been mature. Even, with the rise of OLED, a number of second-hand product lines can be purchased, and its market supply capacity and scale are far more than “ultra-fine PCB” boards. Even the mature 6th generation TFT glass substrate 15 years ago can meet the “structural unit application size requirements of micro led splicing large screen”.

Therefore, compared with the two compartments, although the glass substrate LED is a new process route, it is a “highly mature upstream” product – at least more mature than the PCB board in ultra-fine and ultra-large board cards, and has the advantages of scale cost and process cost. Moreover, if the massive transfer technology is applied, the friendliness of the glass substrate is also higher – the flatness of PCB will be a big bottleneck for the transfer of micro LEDs below 50 microns, but the glass substrate does not have this problem. According to media reports, when the LED grain size of Sony less than 30um was moved to the PCB, it must be transferred to a temporary substrate before it can be transferred to the PCB again.

To sum up, glass substrate LED is likely to be the “perfect match” for the continuous progress of mini led and micro LED technology: ultra micro LED crystal, cob and flip chip, huge transfer, TFT of glass substrate, etc. are expected to form the “four beams and eight buildings” for the progress of the next generation of LED independent display and the new generation of LCD backlight products, bringing an unimaginable new realm to the ultimate performance of human display industry.

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