Fine Pitch LED Display: A Complete Guide to Sizes, Advancements & Packaging

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With the continuous development and improvement of LED technology, indoor LED displays, especially fine pitch products, meet market demand and save energy with their seamless splicing, low brightness and high gray, high refresh rate, ultra-high definition, low energy consumption, long life, etc. The characteristics of economic development advantages have been widely used in: electric power production dispatching control center, military command and control center, urban management emergency command center, traffic management command center, industrial process control display system, radio and television display and monitoring system, shopping malls, hotels, Communication information display system, financial securities information display system, government enterprise multimedia video conference display system, mining safety production monitoring system, urban environment monitoring and command system, fire protection, meteorology, maritime flood control command system, airport and subway flight display, safety monitoring system, etc. wide range of areas.

Fine pitch LED display

What is Fine pitch LED display

In fact, in essence, Micro LED and Mini LED are both based on tiny LED crystal particles as pixel light-emitting points. The difference is that Micro LED uses 1-10 micron LED crystals to achieve 0.05 mm or smaller. A display with pixel particles of 0.5-1.2 mm size; MiniLED uses LED crystals of tens of microns to achieve a display with pixel particles of 0.5-1.2 mm. The gine pitch LEDs we are familiar with use sub-millimeter LED crystals, ultimately achieving a 1.0-2.0 mm pixel particle display.

First of all, considering only the size, there is overlap between the definitions of various sizes. The reason why it is called small spacing is compared with large spacing. The development of LED displays is a gradual process. When blue light-emitting diodes appeared, full-color LED displays appeared. However, early full-color LED displays were mainly used for outdoor displays, and their spacing even exceeded 1 cm. As the size of semiconductors and light-emitting diodes shrinks, the spacing of full-color LED displays also shrinks. At present, full-color screens with a pitch of less than 5mm and greater than 1mm are generally called small pitches.

Mini LED is as the LED point spacing continues to shrink. When lamp beads smaller than 1mm appear, the concept of Mini LED appears. In fact, after the millimeter, there are the dmm (10 silica meters = 1 millimeter), the centimeters cmm (10 silica meters = 1 silica meter), and then the micron (10 microns = 1 millimeter). However, the two units of silk meter and lumen meter are no longer used, but this size range is obviously not microscopic. However, considering the relationship between the size of the lamp beads and the pixel pitch, this will also range from 1.5mm to 0.3mm. Defined as Mini.

MicroLED, in fact, Micro here means smaller and does not refer to the specific size. At present, the legal measurement unit of length we use generally still uses millimeters when it is less than 1 mm, such as 0.01mm, but when it is less than 0.01mm, microns are often used, that is, 0.01mm=10um. Of course, it is also correct to directly write 0.1mm as 100um, which is just like writing 1cm as 10000um. This is also the reason for the current confusion about the definition of Micro LED size.

Secondly, it is because each manufacturer defines it according to the characteristics of its own products. Confusion is even more likely to arise when production processes and spacing are combined. This is because each production process has overlapping pitches.

Evolution and Growth of Fine Pitch LED Display Technology

Since 2015, the fine-pitch market has exploded in growth, with significant advantages in brightness, color, reliability, etc., and the rapid replacement of LCD and DLP splicing screens in the professional display market. The current penetration rate is close to 20%, driven by technological progress and cost reduction. The cost performance of fine pitch continues to improve, and there is huge room for substitution. From an average of 10mm to less than 2mm, it will begin to compete with DLP and LCD screens in the indoor display market.

In terms of global market size, according to data from OFweek Industry Research Institute, it is expected to approach US$1.8 billion in 2020. From the perspective of product pixel pitch, more than 70% of products have a pixel pitch between P2.5-P1.7; from the perspective of regional distribution, the largest region is the Asia-Pacific region (50-60%), followed by North America and Europe. In terms of regional distribution, the Asia-Pacific region accounts for about 50% to 60% of the market with the highest proportion, followed by North America and Europe. In terms of application fields, gine pitch LEDs are mainly used in many industries such as commercial displays, high-end retail, movies, advertising, entertainment, etc. However, gine pitch LEDs still have their physical technical limitations, so for the consumer application market with smaller spacing , leaving it to Mini LED and Micro LED.

As a transitional application between gine pitch LED and Micro LED, the advantage of Mini LED is that Mini LED backlight can make use of the existing LCD technology foundation (using local dimming design, thousands or tens of thousands of direct backlight sources, and has a more refined HDR Partitioning) combined with mature RGB LED technology shortens the product launch cycle. It solves the problem that ultra-fine-pitch LED displays are easily damaged and makes up for the shortcomings of gine pitch LEDs. In terms of production, although Mini LED is currently in the mid-term stage, the difficulties it faces are not as difficult to break through as Micro LED. However, smooth promotion still requires joint efforts from epitaxial wafers, wafers, packages, substrates, TFT backplanes, driver ICs and equipment manufacturers. According to relevant reports, the possible future development directions of Mini LED include TVs, mobile phones, automotive panels, monitors, e-sports notebooks, etc. It is estimated that the overall Mini LED output value will reach 1 billion US dollars in 2023, including LED display screens and large-size TVs, etc., will be the mainstream application of Mini LED.

In the competition of small pitch packaging technology, who will become the mainstream?

The LED display industry has widely transitioned to the surface mount (SMD) process after the direct insertion (Lamp) process. As the surface mount (SMD) form becomes popular and is about to replace the direct insertion, COB packaging has emerged. , which is quite similar to the surface mount (SMD) package. In fact, comparing COB with SMT is a bit of a "Guan Gong vs. Qin Qiong", which is wrong - the "Surface Mount" process of gine pitch LED screens and COB are not actually in a "direct competition" relationship. COB is a packaging technology, while surface mounting is a structural layout and electrical connection technology for a large number of tiny devices. They are at different stages of the electronics industry, especially the LED industry. In other words, surface mounting is the core process of LED screen manufacturers, while packaging technologies such as COB are the "work" of the "LED packaging industry", the upstream enterprise of terminal manufacturers. There is no need to directly compare which one is better between the two, but they cannot withstand the current boom in LED gine pitch displays. In order to achieve the best solution for LED gine pitch displays, everyone is crossing the sea and showing off their magical powers.

In the competition of gine pitch manufacturing processes, many gine pitch manufacturers can only passively work hard on the reflow soldering surface mount process and other aspects. However, as the spacing continues to develop, the number of LED lamp beads required to be mounted per unit area has doubled geometrically, which has placed higher and higher requirements on the surface mounting process. Affected by the smaller spacing of small spacing and the greater difficulty of this dense mounting process, while the spacing of small spacing LED displays continues to decrease, the problem of high dead light rate has not been effectively solved. Some manufacturers, represented by Sony, have begun to explore and try to solve this problem from the source, that is, considering dense arrangement solutions from the chip design and packaging stages.

Like flip chip packaging, COB also uses the form of direct packaging of bare cores. COB stands for chip-on-board. In this technology, the LED bare chip is adhered to the PCB substrate with conductive or non-conductive silver glue, and then wire bonded to achieve its electrical connection.

Compared with traditional SMD LED packaging, COB packaging has certain advantages in terms of manufacturing efficiency, low thermal resistance, light quality, application, cost, etc. The production process of COB packaging is basically the same as that of traditional SMD. The efficiency of COB packaging is basically the same as that of SMD packaging in terms of die bonding and wire bonding processes. However, in terms of dispensing, separation, spectroscopy, and packaging, COB packaging is more efficient than SMD. The product is much higher. Traditional SMD packaging labor and manufacturing costs account for about 15% of the material cost, and COB packaging labor and manufacturing costs account for about 10% of the material cost. Using COB packaging, labor and manufacturing costs can be saved by 5%.

The system thermal resistance of traditional SMD packaging applications is: chip-die die glue-solder joint-solder paste-copper foil-insulation layer-aluminum material. The system thermal resistance of COB packaging is: chip-die die glue-aluminum material. The system thermal resistance of COB packaging is much lower than that of traditional SMD packaging, so it can greatly increase the life of LEDs.

Traditional SMD packaging attaches multiple discrete devices to the PCB in the form of patches to form light source components for LED applications. This approach has problems with spot light, glare and ghosting. The COB package is an integrated package and a surface light source. It has a large viewing angle and is easy to adjust, reducing the loss of light refraction. Based on the characteristics of low thermal resistance, high luminous flux density, less glare, and uniform light emission, COB light sources have been widely used in the LED lighting industry in recent years. Since COB technology has so many advantages, why has it been stumbling in the LED display industry?

In response to doubts in the market that "COB products are not repairable, will encounter many problems during mass production, and are not as good as SMD for packaging", Liang Qing, general manager of Wei Qiaoshun Optoelectronics, believes that to compare the advantages and disadvantages of a technology, we must start from the industrial chain. The source extends all the way to the end, instead of just looking at a certain technical link, everything must be comprehensively analyzed and evaluated based on the terminal application.

COB packaging and SMD packaging are on the same starting line in the selection of LED chips, and then they chose different technical routes. SMD packaging is a single lamp packaging method, which has advantages over ensuring the quality of a single lamp bead. However, the cost will be relatively high due to too many production processes. It will also increase the cost of transportation, material warehousing and quality control from the lamp bead packaging factory to the screen factory.

In terms of manufacturing gine pitch LED displays, traditional SMD packaging increases the difficulty of patch technology as the product point density increases, and the cost of the product will also increase. Moreover, the higher the point density, the more the cost increases, showing a non-linear relationship of accelerating growth. Especially in the reflow soldering process, the four-corner or hexagonal bracket used in SMD packaging needs to solve the problem of soldering yield of a large number of bracket pins through the reflow soldering process on the lamp bead surface. If SMD is to be applied outdoors, the outdoor protection yield problem of the bracket pins must be solved. gine pitch LEDs using SMD packaging technology are extremely prone to dead or broken lights during use.

In the competition of pitch LED packaging forms, we can regard traditional SMD packaging as the first-generation packaging, COB as the second-generation packaging technology, and Micro LED technology represented by CLEDIS represented by Sony represents the gine pitch packaging technology. The latest developments in spacing. As for who can win in the competition, it depends on the advancement of technology and market acceptance. At present, SMD packaging undoubtedly occupies the mainstream of the market, but in the future, with the growth of COB and Micro LED technology, the gine pitch LED display market will become increasingly differentiated. Will the east wind (SMD) overwhelm the west wind (COB, Micro LED), or will the west wind overwhelm the east wind? We'll see.

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