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What’s the Difference Between LEDs, Mini LEDs and Micro LEDs
October 22, 2018 Recently, Bob Raikes, CEO of Meko, wrote Display Daily articles on consecutive days addressing the question of how do we define a standard LED, a mini Led and a micro LED. Definitions are always front and center for market researchers as they have to prepare tables with labels. The micro LED market was segment arguably started by Sony when they called their 55” Crystal- LED TV a microLED, which was 100 microns (0.1 mm) along the edge. Samsung used its own definition for the term microLED and said its 'Wall' display had microLEDs, which were around 0.4mm x 0.125. The following image of the Samsung Wall display shows that the LEDs are much bigger than on the Sony Crystal LED. Figure 1: Samsung vs. Sony LED Pitch |
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Source: Meko
The pitch of the display is 0.82mm (calculated from the diagonal and resolution), which effectively shows the LEDs 410μm x 124μm based on the image. They are very different from the Sony pixels. Sony quotes the area of the pixels on its display as having an area of less than 0.003 mm² , which would mean that each side (assuming they are square) is 54 microns. The Samsung LEDs, on the other hand, would be 0.051mm² - some 17 times larger than the Sony device.
Raikes would like to set the lower size of miniLEDs as the upper end of the microLED definition, but says it is less clear where the upper size limit should be. He would like to define the microLED as 'up to 100 micron' per side and with MiniLED as having a maximum side length of 100 microns to 200 microns. Alternatively, he suggests considering the area as a measure rather than side length, which means that a microLED would be smaller than 0.01mm² while a MiniLED would be from 0.01mm² to 0.04mm² of area. LED Inside is using 200 microns as an upper size for MiniLED. It also considers a limit down to 50 microns for the lower limit between MiniLED and microLED. A key difference that is highlighted by Yole is that while MiniLED can be packaged as SMDs or Chip on Board (CoB) devices, MicroLEDs are strictly CoB architecture, where the LED chip is directly connected to the circuit board. Whether we need a size definition of LEDs is not clear, but what is necessary to know how the LEDs are used, either as a light source in backlights and luminaires or as individually addressed sub-pixel emitters in displays. Now we turn to the slimming down of LEDs used in backlights, which enable the transformation of local dimming from large area displays to small/medium displays and the increase in the number of dimming areas. Mini LED-backlit displays should improve quality for images viewed indoors in a short distance with better contrast and color saturation. For the upstream chipmakers, the increasing adoption of the mini LED technology will help them digest their production capacity as mini LED backlights consume more chips than the standard LEDs. Panel makers in Japan, Korea and Taiwan, such as Sony, AUO and Samsung Electronics, have started using mini LED backlights in mass-production process, rolling out products targeting the high-end customized segment. Mini LED pixel pitch has generally been reduced to below 1mm (P1.0). , Digitimes Research estimates that the smallest pitch so far in 2018 has reached P0.75, with the prospects of being reduced to P0.4-0.5 in 2019. Mini RGB LED displays are able to compete with LCD displays in the indoor enterprise display market.
But since mini LED displays also consume more power and carry higher production costs, these products are currently designed for the premium market and the chance for them to make it to the household market remains low at the moment. LED epitaxial wafer and chip maker Epistar has disclosed it has spun off its semiconductor foundry business unit and will also turn its mini LED R&D operation into a separate entity next year. The foundry business has become a wholly-owned subsidiary Epistar Semiconductor since October 1, while the mini LED R&D unit will turn into Yen-Rich Technology, which Epistar will retain full ownership, in January 2019, according to the firm. Epistar Semiconductor focuses on producing VCSEL (vertical-cavity surface-emitting laser) epitaxial wafers and chips as well as GaN-on-Si chips. Due to fast growing demand for wireless data communication from the smartphone and headphone segments, demand for VCSEL chips will be strong in 2019, Epistar said. Epistar Semiconductor currently has monthly production capacity of 2,000 4-inch VCSEL epitaxial wafers and will expand the capacity to 3,000-4,000 in third-quarter 2019. It is also setting up monthly production capacity of 2,000 6-inch VCSEL epitaxial wafers, with production to start in first-quarter 2019 and plans to further expand it 5,000-6,000 wafers. Epistar said it originally shipped mini LED chips to clients but found that many system vendors actually needed mini LED modules integrating chips with PCBs. This is motivating Epistar to set up Yen-Rich, with the subsidiary to handle R&D and build a supply chain for mini LED modules. But Epistar said Yen-Rich would undertake small-volume trial production for modules, with volume production to be outsourced to LED packaging service provider ProLight Opto Technology, of which Epistar is the largest shareholder. Epistar said it has begun small-volume production of mini LED chips for backlighting 27-inch gaming LCD monitors and over 100-inch LCD displays. Epistar newly developed 400-micron mini LEDs for use in RGB fine-pitch displays are being validated by clients. The company is making efforts to improve the yield rates, and expects to begin volume production for clients using them in indoor and outdoor displays in first-quarter 2019. Epistar is also developing 250-micron mini LEDs, with production likely to begin in one year. Demand for mini LEDs is could take off in 2019, particularly for those used in backlighting applications, Epistar noted, adding mini LEDs will take up 5-10% of its production capacity for blue-light LEDs in 2019 and the proportion will rise to about 30% in 2020.
Raikes would like to set the lower size of miniLEDs as the upper end of the microLED definition, but says it is less clear where the upper size limit should be. He would like to define the microLED as 'up to 100 micron' per side and with MiniLED as having a maximum side length of 100 microns to 200 microns. Alternatively, he suggests considering the area as a measure rather than side length, which means that a microLED would be smaller than 0.01mm² while a MiniLED would be from 0.01mm² to 0.04mm² of area. LED Inside is using 200 microns as an upper size for MiniLED. It also considers a limit down to 50 microns for the lower limit between MiniLED and microLED. A key difference that is highlighted by Yole is that while MiniLED can be packaged as SMDs or Chip on Board (CoB) devices, MicroLEDs are strictly CoB architecture, where the LED chip is directly connected to the circuit board. Whether we need a size definition of LEDs is not clear, but what is necessary to know how the LEDs are used, either as a light source in backlights and luminaires or as individually addressed sub-pixel emitters in displays. Now we turn to the slimming down of LEDs used in backlights, which enable the transformation of local dimming from large area displays to small/medium displays and the increase in the number of dimming areas. Mini LED-backlit displays should improve quality for images viewed indoors in a short distance with better contrast and color saturation. For the upstream chipmakers, the increasing adoption of the mini LED technology will help them digest their production capacity as mini LED backlights consume more chips than the standard LEDs. Panel makers in Japan, Korea and Taiwan, such as Sony, AUO and Samsung Electronics, have started using mini LED backlights in mass-production process, rolling out products targeting the high-end customized segment. Mini LED pixel pitch has generally been reduced to below 1mm (P1.0). , Digitimes Research estimates that the smallest pitch so far in 2018 has reached P0.75, with the prospects of being reduced to P0.4-0.5 in 2019. Mini RGB LED displays are able to compete with LCD displays in the indoor enterprise display market.
But since mini LED displays also consume more power and carry higher production costs, these products are currently designed for the premium market and the chance for them to make it to the household market remains low at the moment. LED epitaxial wafer and chip maker Epistar has disclosed it has spun off its semiconductor foundry business unit and will also turn its mini LED R&D operation into a separate entity next year. The foundry business has become a wholly-owned subsidiary Epistar Semiconductor since October 1, while the mini LED R&D unit will turn into Yen-Rich Technology, which Epistar will retain full ownership, in January 2019, according to the firm. Epistar Semiconductor focuses on producing VCSEL (vertical-cavity surface-emitting laser) epitaxial wafers and chips as well as GaN-on-Si chips. Due to fast growing demand for wireless data communication from the smartphone and headphone segments, demand for VCSEL chips will be strong in 2019, Epistar said. Epistar Semiconductor currently has monthly production capacity of 2,000 4-inch VCSEL epitaxial wafers and will expand the capacity to 3,000-4,000 in third-quarter 2019. It is also setting up monthly production capacity of 2,000 6-inch VCSEL epitaxial wafers, with production to start in first-quarter 2019 and plans to further expand it 5,000-6,000 wafers. Epistar said it originally shipped mini LED chips to clients but found that many system vendors actually needed mini LED modules integrating chips with PCBs. This is motivating Epistar to set up Yen-Rich, with the subsidiary to handle R&D and build a supply chain for mini LED modules. But Epistar said Yen-Rich would undertake small-volume trial production for modules, with volume production to be outsourced to LED packaging service provider ProLight Opto Technology, of which Epistar is the largest shareholder. Epistar said it has begun small-volume production of mini LED chips for backlighting 27-inch gaming LCD monitors and over 100-inch LCD displays. Epistar newly developed 400-micron mini LEDs for use in RGB fine-pitch displays are being validated by clients. The company is making efforts to improve the yield rates, and expects to begin volume production for clients using them in indoor and outdoor displays in first-quarter 2019. Epistar is also developing 250-micron mini LEDs, with production likely to begin in one year. Demand for mini LEDs is could take off in 2019, particularly for those used in backlighting applications, Epistar noted, adding mini LEDs will take up 5-10% of its production capacity for blue-light LEDs in 2019 and the proportion will rise to about 30% in 2020.
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