As we all know this is a need to overturn the traditional process, involving industry fields of disruptive innovation technology, the technology for domain experts are not easy to break through the bottleneck.
Taiwan institute and the three factory last year cooperative development of passive matrix driving super small spacing of Micro LED display
module, success will be Micro LED chip array directly transferred to the PCB substrate, only RGB full-color singularly lacking red light.
After some efforts, finally this year is to get red 'bright' phase.
Red sleek and rate than blue, green, weaken the structure problem is different from the previous 6 cm x 6 cm of Micro LED display module, spacing (
Less than 800 microns, 80 x 80 pixel resolution, the new module size is 6 cm x 10 cm, spacing of about 700 microns below, 96 x 160 pixel resolution, the LED chip size is the same within 100 microns.
Transfer process from the front to the back end, Taiwan institute lightning the intelligent application of micro system group deputy team leader Dr Fang Yanxiang mentioned two big technical problems, one is red chip utilization rate and yield is insufficient, the other is the structure of 'weakening'.
2018 exhibited by the ultra Micro small spacing alone the lack of red light, LED display module spacing is less than 800 microns, the resolution of 80 x 80 pixel2019 new Micro success RGB LED display module, distance of about 700 microns below, 96 x 160 pixel resolution 'to chip utilization and yield, red light or a problem,' Fang Yanxiang with 4 inches LED wafer as an example, points out that the wafer after deducting 2 mm outside diameter, the available area of yield under a single standard or permission of 99%, which is looking at wavelength (
And the driving voltage (
Or reverse leakage (
But if three numerical standard to have both, and the overall yield is likely to be less than 60%, especially the red light is limited by material and features, perhaps even may not be able to achieve 50% yield.
Look at the available area yield is not enough light, Fang Yanxiang said, Micro LED process under the area of the need to transfer to define yield.
In simple terms, assuming that huge amount transfer module transfer area is 6 cm x 3 cm, it said in the rectangular area (
In Micro LED chip array must comply with the foregoing three yield standard, cannot have bad point to transfer, that is to say the entire wafer may comply with all standards, only a specific blocks can yield unstable lead to transfer of less area, also the efficiency of whole fell sharply.
In the industry's top technology, wafer chip to achieve high evenness are also has the very big space.
Red light is limited by material and characteristics of yield are lower than those of blue light, green relative Micro LED red sleek and rate need to be improved, not only has the weakening of the structure of the Micro LED is more difficult to find.
Weaken the structure is a key of success for huge amount transfer.
Fang Yanxiang shows that Micro LED chip in the process must follow the material such as silicon or glass substrate joint temporarily, again through the laser stripping (
激光提升- - - - - -
Remove the sapphire substrate, and then in the form of flip chip will originally LED structure turn, face down, and make the p-type and n-type electrode production on the same side, for Micro LED miniature to micron level and more difficult.
To make Micro LED in the process of transfer huge amount absorb, can smoothly from substrate and temporarily not fragment, so have to make hollow type weakening of the structure, at the bottom of the LED is in less than 1 mu m micron level pillar support.
When transfer module learned LED upward, as long as the Micro disconnect pillars can be LED out of the temporary base board, then move down to the TFT or PCB board, but this process also test whether the LED itself is not strong enough, when under pressure can still keep in good condition, and red than blue and green light are relatively fragile, roughness and PCB (
Large, up and down height difference is more than 200 microns, slightly improper pressure transfer success rate can reduce the red light.
As for the glass substrate is because there is no PCB roughness is big, Micro LED transfer difficulty is relatively low.
Last stage engineering institute has exhibited a 6 cm x 6 cm, distance of about 750 microns, 80 x 80 pixel resolution of Micro LED display module, transparent is ultra-thin glass, adopted by the RGB trichromatic is implemented on technology;
This year, made the new Micro transparent LED display module, size 4.
8 cm x 4。
8 cm, distance of about 375 microns, 120 x 120 pixel resolution, obviously a display effect more careful than before.
2018 Micro transparent LED display module, distance of about 750 microns, 80 x 80 resolution pixel2019 edition of Micro transparent LED display module, distance of about 375 microns, 120 x 120 pixel resolution, focusing on three major applications: e-sports, AR, transparent displays Micro LED screen has high brightness, high efficiency and low power consumption, high resolution color saturation, long life and other characteristics, e-sports screen (in
, augmented reality (
, transparent displays, and other areas of the application, can play more advantages than the OLED and LCD, and the three application is also Taiwan industry research institute is also actively develop the most promising direction.
E-sports screen used to view, Fang Yanxiang mentioned mm light-emitting diode (although already on the market at present time
Technology, but it is always as display backlighting, Micro LED can directly as a pixel display back light is not required.
Compared with the Mini LED or same as spontaneous light OLED display technology, Micro LED contrast even more pure, the color performance is also better, in the key refresh rate on the performance is better than that of the OLED, and no brand or recession, in the high-end consumer market in the future development potential is very period.
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