Key technical difficulties and directions of Micro LED

Release date: 2018-03-26 Source : arrogant LED network share:

Micro LED skills have been fired and shocked, it is the next generation of the show skills overlord, but also the star of 2018. However, there are still many problems with Micro LEDs. Whether it is process skills, inspection specifications, or production costs, there are great gaps between many commercial applications. One of the most important challenges is how to introduce a lot of production. Decrease its production costs, and this part is called "huge handling."

To understand the huge amount of handling, of course, you must first know what is the Micro LED, and how it differs from the traditional LED. The full name of the Micro LED is "Micro Light Emitting Diode". Chinese is also called a micro-light emitting diode. It can also be written as "μLED".

The biggest difference from the general LED is of course the scale. However, the number of scales is called Micro LED, and there is still no consistent specification, so it is the status of the manufacturer. Take the definition of Taiwan's crystal power as an example. The general LED die is between 200 and 300 micrometers (micrometer, μm), and the Mini LED (called Micro LED precursor) is about 50 to 60 micrometers. The micro LED is in the 15 microns.

1μLED wins all the skills and the mass production is only the battle

Because of the difference in grain size, their respective applications are different. The general LED chip is mainly used for lighting and display backlight module; as for the Mini LED, it will also be used in backlight operation, but it will be in high-end consumer products, perhaps for car shopping malls, such as Innolux's AM The miniLED is used in the appearance of the car; as for the Micro LED, its application concept is completely different from the former two, it will be a new display skill, and its competition policy will be OLED.

From the perspective of skill standards and application concepts, μLED is superior to the current display skills in terms of brightness, response speed, power consumption and longitude. It can almost be said to have the potential to completely replace the appearance of LCD and OLED, but only The problem is its ability to produce capital and mass production.

Now the biggest production challenge of μLED is how to put a huge amount of micron-level LED crystals on the standard substrate or circuit through high-precision equipment, and this program is called mass handling (Mass). Transfer ).

In fact, massive handling is an academic term that is often used in the engineering design of material handling processes that touch the dispersion and convection of matter or particles within a physical system.

In more detail, massive handling is delineating a chemical or physical mechanism. It is a phenomenon of transport, which means that a large number of points (molecules or particles) move from one end to the other. It can be a single phase, perhaps multiple phases, and it can touch a liquid or gas phase, and sometimes it can also occur in solid matter.

A classic example of a large amount of handling is the "transpiration" of water. Through transpiration, many water particles can be moved to another substance. Similarly, the same is true for dispersion.

2 How to carry tens of millions of micron-sized LED chips

For the production of μLED, it is necessary to move millions or even tens of millions of micron-sized LED chips to the circuit substrate correctly and with power. Taking a 4K TV as an example, the number of crystals required to be transported is as high as 24 million (calculated by 4000 x 2000 x RGB three colors). Even if 10,000 pieces are transported at a time, it is required to repeat 2400 times.

Taiwan’s ITRI is now working on the development of a large amount of handling skills, and the primary unit is the Institute of Electronics and Photovoltaic Systems. Dr. Wu Zhiyi, Director of the Electro-Optical Institute, said: "Now the process of LED and display panels is relatively sophisticated. The biggest difficulty is how to handle so many μLED dies."

Dr. Wu Zhiyi pointed out that although it is not easy to produce micron-sized μLED crystals, there are still devices that can do it. Only the yield and output value problems, such as the red LED shrinking to the micron level, will be fragile, but still There is a law, and there is still no good solution for the huge amount of handling.

Because of the high skill and productivity of the huge amount of handling, Apple, Samsung and Sony are now actively discussing the breakthrough.

Dr. Wu Zhiyi showed that the principle of reaching a huge amount of handling is actually very simple, that is, a force is applied to accurately adsorb the μLED die, and then it is carried to the policy back plate, and then accurately released. The principles that can be applied are: vacuum, static electricity, adhesion, UV and electron effects.

The key question is how much the yield can reach and whether the capacity is in line with the cost.

If you don't consider the production capacity, you can also make the μLED display panel through the current handling equipment, such as the Pick-and-Place method, but the cost will be very expensive, unless the price is very insensitive to customers and applications, otherwise It is difficult to have space for commercial development.

Several companies have now announced their success on small-scale panels, including Taiwan's PlayNitride, Crystal, Apple's LuxVue, Japan's Sony, and South Korea's Samsung, but none of these companies The methods and skills for leaking their handling, of course, the output value and capacity have not been released.

At this year's CES 2018 exhibition, Samsung's 146-inch Micro LED TV "The Wall", which uses modular splicing, has reached the role of large-scale panels.

Compared with μLED, which urgently needs a huge amount of handling skills to handle its mass production, Mini LEDs with a grain size between 50 and 60 microns can be mass-produced using existing production equipment, so now LED manufacturers are The products that have been selected for this transition, and even the Micro LED products that Samsung and Sony have previously announced, may be products that are attributed to the Mini LED grade and are produced through existing equipment.

The repeated actions of these world manufacturers have certainly attracted the attention of the mall, but in the development of μLED skills, Taiwan is actually not behind, and there may be opportunities ahead. ITRI ​​started to invest in the development of μLED skills as early as 2009. At the beginning, it was not going to be used in the mainstream, but with the evolution of shopping malls and skills, it gradually realized the potential of its shopping malls.

"At the time, we thought that OLEDs can, LEDs must be able to." Dr. Wu Zhiyi said.

He pointed out that in theory, LED can replace all of the current OLED display products. The only problem is the cost of production and the so-called C/P value. If the price of the product is high and there is no interest, then there is no development. value. OLED TVs a few years ago are almost like this.

Regarding the huge handling skills, Dr. Wu Zhiyi revealed that the ITRI has already had relevant treatment plans, but he still cannot disclose the relevant information. He only responds to the relevant skills announcements this year. Please let us know. Wait.

However, he believes that the most feasible process for mass handling is still on the 6吋 to 8吋 wafers, and it is mainly used for small-scale visualization. The large-scale display can only be carried out by means of collage. The ability to deal with the problem of production costs; as for the skill method used, it will be carried by adsorption, that is, using static electricity, van der Waals or other forces to carry.

3μLED application mall will appear M-type development

Because the handling skills are not easy, and the output value and yield are limited, the use of μLED will be developed in the form of M-type, that is, starting from the two scales of extreme and minimum, and finally will gradually increase the quantity. The largest consumer electronics and television scales are carried out. But whether it can be carried out to the mainstream consumer electronics market, or even replace the current OLED TV or LCD TV, you need to pay the cost of production.

Dr. Wu Zhiyi showed that because the characteristics of LEDs are that the light-emitting area is smaller than the component area, it is very suitable to produce large-scale display panels by splicing methods, especially in the field, which may be a large-scale display of public space, plus these applications on price. The sensitivity is not high, so it will be the first commercial mall that μLED appears.

And after the super-scale, it will be ultra-small display applications, such as wearable and AR / VR devices, especially AR and VR. Dr. Wu Zhiyi showed that the high brightness, low power consumption and high response speed of μLED are very suitable for these applications. They can not only overcome the problems appearing under sunlight, but also improve the power consumption, and can also satisfy the high-speed display requirements of the game.

However, Dr. Wu Zhiyi does not think that μLED will enter the consumer electronics mall, especially the general home TV mall. He believes that the production cost of μLED is still very expensive now. Even if the process is sophisticated, it will be much higher than the LCD panel. Even if the function is excellent, it is not easy to convince consumers to purchase, so it will take some time to investigate.

But at least it is now clear that one thing is that before the huge handling skills are experienced, the products and applications of μLED are very far away from the practice of commercial malls. The fastest is the same as the second half of this year. The skill details are revealed. Before that, all of the μLEDs were probably just a vision and an argument.

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