Mass production soon? Micro LED history, current situation, principle process and participating enterprise analysis

Recently, TrendForce set of State Science and technology's LED industry research brand LEDinside (LED online) that micro LED will be mass production in 2018. In order to understand the technology development and market potential of microLED, the author makes a comprehensive analysis on the history, current situation, principle, process and enterprise of microLED.

History

Speaking of Micro LED, had to start from the display TFT-LCD backlight module application. In 1990s, when TFT-LCD began to flourish, because LED has a high color saturation, electricity, light and other characteristics, some manufacturers will use LED backlight. However, due to high cost, poor heat dissipation, low photoelectric efficiency factors, not a large number of applications in TFT-LCD products.

Until 2000, process, efficiency and cost of blue LED chips made of white LED phosphor stimulation technology began to mature; when in 2008, the white LED backlight module showing explosive growth in recent years, almost completely replaced by CCFL, the application fields of mobile phone, tablet, laptop, desktop monitors and TV etc..

However, due to the TFT-LCD non display principle caused by self luminous, the opencell penetration rate of about 7% below, the photoelectric efficiency caused by TFT-LCD is low; and the white LED can provide color saturation as RGB LED, most TFT-LCD products only about 72%NTSC; furthermore, in the outdoor environment, the brightness of TFT-LCD to ascend to 1000nits or more. The resulting images and color identification is low, it is a defect. Therefore, another direct use of the three color LED as a self luminous display dot LED Display or Micro LED technology is also developing.

Current situation

With the maturity and evolution of LED, Micro LED Display since 2010 began to have a different appearance.

From the view of the development process, Sony was published in 2012 55 "" CrystalLEDDisplay "is the type of MicroLEDDisplay technology, the resolution of the FullHD using a total of about 6 million 220 thousand (1920x1080x3) micro LED as display high resolution plan, the contrast ratio of up to one million, color saturation can be up to 140%NTSC, no reaction time and service life. However, due to the single MicroLED embedded mode, in the commercialization, there are still a lot of cost and technical bottlenecks exist, so far failed to mass production.

Although MicroLED is the theory can be applied to various sizes of products, but its yield and process from the point of view, the resolution level of demand and yield is inversely proportional, so wearable product requirements is not high on the display resolution because of the size of small size, good manufacture rate higher, accord with the requirement of saving energy, and is preferred import microLED.

General LED chip contains the substrate and the epitaxial layer thickness of about 100~500 m, and the size of 100~1000 M. The further study of the ongoing Micro Display is to LED surface thickness of about 4~5 mu m epitaxial layer with physical or chemical mechanisms stripped, and then transplanted to the circuit board on the LED.

The Micro LED Display integrated TFT-LCD and LED two technical characteristics in the development of materials, process, equipment and mature product specifications, far higher than the current TFT-LCD or OLED, more extensive applications include soft, transparent display, a plane for the next generation of display technology feasibility.

Since 2010 after the technology integration and development of various manufacturers active in Micro Display LED, LED structure, production process and drive circuit design because Micro LED Display has been the standard, manufacturers patent layout more military is a hotly contested spot.

As of 2016, has been acquired by Apple Luxvue, MikroMesa, SONY, leti and other companies have been out the size of the number of patent applications, more companies and research institutions in a number of investment related technology development.

Mainly involved in the development of enterprises

principle

Micro LED Display display principle, the LED structure design of thin film, miniaturization, array, its size is only 1-10 in M grade; after Micro LED batch transfer to the circuit substrate, the substrate can be hard, transparent, soft the opaque substrate; reuse process physical deposition complete protection layer and the upper electrode, can be carried out on board package, to complete a simple MicroLED display.

In order to be made into a display, the surface of the wafer must be made into an array structure, such as a LED display, and each of the elements must be addressable and individually driven. If the complementary metal oxide semiconductor circuit is driven by the active addressing driver architecture, the interface between the MicroLED chip and the CMOS.

After the completion of Micro LED adhesive by integrating micro lens array, improve the brightness and contrast. The Micro LED array is connected with the positive and negative electrodes of each Micro LED through a vertically staggered positive and negative grid electrode, and the Micro LED is displayed through the scanning of the electrode line to display the image.

Micro LED structure diagram

The typical structure of Micro LED is a PN junction diode, which consists of a direct gap semiconductor material. When a positive bias is applied to the upper and lower electrodes of the Micro LED, when the current is passed, the electron and the hole are combined to the active area to emit a single light. MicroLED spectra of the main wavelength of FWHM about 20nm, can provide very high color saturation, usually >120%NTSC.

And since 2008, LED photoelectric conversion efficiency has been greatly improved, more than 100lm/W has become a production standard. Therefore, the application of the Micro LED display, because of its self luminous display characteristics, with almost no light consumption components of the simple structure, can light