In recent years, Micro LED has been regarded as a new generation of display panel technology after LCD and OLED due to its low power consumption, fast response, long life and high light efficiency. The full English name of Micro LED is Micro Light Emitting Diode, which is called Micro Light Emitting Diode in Chinese. It can also be written as μLED. It thins, miniaturizes and matrixes traditional LEDs, reducing the pixel distance from millimeters to micrometers. , And highly integrated solid self-luminous display technology on a chip. The biggest difference from conventional LEDs is the size. The size is equivalent to 1/10 of the human hair, and the volume reaches 1% of the mainstream LED size. However, the pixel size is currently still There is no uniform definition.
Micro LED's micron-level pixel pitch can make it cover multiple application scenarios from small and medium size displays to medium and large size displays. Compared with traditional small-pitch LEDs, due to the reduced size, the display resolution and image quality are significantly improved. The optical design can make the viewing angle wider, the contrast higher, and the image quality better. It is suitable for virtual reality, small projectors, and micro Various display scenarios such as monitors, visible light communication, medical research, etc. Compared with OLED, it adopts self-luminous technology to display, allowing the integration of sensors and circuits to achieve embedded sensing functions, and it can also be combined with flexible substrates to achieve flexible display, which can be used for wearable/implantable devices and vehicle displays. In addition, Micro LED has high definition, high brightness, good contrast, and high response speed. It is very suitable for VR, AR and other wearable devices that have high requirements for response speed (high brightness and power saving are suitable for outdoor wear Occasion) application.
The concept of Micro LED display began in 2000 until 2012. After Sony showed off the first Crystal-LED microLED TV, Micro LED displays appeared in the business world. Different research institutions and companies began to focus on miniaturization and full color. Bottleneck technologies such as wafer transfer, etc. According to the size of the display panel for different applications, the preparation of the display can be divided into monolithic manufacturing technology and mass transfer technology. Monolithic manufacturing technology refers to the direct production of Micro LED on Si, GaN or Sapphire substrates. For high-resolution displays, the LED is bonded to the terminal display substrate, and finally the substrate is peeled off by a physical or chemical mechanism. This method avoids the complicated massive transfer process, but it is also limited to the construction of smaller displays, such as near-eye displays, smart watches and other micro displays, which limits the application scenarios of Micro LED; in addition, each process can only be on the substrate One color of the lamp bead chip is grown, so this single-chip manufacturing technology cannot solve the RGB full-color display. The quantum dot full-color display proposed in recent years uses the light emitted by a single ultraviolet Micro LED to excite the red, green and blue luminescent medium covered by the upper layer to achieve full color. This colorization alternative technology may fill in the future. The limitations of monolithic manufacturing in terms of full color. Another manufacturing technology is mass transfer. The LED chip is grown on the source substrate, and then the LED is separated from the source substrate and the chip is quickly, accurately and reliably transferred to the display electronic device through a certain force. For a wider range of display applications such as mobile phones, flat panels and TVs, the separation from the substrate after the production on the substrate is complete, inevitably requires a massive transfer method to transfer the Micro LED chip to a larger size and with logic circuits. Assemble on the substrate to meet application requirements. In addition, the use of flexible and stretchable optoelectronic devices for wearable and bioelectronic applications has recently gained widespread research and popularity. These applications require the transfer of LEDs to flexible substrates and also require massive transfers to be achieved. However, due to the extremely small size and huge number of wafers transferred each time, the accuracy and speed requirements of the transfer process are very high, which has become a key technology restricting the mass production of Micro LEDs.
