Read about the next generation of mainstream display technology - Micro-LED
In the current era, display technology has become a key way of information exchange, covering smart phones, VR/AR devices, wearable products, in-car displays, tablets/computers and laser projection.
Micro LED technology is known as the "next generation mainstream display technology", its development and industrialization are accelerating, and market opportunities are increasing.
Layout of domestic leading enterprises
Tianma Microelectronics has been investing in Micro-LED technology since 2017, focusing on high PPI, high brightness and high transparency displays. The company has launched a number of industry-leading Micro-LED products.
In 2022, Tianma invested in the construction of a full-process Micro-LED production line from the massive transfer to the display module, using the laser process and customized equipment, in the case of no off-the-shelf technology in the world, to achieve fully automatic production. The line successfully lit its first production on June 26, 2024, during which more than 30 production equipment and materials were developed in partnership with supply chain companies.
On January 31, BOE Huacan Optoelectronics Zhuhai Micro LED wafer manufacturing and packaging test base project capped, the project covers an area of about 217 acres, an investment of about 2 billion yuan, will light the first product in September 2024, planned to be mass produced in December this year, the future will achieve an annual output of 58,800 Micro LED wafers.
According to data, the market size of Micro LED chips in 2023 is about 32 million US dollars, and it is expected that the global Micro LED market size in 2025 will exceed 3.5 billion US dollars by 2025, and it is expected to further break the 10 billion US dollars mark in 2027.
Micro-LED- the next generation of mainstream display technology
Micro-LED, also known as mLED or μLED, is a device composed of micron-scale electroluminescence units. Through mass transfer technology, these units can be transferred to a hard or flexible substrate and then packaged with protective layers and electrodes.
Micro-LED display principle
The core of MicroLED technology lies in its pixel structure, each pixel is composed of red, green, and blue primary color sub-pixels. Each sub-pixel can be independently controlled to precisely adjust the brightness, color and contrast of the display. In the MicroLED display system, the light emitted by each LED is processed by a lens and a mirror, and finally forms pixels on the display screen, and is adjusted by a color filter to show the desired color performance. The advantage of this technology is its ability to provide extremely high brightness, contrast and color accuracy.
Further, the Micro LED array is connected to the positive and negative poles of each Micro LED by vertically cross-arranged positive and negative grid electrodes. This connection enables the Micro LED to be lit by scanning by activating the electrode lines in a specific sequence, thus achieving image display.
Micro-LED process
Micro-LED is an LED structure that is processed by thin film, miniaturization and array, and its size is about 1-100μm. This technique involves transferring micro-leds in batches to circuit boards, which can be hard or soft, transparent or opaque. Next, a physical deposition process is used to add a protective layer and upper electrode, and finally the upper substrate is packaged to form a Micro-LED display.
Micro-LED displays are fundamentally different from traditional LED displays in terms of grain, package, integration process, backplane and drive.
Micro-LED manufacturing process mainly includes:
First, the LED crystal is thin-film, miniaturization and array through the microfabrication process technology
At present, the process miniaturization of semiconductors and chips is approaching its limit, but the Micro-LED process still has a lot of room for growth. There are three main methods used: chip level welding, epitaxial level welding and film transfer.
Chip bonding (Chip level bonding)
Chip-level welding involves splitting the LED into micron-scale Micro LED chips and bonding them to the display board using SMT or COB technology. This method can adjust the transfer spacing, but can not be transferred in batches.
SMT is widely used in the field of electronic assembly, by mounting chip components on PCB or other substrate surfaces, using reflow welding or dip welding methods such as welding assembly. The steps include material inspection, screen paste, patch, drying, reflow soldering, cleaning, plug-in, wave soldering, re-cleaning, inspection and repair.
COB is a small-pitch display technology that directly encapsulates LED wafers on the PCB and combines them into CELL units. Compared with SMD technology, COB packaging technology has its unique advantages.
Wafer bonding (epitaxial welding)
Epitaxial level welding is a method to directly form micrometer level Micro-LED epitaxial thin film structure on LED epitaxial thin film layer by inductively coupled plasma ion etching (ICP) technology. The fixed spacing of this structure is the required spacing of the display pixels.
Then, the LED wafer containing the epitaxial layer and the substrate is directly connected to the drive circuit board, and the substrate is stripped using a physical or chemical mechanism, leaving only a 4 to 5μm Micro-LED epitaxial film structure to form a display pixel on the drive circuit board. The advantage of this method is that batch transfer can be realized, but the disadvantage is that the transfer interval cannot be adjusted.
Thin film transfer Thin film transfer
The LED substrate is removed by physical or chemical means, using a temporary substrate to hold the Micro-LED film layer. Then, the micron structure is formed by inductively coupled plasma etching. Another method is to etch first and then peel off the LED substrate. According to the demand of the display point spacing of the drive circuit, the Micro-LED film is moved to the driver board in batches with the selective transfer tool to complete the display point assembly. This process is low-cost, is not limited by the size of the display board, and can be transferred on a large scale.
Second, batch transfer to circuit board - massive transfer technology
The key to Micro-LED technology is the dense integration of very small luminaires on the chip, which requires a special process - large micro-transfer (also called large transfer) technology.
The technique involves precisely soldering hundreds to thousands of primary LED grains on a small TFT circuit board, which requires an extremely high failure rate. Although there are different technologies trying to achieve this goal, mass transfer is still a technology to be mass-produced.
Mass transfer techniques fall into four categories: precision grab, self-assembly, selective release, and transfer.
In the face of increasing market demand for high-color and high-resolution screens, Micro-LED colorization has become a research focus. At present, the main implementation methods include RGB three-color LED method, UV/ blue LED light-emitting medium method and optical lens synthesis method.
As the AR/VR market continues to grow, there is a growing demand for high-performance panels that traditional LCD and OLED displays can no longer meet. The market is in urgent need of new display technologies to improve performance and meet future development standards. Micro-LED technology as an emerging solution, its characteristics make it a strong contender to meet these needs.