Korean media: LG Display is developing Micro LED inspection and repair technology

On March 17, according to Korean media The Elec, LG Display has been participating in the Micro LED testing and repair national R&D project promoted by the Ministry of Industry, Trade and Energy since April last year.

The R&D project is jointly participated by Ulsan University of Science and Technology (UNIST), Korea Display Industry Association, Hubio and Justem. As a panel manufacturer, LG Display is responsible for process validation and performance evaluation. The project adopts a model in which equipment manufacturers and research institutions develop inspection and rework process technologies, while LG Display verifies them from the perspective of actual production applications.

Micro LED displays are made by transferring and arranging hundreds of thousands to millions of ultra-small LED chips onto a substrate. Unlike OLED, which uses organic matter, it uses inorganic light-emitting elements, which perform well in terms of brightness, lifespan and energy efficiency, and is regarded as the next generation display technology. However, due to the high difficulty of the process, there may be defective pixels in which some chips cannot work properly during the mass production process. Since the pixel size is only on the 5-100 micron level, dead pixels will inevitably appear during the manufacturing process.

Therefore, in the Micro LED production process, detection technology to detect defective pixels and rework technology to replace or repair defective pixels are crucial. Traditional electroluminescence (EL) detection methods require physical contact and run the risk of damaging the chip. Although the photoluminescence (PL) method based on optical technology can achieve non-contact detection, it has limitations due to low accuracy.

Industry analysts believe it is imperative to develop technologies that combine inspection and rework processes. Even assuming a high-resolution panel yield of 99.99%, tens of thousands of defective pixels may still occur, which means that the efficiency of the inspection and rework process is directly related to production efficiency.

Relevant people in the display industry said: "Due to the characteristics of the manufacturing process, it is inevitable for Micro LED to have defective pixels. Inspection and rework technology is the process of discovering and replacing these pixels, which plays an important role in ensuring yield."

In order to realize the commercialization of Micro LED, the stability of the overall process technology including transfer, bonding, inspection and rework must be ensured. In particular, inspection and rework technology are considered key factors that determine both yield and manufacturing costs. Another person in the display industry explained: "Ensuring rework technology has a greater impact on reducing production costs than directly accelerating commercialization. Because when the yield rate is improved, the overall manufacturing cost will be reduced."

It is also worth mentioning that as a superior project, the "Inorganic Light-Emitting (iLED) Display Technology Development Ecosystem Construction Project" was promoted from last year to 2032, with a total investment scale of 484 billion won. Inorganic light-emitting display is a concept covering next-generation light-emitting technologies, including Micro LED.

The specific topics of this project include "Technology Development for Inspection and Rework of Chip-Replaceable Small and Medium-sized Micro LED Display Panels" and "Technology Development for Inspection and Rework of Chip-Non-Replaceable Panels". The execution time of each task is approximately 45 months.