At the end of May, a wave from the semiconductor industry sparked renewed interest in glass substrates. Due to their use as packaging substrates in the LED industry, COG (Chip On Glass) technology gained attention. While the broader industry’s interest in COG may have been brief, within the LED sector, COG packaging has remained a hot topic.
The high thermal conductivity, low thermal expansion coefficient, resistance to low temperatures, impact resistance, high electrical connection density, high flatness, and ability to support complex wiring make glass-based COG packaging an ideal fit for key production steps in Micro/Mini LED technology. These attributes suggest that COG packaging could help reduce the costs of Micro/Mini LED technology and expand its applications in consumer electronics such as home televisions and tablets. Currently, two types of glass substrates are used for COG packaging: TFT glass and TGV glass.
However, due to the difficulties in repairing glass substrates and the challenge of achieving economies of scale, COG has yet to become a mainstream Micro/Mini LED packaging technology.
In reality, all packaging technologies, including COG, have their advantages and disadvantages. Thus, the discussion around COG in the LED industry extends beyond the technology’s specific characteristics and future potential. It centers on how companies should position themselves among COG, COB, MiP, and SMD packaging technologies to secure a competitive edge in the Micro/Mini LED race.
Overview of COG, COB, SMD, and MiP Technologies
From a corporate perspective, the key considerations when selecting a packaging technology are how well it aligns with the company’s advantages and strategies, and how many opportunities and challenges lie ahead. The industry’s packaging landscape currently includes four main technologies: COG, COB, SMD, and MiP.
SMD/IMD
Compared to other packaging methods, SMD (Surface Mounted Devices) has been around for a long time and is one of the most commonly used technologies in the LED industry. SMD involves securing the LED chip to the solder pad of the lamp bead bracket with conductive and insulating adhesives, then encapsulating it with epoxy resin before undergoing light separation, cutting, and taping for shipment to the display factory.
In terms of pixel structure, traditional SMD packaging typically contains only one pixel, making it unsuitable for smaller pitch products. IMD (Integrated Matrix Devices), considered an upgraded version of SMD, addresses this limitation by integrating four or more pixels into one package. This reduces the pixel pitch while improving production efficiency, display quality, and protective performance.
MiP
MiP (Micro LED in Package) is a chip-level packaging technology in which Micro LED chips are mass-transferred onto a carrier board before being encapsulated, cut, tested, and mixed. One key feature of MiP is its compatibility with existing SMD production equipment, reducing the need for heavy capital investments by manufacturers.
COB
COB (Chip On Board) is a no-bracket packaging technology that integrates multiple lamp beads directly onto a PCB board, bypassing the need for the complex SMT surface-mount process. This simplifies the manufacturing process and improves production efficiency while providing finer display quality.
COG
COG (Chip On Glass) is an upgraded version of COB, replacing the PCB board with a glass substrate. The glass substrate’s flatness and ability to support complex wiring simplify mass transfer and reduce process errors.
The Industry’s Multi-Track Packaging Strategy
LED companies have increasingly adopted a diversified approach to packaging technology, driven by the need to find an optimal balance between display performance and cost in the era of Micro/Mini LED technology and small-pitch displays.
A look at ten well-known LED packaging/module and display manufacturers shows that most have adopted flexible dual or multi-technology packaging strategies. COB, MiP, and SMD are the primary focuses of many companies.
SMD
SMD remains a staple for many companies due to its long history of development, standardized production processes, equipment, and materials, which ensure product stability and cost-effectiveness. SMD continues to be a major revenue source for companies like Nationstar, Kinglight, Leyard, Absen, Unilumin, and Colent.
However, despite SMD’s maturity, it is losing ground to technologies like COB, particularly in the small-pitch market. Companies are responding by reducing SMD production capacity and shifting focus to newer technologies.
COB
COB’s ongoing encroachment on SMD market share can be attributed to its more streamlined production process, which binds RGB chips directly to a PCB board, reducing material costs and allowing for smaller pixel pitches. Moreover, COB offers superior protection, reduced panel thickness, better heat dissipation, and improved light quality compared to SMD.
Driven by these advantages, COB production capacity continues to expand rapidly across the industry, with major companies significantly increasing their COB investments.
MiP
Although MiP is a relatively new technology, companies are making aggressive moves to develop MiP products and capacity. Kinglight believes that MiP offers pixel pitches comparable to COB but with superior display performance, making it a strong contender in the high-end display market.
COG
Currently, LED display manufacturers are still in the exploratory phase with COG packaging technology, and progress has not yet matched that of COB and MiP. Some companies, such as Leyard, are collaborating with panel manufacturers to develop COG solutions, while others, like Unilumin and Absen, are still in the early stages of technical exploration.
Conclusion
LED companies are adopting diversified packaging strategies, with SMD providing cost-effective, mature solutions, while COB and MiP are gaining traction as next-generation technologies aimed at small-pitch displays. Though COG holds theoretical advantages, its development remains in its infancy. Over the next few years, COB and MiP are expected to dominate various pitch applications, driving growth in the LED display market.
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