Technology | Comparison between COB display and traditional SMD display

Today, with the rapid development of LED display technology, COB (Chip on Board) and SMD (Surface Mount Device), as two major mainstream packaging technologies, are reshaping the industry landscape with their differentiated advantages. This article will conduct an in-depth comparison from the dimensions of technical principles, display effects, protective performance, and application scenarios, revealing the role division between the two in high-end displays and popular applications.

1. Technical principle: The leap from "discrete devices" to "integrated packaging"

SMD technology involves encapsulating LED chips into individual beads, which are then fixed to a PCB board via reflow soldering, forming a point light source display unit. This technology boasts a high level of maturity, but due to the limitations of the bead holder structure, the minimum dot spacing typically stops at P1.2, making it difficult to break through physical limits. On the other hand, COB technology employs a "direct chip attachment + overall potting" process, where RGB chips are directly bonded to a PCB substrate and fully encapsulated with polymer materials, completely eliminating the need for holders and solder joints. This design enables the dot spacing to be compressed to the P0.4 level, increasing the pixel density per unit area by 300%, providing hardware support for 8K ultra-high-definition displays.

2.Display Effect: Revolution in Surface Light Sources and Leap in Image Quality

The point light source characteristic of SMD leads to a granular appearance when viewed closely, especially in products with a pitch below P1.5, where the Moire interference problem is prominent. However, COB, through its surface light source emission technology coupled with a micro-lens array design, enables light to be evenly diffused through the resin layer, achieving a 170° ultra-wide viewing angle and an ultra-high contrast ratio of 20000:1. In scenarios such as studios and command centers, the color reproduction (ΔE<1.5) and brightness uniformity (>98%) of COB displays are close to the level of liquid crystal displays, effectively eliminating the common issues of color cast and dark areas found in SMD products.

3.Protective Performance: From "Fragile LED Beads" to "Military-Grade Protection"

The exposed structure of SMD LED beads limits its protection level to IP30, making it prone to issues such as falling or dead lights during transportation vibrations, humid environments, or cleaning operations. In contrast, the fully sealed packaging design of COB, certified with IP65 protection, can withstand an impact energy of 5J (equivalent to a 5kg weight falling from a height of 1 meter), and its moisture, dust, and anti-static performance is improved by 10 times. In a large concert in 2024, the COB display screen maintained normal display even after being washed by heavy rain, while the SMD screen used during the same period experienced a 30% failure rate of LED beads, highlighting the reliability advantage of COB in harsh environments.

4.Application Scenario: Differentiated Demand Drives Technological Divergence

Leveraging its cost advantage (15-20% lower price compared to products of the same specification) and mature industrial chain, SMD still dominates outdoor advertising, sports venues, and other long-distance viewing scenarios. Its modular design supports rapid replacement, reducing maintenance costs by 60% compared to COB. On the other hand, COB focuses on the high-end market. In scenarios such as smart city command centers and medical imaging diagnosis, its seamless splicing and low blue light (RG0 exemption level) characteristics have become rigid demands. According to industry data, COB's market share in the small-pitch market below P1.0 has exceeded 45% in 2025, and it is expected to account for 70% of the high-end display market share by 2027.

5.Technological evolution: Future prospects from competition to integration

Currently, COB is breaking through the yield bottleneck through Flip Chip technology and mass transfer processes, while SMD is enhancing reliability through GOB (Glue on Board) protective coatings. It is noteworthy that the rise of Micro LED technology is blurring the boundaries between the two - the integrated packaging concept of COB and the precision manufacturing process of SMD will achieve deep integration in the third-generation display technology. It is predicted that by 2028, COB and improved SMD (such as Mini SMD) will jointly occupy 80% of the LED display market, driving the industry towards higher definition and greater intelligence.

From technical principles to application ecosystems, the essence of competition between COB and SMD lies in the display industry's eternal pursuit of "performance limits" and "cost efficiency". With the advent of the 5G+8K era, COB's dominance in the high-end market will continue to grow, while SMD will maintain its position in popularization through technological innovation. Together, the two are writing an epic tale of the evolution of LED display technology.