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The Rise of COB Technology in LED Displays

In the ever-evolving world of display technology, the COB (Chip on Board) technology has been quietly shaping the future of direct-view LED displays since its inception in 2012. 

What is COB technology?

COB technology is a leap toward perfection. By directly bonding RGB chips onto a PCB (Printed Circuit Board) and encapsulating them with a protective layer, COB technology offers a robust solution that shields delicate LED chips from external damage. This ingenious approach not only enhances durability but also allows for the creation of finer pixel pitches below 1.0mm, opening up a new realm of high-resolution displays.

What are the benefits of COB?

The advantages of COB technology are many, but here are the highlights that set it apart from traditional SMD (Surface Mounted Device) LED displays:

  • Micro Precision: Achieve pixel pitches below 1.0mm for incredibly detailed images.
  • Durability: COB’s encapsulation method offers superior protection, making displays more resistant to impacts and the elements.
  • Lightweight Design: Thinner and lighter modules mean easier installation and transportation.
  • Outdoor Resilience: Withstand harsh outdoor conditions without compromising display quality.
  • Heat Management: Efficient heat dissipation ensures a longer lifespan for the display.
  • Visual Comfort: A uniform light source that reduces eye strain, making it ideal for close viewing.

COB panels utilize this advanced process to create LED display modules that rival traditional LCD panels in versatility and quality. By adopting a standardization approach similar to the LCD industry, COB technology aims to unify a fragmented market, ensuring cost efficiency and superior performance across the board.

A Comparative Glance at LED Technologies

Since 2012 the fine-pitch LED industry has experienced rapid growth, covering a wide range of applications from P2.5 to P1.25 pixel pitches. Traditional LED displays primarily utilized discrete SMD (Surface Mounted Device) technology. However, as the pixel pitch decreased, this technology faced increasing challenges. New technological approaches, such as IMD (Integrated Matrix Device), MiP (Micro LED in Package), and COB (Chip on Board), have emerged to address the limitations of discrete devices to some extent, yet each has its own set of drawbacks and none has completely outperformed the others. Currently, manufacturers are selecting different technological paths based on their resources and capabilities.

  1. IMD (Integrated Matrix Device)

IMD technology integrates multiple pixel structures within a single packaging unit, with the four-in-one technique being the most mature application. Still utilizing surface-mount technology, IMD’s traditional SMD packaging typically represents one pixel; COB packaging involves directly encapsulating LED chips onto the module’s baseboard, covering each large unit as a whole, which contains hundreds to thousands of pixels. The “four-in-one” LED module, essentially consisting of four basic pixel structures made up of 12 RGB-LED chips, remains surface-mounted. With advancements, packaging manufacturers may develop “six-in-one” or even “N-in-one” solutions.

IMD continues the mature selection technology of small pitches, allowing for precise selection of devices based on wavelength and brightness. This uniformity before taping helps avoid minor differences during packaging that could lead to color discrepancies, ensuring better color consistency. COB packaging, however, cannot perform light and color separation for each pixel unit within the module, leading to slight variations due to factors like different batches of glue, board thickness, mixing ratios, and the fluidity of the resin at high temperatures.

  1. MiP (Micro LED in Package)

MiP is a chip-level packaging technology where Micro LED chips are massively transferred to a carrier board, encapsulated directly, and then cut and tested for color mixing. This process eliminates defective beads upfront, eliminating the need for later repairs; Micro LED beads are then placed on tape or blue film for the display manufacturer to create modules.

Theoretically, the MiP approach is compatible with traditional SMT equipment, allowing display manufacturers to maintain their existing production chains and save on new equipment costs. MiP products do not require customized development, offering high compatibility across applications, such as P0.6 to P1.25 pitches. Due to the smaller chip size, the utilization rate of wafers per unit area significantly increases, potentially reducing the cost of LED chips. Unlike the COB approach, which requires secondary selection, MiP can perform selection and color mixing in one go, facilitating easier defect detection and repair, improving uniformity, and reducing the cost of secondary selection.

  1. COB vs. IMD vs. MiP

COB panels have significant advantages in terms of product attributes, but the lack of a rich ecosystem has been a major limitation. Historically, fewer companies have participated in the COB pathway compared to SMD, resulting in a smaller industry scale and higher costs than the IMD approach.

From the perspective of cost curves, the SMD/IMD industry largely relies on existing ecosystems, requiring little additional R&D and capital expenditure. Consequently, their average cost curves are almost independent of industry scale, showing no significant variation with changes in scale.

One major advantage of MiP technology is the direct use of Micro LED chips, which, due to their smaller size, offer potential material cost savings. While downstream application manufacturers can continue using existing patch production lines, packaging or module manufacturers need to invest in more precise production and testing equipment. Compared to COB technology, this requires much less initial investment, as illustrated by the blue cost curve.

Producing COB requires additional investment in equipment capable of sorting chips, as well as significant capital in specialized fixed assets such as die bonding machines, printers, and AOI (Automatic Optical Inspection) equipment. Therefore, a sufficiently large sales volume is necessary to amortize the fixed costs, giving COB a clear cost advantage.

Thus, as production scales up, the average cost of MiP can decrease, but at a slower rate than COB. Assuming the industry continues to expand, COB ultimately has a relative cost advantage.

  1. Virtual Pixels Enhance COB’s Competitive Edge

Virtual pixels, also known as shared or dynamic pixels, allow each LED to serve multiple pixel points, such as in 2/3/4/6/8x schemes. For example, in a 4x scheme, pixels quadruple the physical pixel count by rapidly distributing them across odd and even rows and columns, effectively halving the distance and quadrupling the resolution compared to traditional displays.

For an 8K LED display, combining additional green light LED chips (RGBG) with sub-pixel multiplexing technology theoretically quadruples the resolution, enabling 8K display effects on a 4K structure and significantly reducing production costs.

Despite the less granular appearance compared to real pixels, the enhanced pixel algorithms minimize perceivable differences from a distance, offering nearly equivalent display quality and user experience at significantly reduced costs. This gives COB an advantage over competing technologies.

COB and MiP are newer technologies benefiting from reduced unit area costs as the industry scales. If COB first adopts virtual pixel display technology, it will move to a more advantageous cost position, quickly achieving cost benefits and market share.

In summary, at any production scale and specified pixel pitch, COB can achieve lower costs per square meter, allowing COB to gain cost advantage at lower industry scales and accelerate the replacement of traditional direct display technologies.

The Future Is Bright for COB Technology

The potential market for COB panels is vast, with significant growth opportunities if costs can be reduced through innovations like virtual pixel technology. As COB technology continues to evolve, it promises to capture a substantial share of the consumer market, bringing high-quality LED displays into homes and businesses worldwide.

Despite the rapid advancements and the challenges of high capital investment, COB technology’s journey from a niche innovation to a potential market leader is a testament to the dynamic nature of technology adoption. With its ability to offer standardized, mass-produced, and cost-effective solutions, COB is not just a part of the future of display technology—it is the future.