What are the pros and cons of COB LED Screen?

COB LED Screen packaging technology has great advantages compared with SMD packaging technology.

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Its pros: smaller space of LED beads, better protection performance, long service life, and low dead light rate.

Its cons: difficulty in manufacturing finished products, maintenance inconvenience.

The so-called COB package, that is, the chip-on-board package, is actually a kind of LED chip pasted on the PCB substrate. This new packaging technology is distinct from SMD packaging technology, streamlining the entire packaging process and eliminating the need for original support and reflow processes. As a result, the entire LED becomes more stable, with reduced point spacing that directly improves the resolution of the LED display.

Advantage Analysis

• The distance between points can be smaller

One of the standout features of COB packaging technology is its ability to decrease the spacing between LED beads. With SMD packaged LED displays previously limited to a minimum pitch of P1.2 (1.2mm), achieving a minimal dead light rate was challenging. The encapsulated COB technology, however, alters the layout and configuration of LED beads, significantly reducing the dot pitch and achieving resolutions comparable to those of LCD splicing screens.

• Better protection performance

In LED displays with closer spacing, external forces during transportation and installation can easily dislodge light beads, leading to individual pixels that won’t emit light or display monochrome, which is often dependent on the encapsulation technology. Since with COB technology the LED chip is directly encapsulated in a recess of the PCB lamp and bonded with epoxy resin, the entire lamp is composed of a raised, smooth sphere that offers enhanced protection.

• Long service life and low dead light rate

The COB package embeds the LED lamp on the PCB board, allowing for efficient heat transfer through the board’s copper foil. This process is subject to strict requirements, and with the use of gold plating, serious light attenuation is nearly eliminated. Consequently, this greatly extends the lifespan of the LED display.

Disadvantage Analysis

• Difficulty in manufacturing finished products

When encapsulating the LED display with COB, it's essential to ensure that each lamp is free from defects before assembly, making the process far more demanding than conventional SMD packaging, where individual bulbs can be replaced.

• Maintenance inconvenience

In a traditional SMD package, it is possible to disassemble the unit board for repairs on individual bulbs. However, with COB products, maintenance restricts the ability to ameliorate surrounding lamps, making it particularly challenging. Despite the superior protection of COB, there remains a certain dead light rate, necessitating the entire replacement of the unit board in many cases.

Every packaging technology arises from necessity and fulfills a specific role, even if it comes with certain imperfections. As technology advances, the drawbacks associated with COB will likely diminish. To sum up, COB LED screen technology represents a future-oriented development, especially due to its compact packaging, which is crucial for users seeking high resolution.

What are CoB LEDs?

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A CoB LED (or chip-on-board LED) is defined as a singular device featuring multiple LED chips mounted on an efficient thermal substrate coated uniformly with phosphor.

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Those who traverse through retail spaces or homes with track or recessed lighting are likely experiencing light from CoB LEDs. Their prevalent use arises from their capability to emit bright white light from a compact source, along with impressive efficiency across a variety of applications.

So, how is a CoB LED constructed, and how does it differ from other LED types?

CoB (chip-on-board) signifies the construction method of the LED unit, which includes the following critical elements:

• An electrical power supply that provides the energy to the LED
• The light-emitting chip or “die”, typically made from indium gallium nitride (InGaN), which emits blue light photons when activated
• A phosphor coating that converts blue light to white; its chemical composition can be modified to achieve a specific color temperature.

CoB LED: Space-Saving Array of Multiple LED Chips

A CoB LED integrates numerous LED chips onto a thermally efficient substrate, resulting in a compact design. Each chip is a bare die, which enables very close placement on the substrate. This proximity allows for higher intensity and light density from a smaller area contrasted with single packaged LEDs. The manufacturer then applies a uniform phosphor coating across the entire chip array to achieve the desired white color temperature.

Advantages of a CoB LED

A single CoB LED can comprise hundreds of chips arranged in a dense configuration. This setup enables CoB LEDs to produce substantial light output from a compact area, surpassing the potential of an array of packaged LEDs.

This single LED setup leads to a more straightforward design and product, along with optical benefits related to uniform light and efficient optics.

Regarding electrical design, a CoB LED requires only a singular two-wire power supply for the entire chip array, simplifying the installation process. In contrast, an array of packaged LEDs demands dedicated power supply traces for each individual LED unit.

The production process benefits too, as fewer units need to be soldered to the board when utilizing a CoB LED instead of a collection of packaged LEDs.

Optically, various reflector optics can be employed with CoBs of different sizes to establish the direction and breadth of the beam, as seen in spot or flood lamps.

Finally, the color consistency of a CoB LED is likely improved since a singular phosphor coating covers the entire chip array, while an array of packaged LEDs features individual phosphor coatings for each unit.

For more insights, please visit COB LED Sustainability.

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