2 Minutes to Know More About COB LED Display

COB technology is an emerging LED packaging technology, which is different from traditional SMD surface mount packaging. So what are the advantages and disadvantages of COB LED display? How is it different from the SMD LED screen?

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1. What is a COB LED display?

COB, Chip on Board, is a technology that is used to encapsulate a chip on a board.

Unlike SMD, where the beads are soldered to the PCB, the COB process first covers the silicon placement point with thermally conductive epoxy resin (silver-doped epoxy resin) on the substrate surface, then the LED chip is attached to the interconnected substrate with conductive or non-conductive adhesive through adhesive or solder.

Finally, the chip is electrically interconnected with the PCB board through lead (gold wire) bonding.

The LED wafer is fixed to the front surface of the display substrate and the film is pasted to the front surface of the display substrate, the LED wafer is a common red, green, or blue LED chip to achieve integrated packaging.

The COB packaging process breaks through the traditional packaging technology’s dependence on brackets and supports. So it reduces the number of soldering points.

The fewer welds, the fewer points of failure. Therefore, the stability and reliability of the COB LED module are high, and the failure rate of the lamp surface is low.

cob led display

2. What are the Features of the COB LED Display?

1. different packaging methods;

2. ultra-micro pitch;

3. ultra-clear display screen;

4. the box is lighter and thinner than led small pitch;

5. small thermal resistance value, strong heat dissipation;

6. effective suppression of moiré, light sense superior;

7. small spacing, resulting in the screen ink color consistency is not beautiful;

8. the production process steps less, and the current stage of packaging technology needs to be improved;

9.COB display technology requirements are high, COB display manufacturers less;

3. SMD vs COB LED, Which is Better?

Many customers who come into LEDs often hear about COB technology, which makes them confused about its differences from traditional LED displays.

In fact, what we are talking about is COB, which is an emerging packaging technology for LED displays.

In the past, LED displays used SMD surface mount packaging, so the comparison between COB displays and LED displays actually refers to the comparison between SMD packaging and COB packaging. What are the differences between the two?

3.1 Comparison between COB and SMD LED Display

(1) Different Packaging Technology

Nowadays, our conventional LED display screens use surface-mount SMD packaging.

This packaging technology involves fixing the LED chip through a bracket, curing it with epoxy resin inside, and then fixing it on the PCB board with solder paste, followed by reflow soldering to evenly arrange the LED beads on the board.

However, this technology process is cumbersome, requires a certain amount of operation time, and the minimum distance between points can only be 1.2, even if it is multi in one, it can be done to a smaller size, But still unable to get rid of the problem of losing the lights.

COB packaging simplifies the packaging process of LED chips by directly integrating them onto the PCB board and fixing them with adhesive.

The entire process is simpler, without the need for reflow soldering, and the LED chips are more stable. At the same time, the spacing between points can also be smaller.

COB VS SMD

SMD is short for Surface Mounted Devices, where the LED packaging factory uses the SMD process to fix the bare chip to the holder, connect the two electrically via gold wire and finally protect them with epoxy resin.

SMD encapsulated small pitch products generally have the LED beads exposed or use a mask. SMD uses surface mount technology (SMT), which is highly automated and has the advantages of small size, large scattering angle, good luminous uniformity and high reliability.

The COB screen is a led screen made using the COB packaging method, while we now often say that the led screen is the use of SMD packaging led screen, the difference between the two is that the packaging method is different.

(2) Different Pixel Pitches

Ordinary SMD packaged LED displays are limited by packaging technology, and their point spacing is usually above P1.2, such as P1.2, P1.56, P1.875, P2.0, P3, P4, and so on.

Products with small spacing are affected by welding technology, and there may be phenomena such as light bead detachment.

Its development limitation is mainly that it cannot achieve point spacing below 1.0, resulting in the inability to further improve the screen resolution,

If it is a situation that requires high clarity in image quality, it is not very suitable.

The display screen packaged with COB can achieve smaller dot spacing, for example, the P1.2, PO.9, and PO.6 products .

pixel pitch difference

(3) Production Cost

There are many steps in the production process of SMD LED, and the production cost is high.

Based on SMD, COB LED screen eliminates the concept of brackets, and does not have production processes such as electroplating, patching, and reflow soldering, which simplifies the production process.

The process of SMD LED display is mature, but the COB process is not popular yet, so the price of SMD LED products is cheaper than that of COB products.

(4) Product Reliability

According to the principle of reliability, the fewer control links a product has, the higher its reliability. The product reliability of the COB package is higher.

In the production, transportation, and installation of traditional LED display screens, due to the fact that the lamp beads are exposed to the surface, the lamp beads will fall off when touched by fingers or collide with other things during installation, resulting in a certain pixel not lighting up.

This is mainly because the lamp beads are welded to the PCB board, and collision can easily cause the lamp to fall out.

If you want to repair it later, you can only have technical personnel come to the site to weld or directly replace the unit board, Causing a high after-sales rate.

The display screen packaged with COB has better protective performance, and it will not cause the lamp beads to fall during installation and use, so its surface is also more collision resistant and its stability is greatly improved.

led display packaging

(5) Optical Properties

The SMD package pastes the LED lights one by one on the PCB board, which makes the light spot uneven.

The COB display uses glue dispensing to package the light-emitting chips on the same horizontal plane, making the light-emitting surface more uniform.

In addition, the COB LED video wall has good color consistency, a viewing angle close to 175°, and a good color mixing effect.

(6) Light Quality

The SMD package attaches multiple devices to the PCB, which may cause glare and ghosting. COB LED screen is an integrated package. It reduces light refraction.

Basically, the main difference between COB displays and LED displays is the above three points.

From the perspective of industry development, COB screens will be the mainstream direction in the future.

Compared with traditional surface mount technology displays, COB displays have many advantages such as high reliability, low cost, small spacing, wear resistance, impact resistance, and strong heat dissipation ability.

Compared to led screens, COB screens have a smaller pitch, better protection, and better heat dissipation.

In COB packaging and SMD packaging, COB packaging devices are completely enclosed, while SMD packaging devices are exposed on the screen surface, and COB packaging process steps are fewer.

4. What are the Advantages of COB LED Screen?

(1) Smaller Pixel Pitch

The COB LED screen can easily achieve a smaller pitch, making the display screen clearer, more delicate, and softer in color.

The technological characteristics of SMD limit the breakthrough of display screens to micro-pitch products to a certain extent.

The advent of COB technology has made small-pitch LED displays more possible.

There is no physical barrier between the light-emitting chips, and the display pixels in the unit are more, the picture is clearer, and the color is more delicate.

(2) Super-high Protection Ability

The high-protection COB LED screen completely encapsulates the device in the PCB board.

In the process of transportation, installation, and disassembly, there will be no bad phenomena such as falling lamps and broken lamps.

From leaving the factory to when the product is put into use, the ultra-high protection capability can protect the product from damage and reduce product loss.

(3) Better Display Effect

The “surface” light source emits light, effectively suppressing moiré, and not hurting the eyes when viewed at close range.

The COB small display screen has full display pixels and a visual effect comparable to that of an LCD screen.

The screen can reduce light refraction, and the color is better.

Excellent visual effects make it a high-quality choice for high-end display fields, such as high-end conference rooms, studios, command and dispatch centers, etc.

COB LED display screen

(4) More Convenient Maintenance

Due to the rigorous packaging of COB, the COB LED screen requires almost no maintenance after it is put into use.

The daily maintenance of SMD LED displays requires special attention, such as module maintenance and screen cleaning.

For SMD LED displays with large pitches or small pitch products with masks, improper cleaning will cause damage.

In comparison, the daily maintenance of COB screens is more convenient. Simply clean the surface of the screen with a rag.

COB LED uses epoxy resin to package the chip on the PCB, the screen is smooth, strong sealing, and impervious to water.

(5) Strong Heat Dissipation

The heat directly passes through the PCB board without accumulation, and the product life is more guaranteed.

5. What are the Disadvantages of COB LED?

1. COB LED screen is a new display product, the current packaging technology is not perfect SMD technology, high technical requirements, and high research and development costs;

2. SMD packaging process production steps have differences, enterprises in the transition will be separated from the original production base, high cost of enterprise transformation, and manufacturers less;

3. 2mm below the point pitch led display, whether it is SMD or COB, screen ink color consistency needs to be strictly controlled;

4. COB screen price than the same point pitch led display 10-20% higher.

Know more information about DIP, SMD, COB LED displays, you can turn to this post:

DIP LED Module VS SMD VS COB? One Article Tells You.

6. More About Flip Chip COB LED

In the ever-growing micro-pitch display market below P1.0mm, COB has natural advantages over SMD and GOB LED displays.

COB has also become one of the core technology routes in small-pitch products.

With the advancement of chip packaging technology, COB technology has been differentiated into two types: front-mount chip and flip-chip.

Flip-chip GOB has attracted industry attention because of its ability to achieve chip-level gaps.

(1) Front-mount Chip VS Flip chip GOB

What is an LED front-mount chip?

A front-mount chip means that the electrode and the light-emitting surface of the chip are on the same side. The electrodes are connected to the substrate by wire bonding.

flip chip cob led

What is LED Flip Chip?

The light-emitting surface of the flip-chip faces up, and the electrode faces down, which is equivalent to inverting the front-mounted chip.

The advantages of flip-chip: no need for wiring, higher stability; high luminous efficiency, low energy consumption; large positive and negative spacing, effectively reducing the risk of lamp bead failure.

(2) Why Flip-chip COB LEDs are the Future of Display?

The flip-chip COB further improves product performance based on COB technology. As an upgraded product of formal COB, the COB Flie chip LED display can realize the true chip-level gap.

Overall, the advantages of flip-chip COB LEDs and people’s consumer demand for displays make it the future of the display industry.

Consumers are pursuing better visual quality, better viewing angles, and better near-screen experience. Flip-chip COB can meet these needs.

Ultra-high reliability

Thinner and lighter packages have reduced thermal resistance and improved display life. Ultra-high protection is reflected in waterproof, anti-collision, shockproof, dustproof, and antistatic.

Excellent display effect

20000:1 ultra-high contrast ratio and more light and dark contrast details bring a better visual experience. HDR digital image technology makes static and high-dynamic picture quality fine and perfect.

Ultra-small dot pitch

The cob flip chip has a higher pixel density and is the first choice for products with a pixel pitch below 1.0mm.

Super energy-saving and comfortable

Under the same brightness conditions, flip chip cob power consumption is reduced by 45%. Good viewing angle and side-view display uniformity are suitable for indoor near-screen experience application scenarios.

7. Conclusion

COB LED video wall has the characteristics of light and thin, anti-collision and pressure resistance, and good display effect, and has great advantages in the field of small-pitch display.

Although there are still some technical difficulties to be overcome, it is undeniable that COB LED display will bring more possibilities to the display industry in the future.

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