COB VS GOB LED DISPLAY

GOB VS SMD

GOB LED display technology can be applied in various ways to protect LED displays from damage and reduce maintenance costs. This technology is especially useful for rental LED screens, which are frequently moved and require a high level of protection. such as GOB small-pitch LED displays, GOB flexible LED displays, GOB rental LED displays, GOB floor LED screens, and irregular-shaped GOB LED displays. It can provide waterproof, shockproof, and dustproof protection to ensure that these LED displays remain in good condition.

However, GOB is not a breakthrough in packaging technology, but rather a process improvement to the existing SMD surface mount, which essentially still belongs to the SMD Family. We would rather call it GOM “Glue on Module”.

Compared with SMD, due to the surface coating, GOB’s protection performance has been enhanced, but still fails to improve the display performance.

COB VS GOB

GOB has most of features of the SMD.

1. COB LED screen offers a stunningly high color contrast ratio of 10,000:1, much higher than the regular black SMD LED‘s 5,000:1 contrast ratio. GOB can increast the SMD’s contrast ratio up to 100000:1

2. COB LED modules have a water and moisture-proof rating of IP65 in the front, and IP30 at the back, which allows them to be used even in extreme conditions such as ice water or 100-degree boiling water, providing perfect protection in wet and cold regions, such as Russia.

3. The optical design features a high fill factor and small pixel factor, a “surface light source” emission, a matte coating, a high contrast, reduced glare, and effective resistance to blue light, which can effectively reduce the appearance of moiré. It is particularly suitable for high-end applications such as studios, weather forecast halls, traffic halls, satellite command centers, and broadcasting centers.

4. The COB LED module has an epoxy resin coating on its surface. As the pixel pitch is small, the components are sealed to the PCB, which prevents them from being exposed. This makes the LED display screen resistant to damage and falling off from collisions, as well as being dust-proof, waterproof, moisture-proof, and UV-proof.

6. COB packaging technology has a small pixel density, allowing for an ultra-wide 180° viewing angle. Refraction light losses are minimal, allowing for the same viewing angle experience from any position facing the center of the screen, ensuring consistency of color and brightness no matter the angle.

SMD‘s require reflow soldering, which, when the solder paste reaches a temperature of 240°c, causes an 80% weight loss of the epoxy resin, resulting in the glue easily separating from the LED cup. In contrast, COB technology does not require reflow soldering and thus is more stable. Additionally, solder paste does not need to pass through ROHS approval.

In summary:

1. GOB is not LED chip-level packaging technology, only a 1.0 version of the LED display panel manufacturing technology in the industry chain downstream display factory after the SMT process of a panel protection process.
2. The GOB display panel is an SMD display panel, still can not solve all the problems of the bracket technology.
3. Although the GOB display panel can improve the hard body protection ability and appearance consistency of surface lamp beads, the resulting internal stress release problem, heat dissipation problem, repair problem, adhesive material flame retardant problem, and adhesive affinity problem will deteriorate the working performance of display panel.
4. In actual outdoor cases there has been a large area of cracked glue, peeling, and poor protection performance problems.

GOB is an improvement of traditional SMD technology, it can be used for all pitch displays, and for certain applications that require high-level protection of the LED.

 On the other hand, COB display is currently mainly used in the small pitch LED display P0.4~P1.5. This pitch range screen now is also called a Mini LED display. with the decreasing cost of COB. COB technology will be also the mainstream solution for micro-pitch displays in the future. 

Visionpi’s GOB LED Display 

What is Mini LED and Micro LED led display?

The Micro-LED concept was first put forward in 2000. In 2017, Mini-LED, as a subordinate form of Micro-LED, was introduced as a groundbreaking product, officially opening a new chapter of Mini and Micro-LED.

Definitions of Mini/Micro-LED vary in the industry. On one hand, upstream suppliers and LCD display manufacturers tend to define Mini-LED and Micro-LED by chip size, formal or flip structure, and film transfer (substrate-less structure). On the other hand, large-format display manufacturers are more inclined to define Mini-LED and Micro-LED by pixel pitch and packaging method.

I1.In terms of pixel pitch. products at or below 2.5mm are defined as fine-pitch, which serves as an umbrella term. Within the fine-pitch range, Mini-LED is defined as products with pixel pitch ranging from 0.4mm to 1mm, whereas Micro-LED is defined as products with pixel pitch below 0.4mm.

2 In terms of packaging. fine-pitch displays (typically below 1mm) made of IMD and COB are considered Mini-LED displays. Micro LED is powered by COB technology and COG technology.

LED displays have been used in commercial applications for more than a decade. IMD extends the service life of the SMD supply chain and serves as a smooth transition from SMD to finer-pitch products. COB’s growth paves the way for Mini- and Micro-LED products in the future.

3.In terms of Chip Size. Mini LEDs tend to measure below 200 microns , while micro LEDs can be as small as 100 microns, or 0.004 inches.

Market competition brought by Mini & Micro-LED

With LED displays evolving to the fine-pitch level, viewing distance is also greatly reduced, which broadens the applications for fine-pitch LED displays. Indoor LED displays start at 4mm, and fine-pitch products start from 2.5mm. Further finer pitch in the sub-1 mm range will bring LED displays to the consumer market and ultimately compete against LCD and laser projections in the TV market.

Take the 108-inch LED display as an example (600*337.5mm LED panels in 4×4 panel array). When the pixel pitch is P1.25, P0.62, and P0.31, the resolution can be 2K, 4K, and 8K respectively. According to the Rec. ITU-R BT.1769 reference standard of ITU (International Telecommunication Union), the optimal horizontal viewing angle under this resolution is 32°, 58°and 96°respectively, from which the optimal viewing distances are estimated to be 4.17m,2.02m and 1.01m respectively. The above viewing distance makes it possible for LED displays to be used in living rooms as a TV. The viewing distance of 2.02m and 1.01m is suitable for the living room area of most houses. From another perspective, if we convert the resolution of 2K and 4K LCD TVs into pixel pitches of 53” LED displays, we can find that 2K LCD TV’s pixel pitch is between 0.6mm and 1.2mm, and 4K LED TV’s pixel pitch is between 0.3mm and 0.5mm. Up to now, SONY, Samsung, and other display manufacturers have launched large-size Mini/Micro-LED display products up to 120 inches based on a modular design. If we ignore their sky-high price, these products are perfect for living room applications. 

Common Anode LED Display

Common anode LED screen has all of the anodes of the individual LEDs connected together and to a common terminal, while the cathodes of each LED are connected separately.

Common Cathode LED Display

A common cathode LED screen is also called” energy-saving led display”. It has all of the cathodes of the individual LEDs connected together and to a common terminal, while the anodes of each LED are connected separately.

common cathode”. It is an energy-saving power supply technology for LED displays where the current first passes through the LED chips and then reaches the negative pole of the driving IC, hence the name “common cathode”. The voltage drop and current loss can be reduced by using the independent voltages power supply method. Additionally, this technology can separate and precisely power the red, green, and blue LED chips. LED professionals know that the rated power required for the red, green, and blue chips is different, and ordinary power supply methods cannot separate them and can only provide them with the same power. With an independent voltage power supply, the red, green, and blue LED chips can be separately and accurately powered, providing different voltages to them under the same current, which can ensure that they work at their rated power, thereby improving energy utilization and reducing energy consumption.

Common Cathode Fine Pixel Outdoor LED Display

Common Cathode VS Common Anode LED display, which is better?

In the early stage, LED displays were mostly used for outdoor applications using larger pitch products, which did not have a physical space limit for driver ICs as they were designed with static scan drive. However, when LED displays began to be used for indoor applications using smaller pitch products, the space available for electronic components was squeezed, and as a result, dynamic scan drive (line-scanning drive) based on time-division multiplexing (TDM) came into being.

Under line-scanning drive mode, LED displays can be categorized into two types: the common cathode and the common anode.

As the name implies, common anode means individual LEDs are connected via their positive ends and driven by negative ends; and common cathode means individual LEDs are connected via their negative ends and driven by positive ends, and in common cathode mode, R, G, B chips are separately powered with voltage and current precisely distributed to red, green, and red diodes, and the current passes the diodes then to the negative ends of ICs.

Common Cathode VS Common Anode LED Schematic Diagram

The difference between the common cathode and common Anode

The direction of the current flow

■ In common anode mode, the current of LED displays flows from PCB to LED diodes, and the RGB LEDs are powered with the same power source at the same power rate, and therefore the forward voltage drop is increased.

■ In common cathode mode, the LED display’s current first passes through LED diodes with R, G, and B LEDs separately powered. Voltage and current are precisely distributed based on individual needs, then to the negative ends of ICs. The forward voltage drop is reduced, and as a result, there is less internal conduction resistance.

The supply voltage

■ In common anode mode, the LED display provides RGB LEDs with a unified voltage higher than 3.8V (such as 5V), therefore the power consumption is high.

■ In common cathode mode, the LED display provides RGB LEDs with separate voltage based on actual needs (2.8V for the red LED, and 3.8V for the green and blue LEDs). Because of this separate and precise power supply, the power efficiency is higher. Consequently, less heat is produced as less power is consumed.

 Energy efficiency and cooling effect

■ Based on accurate power control, common cathode technology can reduce the power consumption of the entire system by reducing the red LEDs’ supply voltage. Moreover, there are no extra line-scanning devices needed to achieve this. By using common cathode technology, LED displays can reduce excessive heat and power consumption, pixel failure rate, and ghost lines (tailing effect), thus improving LED displays’ overall performance

Supply chain

■ Common cathode technology reduces forward voltage drop by reducing the supply voltage of red LEDs, however, this requires the use of more power supplies, which further increases the complexity of the component layout on PCBs. Currently, the key supporting components related to common cathode technology are LED diodes, power supplies, and driver ICs. These components have market-proven solutions for common anode technology but are still in the early stages of common cathode technology.

How to calculate the power consumption of led display

Assuming that under common anode mode, a 5V voltage is used as the unified power, under common cathode mode a 2.8V is used for red LEDs, and all other conditions are the same if the current of red LEDs accounts for 40% of the total current, then we can quickly calculate the percentage of power saved: 40%*(5-2.8)/5=17.6%. If the ed LED current accounts for 50% of the total current, then we can save 50%*(5-2.8)/5=22%, Therefore, there is a theoretical 17.6%~22% power savings using common cathode technology over common anode technology.

Common Cathode LED Display saving cost.

•  1). Electricity, save operating costs: accurate power supply to reduce led display power loss, reduce operating costs.

•  2). No-cooling systems required: low heat temperature rise can also save the air conditioning, fans, and other cooling equipment.

•  3). Maintenance and repair costs: the subsequent fully enclosed die-casting aluminum chassis, the components are maintained one by one, making the led display life is about 2 times that of ordinary screens.

Common Cathode Energy-saving LED Display

Common Cathode COB LED Screen

Ultra-low power consumption & temperature riseThe indoor common cathode LED screen can effectively save energy and dissipate heat through the flip-chip LED plus common cathode drive.

Common Cathode Outdoor Fine Pitch LED Display

The Common Cathode Outdoor Fine Pitch LED Display series, with pixel pitches of 1.2mm, 1.5mm, 1.8mm, and 2.5mm, provides unmatched clarity and durability for outdoor environments. Utilizing cutting-edge common cathode technology, these displays significantly reduce power consumption and heat output, all while maintaining high brightness levels. This ensures reliable, long-lasting performance, even in the most demanding outdoor conditions. Whether for advertising, events, or architectural installations, these displays offer vibrant, high-definition visuals with exceptional stability.