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What is LED Small Spacing?

source: Shenzhen HighMight Technology Co., Ltd popularity:98 Date of publication:2023/12/08 14:40:28 small middle big

Micro LED、 Mini LED、 COB 、GOB、 TOPCOB...... What is the meaning of this bewildering list of letters? How can I tell the difference? Which of these new terms represent the birth of innovative technologies, or are they bluffing market hype?

The popularity of small-pitch LED technology in the commercial market has greatly encouraged the R&D boom of manufacturers and spawned the continuous emergence of many innovative technologies and products. At the same time, the new terms that have come one after another are also dizzying. The promotion of each new term is an endorsement or proof that the product has the significance of changing the dynasty. It seems that with a lofty name, this technology has epoch-making significance.

In fact, the realization of every revolutionary innovative technology and product is difficult to achieve overnight, it requires a painstaking and long process of exploration, during which there will be some transitional intermediate technologies and products. As far as these intermediate technologies and products themselves are concerned, they also have a certain degree of progressive significance. However, sometimes merchants exaggerate the propaganda and consciously package various terms, which has caused disruption and misleading to the market.

In this article, we will start with a simple diagram to clarify the meanings of various terms, their technical origins, and their innovative content.

The following table evaluates and classifies small-pitch products from three basic elements. The three elements are:

1. Chip size

2. Dot spacing

3. Technical route

Using these three basic elements, the technical content of a product can be measured more accurately.

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Noun: Micro LED

Definition: The chip size is less than 50um

Micro LED is a buzzword that comes up very frequently. Generally speaking, the current industry-recognized standard is that when the chip size of the display is less than 50um, it can be called Micro LED technology. At present, the conventional small-pitch LED display chip size is more than 100um. Therefore, in order to challenge the existing technology, Micro LED is also more strictly defined as a chip less than 20um or 30um.

When the magnitude of the chip size is less than 50um, the pixel pitch is also defined in the order of microns. For example, when the pixel density of a mobile phone is 432 PPI, the pixel pitch is 118um * 118um (microns).

At present, Micro LED technology is still in the research and development stage. In addition to the miniature technology of chips, how to transfer a large number of micron-level chips to the circuit substrate is the biggest technical bottleneck of Micro LED. However, there is no doubt that the breakthrough in this field is a new technology of epoch-making significance.


Noun: Mini LED

Narrow sense: chip size 50-100um

Generalized:pixel pitch ess than P1.0

Mini LED was first proposed by chip manufacturers. Because it will take a long time for Micro LED technology to be realized. At the same time, for our large-screen displays, in most application scenarios, the pixel density does not need to reach the micron level. Therefore, compared with Micro LED, Mini LED has a larger chip size and is technically easier to implement.


Initially, Mini LEDs were strictly defined, with chip sizes ranging from 50 – 100 um, which could only be achieved with flip chip technology. It should be said that the original definition of Mini LED has made a great breakthrough in technology.

However, with the continuous rise of the popularity of micro-pitch LED, manufacturers in the domestic display industry have put the display screen with a dot pitch of less than 1.0mm because of the need for market promotion, also known as Mini LED. Such a title can be confusing. Because, the traditional surface-mount package can also be used to achieve P1.0 or less, the N-in-1 package can also be used, the full-chip COB package can also be used, and of course, the flip COB can also be done. Therefore, many of the displays known as Mini LED in China have not made a breakthrough in chip technology, and they are still widely used in chips for small-pitch LED displays.

For example, the N-in-one integrated packaging launched by some domestic packaging factories still uses chips greater than 100um, and the technical route of packaging is still SMD surface mount packaging technology. It is a group of chips that were originally packaged in a single package, 1R1G1B, and integrated into 4 groups, 6 groups, or 9 groups. It should be said that N-in-1 is an exploration of the extension and improvement of traditional SMD packaging technology. It's not about upgrading technology.


Noun: COB


Qualitative: Generational replacement of packaging technology routes


Highlights: The minimum point spacing of flip COB can reach P0.1

COB is the abbreviation of CHIP ON BOARD, which is an innovation of the existing SMD packaging mode, and can also be called a replacement of SMD small pitch LED.

COB packaging is to wire the chip directly on the PCB board, and then protect it through adhesive technology. In the SMD method, the chip bonding, wire bonding, and dispensing are first packaged into an independent lamp bead, and then soldered on the PCB board through surface mounting. The two package configurations are shown in the figure below:

 

The COB package completely eliminates the bracket or substrate of the SMD, and the structure is more concise. At the same time, because there are no exposed welding feet, it is not affected by the external environment, which greatly improves the sealing of the entire display structure. Therefore, COB packaging can greatly improve the reliability and stability of small-pitch LEDs. At the same time, COB technology can also achieve smaller pitches and lower material costs. It is a subversion of the traditional SMD method.
At present, there are two types of COB: full-chip COB and flip-chip COB.

The minimum dot spacing that can be achieved by a full-size COB is P0.5. Flip COB can also reduce the wires between the chip and the substrate as shown in the figure above. Flip COB further reduces the dot spacing to P0.1.

The most representative products of flip COB are the CLEDIS display displayed by Sony at major exhibitions, and the other is the P0.84 dot pitch THEWALL display launched by Samsung. It can be said that in the coming period, flip COB represents the way forward and the direction of development of small pitch LEDs.

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Sony CLEDIS display

 

SAMSUNG THEWALL DISPLAY

Noun: GOB

Qualitative: Improved version of the existing SMD surface mount with small spacing


GOB is the abbreviation of GLUE ON BOARD, which is a layer of overall glue on the surface of the surface mount display module to improve the sealing performance of the SMD surface mount. It is an improvement on the existing SMD surface mount.
It should be said that GOB is a technological improvement of display manufacturers, which improves the moisture-proof, waterproof and impact-proof performance of the display, and to a certain extent, makes up for the lack of reliability and stability of the surface-mounted small-pitch display. However, this technical solution puts forward extremely high requirements for the SMD surface mount process, and it is difficult to repair once there is virtual soldering. In addition, it also takes time to verify whether the colloid will have discoloration, degumming, and affect heat dissipation during long-term use.
Noun: TOPCOB
Qualitative: Improved version of the existing SMD surface mount with small spacing
This product, called TOPCOB, has nothing to do with what we usually call COB. It still uses the existing SMD surface mount package, and then the module is covered with adhesive, which is exactly the same as the GOB technology mentioned above. It is a patch to the defects of surface-mount technology, and it can hardly be called a revolutionary intergenerational product.
Shenzhen Highmight Technology Co., Ltd. was established in 2010, since its establishment 12 years has been focusing on the field of LED applications, is a collection of design, production, sales and service as one of the LED video display high-tech enterprises, now has more than 100 authorized national patents. In 2020, Guangzhou Branch was established to further improve Highmight national sales layout and after-sales service system. The company adheres to the business philosophy of "customer-oriented, collective efforts, and pursuit of excellence", and provides value-for-money LED video large-screen products and solutions for global audio-visual customers.