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  • Micro LED, Mini LED, COB, GOB, TOPCOB...
    Oct 13, 2018

    Micro LED, Mini LED, COB, GOB, TOPCOB... This dazzling letter name, what is the specific meaning? How to distinguish? And these new words that are endless, which represent the birth of innovative technology, or the market hype of merchants bluffing?


    This article will start with a simple chart to clarify the meaning, technical origin, and innovative gold content of various nouns.


    The following table, from three basic elements, is used to evaluate small-pitch products. These three elements are:


    1, chip size


    2, point spacing


    3. Technical route


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


    1539229797921071876.jpg


    Noun: Micro LED


    Definition: Chip size is less than 50um


    The Micro LED is a hot word with a very high frequency. In general, the 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 above 100um. Therefore, in order to challenge the existing technology, Micro LED is also more strictly defined as the chip is less than 20um or 30um.


    When the chip size is below 50 um, 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 118 um * 118 um (micron).


    At present, Micro LED technology is still in the research and development stage. In addition to the chip's miniature technology, how to transfer a large number of micron-sized chips to the circuit board is the biggest technical bottleneck of Micro LED. However, there is no doubt that breakthroughs in this field are new technologies of epoch-making significance.


    Noun: Mini LED


    Narrow sense: chip size 50-100um


    Generalized: Point spacing is less than P1.0


    Mini LED was originally proposed by chip manufacturers for the first time. Because the implementation of Micro LED technology takes a long time. At the same time, for most of our large-screen displays, in most applications, the pixel density does not need to reach the micron level. Therefore, the Mini LED is larger than the Micro LED, and the chip size is larger and technically easier to implement.


    Initially, Mini LEDs were defined to be more stringent, with chip sizes falling between 50 and 100 um. This size of chip can only be achieved with flip chip technology. It should be said that the initial definition of the Mini LED is still a great breakthrough in the technical length.


    However, as the heat of micro-pitch LEDs continues to rise, manufacturers in the domestic display industry have called the Mini LEDs with a dot pitch of 1.0 mm or less because of the need to promote 'hotness'. Such a title is extremely confusing. Because the traditional surface mount package can also be used below P1.0, it can also be used in N-in-1 package. It can also be done by using the COB package of the front-loading chip. Of course, the same can be done by flip-chip COB. Therefore, the domestic display of the name of the Mini LED, many of which have not broken through in the chip technology, are still widely used in small-pitch LED display chips.


    For example, the N-integrated package introduced by some domestic packaging factories still uses more than 100um chips, and the package technology is also SMD surface-mount package technology. It integrates a set of 1R1G1B chips in a single package into 4 groups, 6 groups or 9 groups. It should be said that N-in-one is an extension of the extension and improvement of traditional SMD packaging technology. It is not a new generation of technology.


    Noun: COB


    Qualitative: Intergenerational replacement of packaging technology routes


    Highlights: Flip COB point spacing can be as small as P0.1


    COB is the abbreviation of English CHIP ON BOARD. It is an innovation of the existing SMD package mode, and it is also a change of SMD small pitch LED.


    The COB package is to directly bond the chip to the PCB board and then protect it by the lamination technology. In the SMD mode, the chip is fixed, soldered, and dispensed into a separate lamp bead, and then soldered to the PCB through the surface mount. The two package structures are shown below:

    1539229797997077476.jpg

    Technical innovation, OR market speculation, a picture to understand the new term


    The COB package completely eliminates the SMD bracket or substrate and has a simpler structure. At the same time, because there is no exposed soldering feet, it is not affected by the external environment, which greatly improves the sealing performance of the entire display structure. Therefore, the COB package can greatly improve the reliability and stability of small-pitch LEDs. At the same time, COB technology can achieve smaller spacing and lower material costs. It is a subversion of the traditional SMD approach.


    At present, there are two types of COB: a compact chip COB and a flip chip COB.


    The minimum point spacing that can be achieved with a COB is $0.5. The flip-chip COB can also reduce the wires of the chip and the substrate shown in the above figure. Flip the COB to further reduce the dot pitch to P0.1.


    The most representative products of the inverted COB, one is the CLEDIS display that Sony displayed at major exhibitions, and the other is the THEWALL display with P0.84 dot pitch introduced by Samsung. It can be said that in the future, flip-chip COB represents the advancement and development direction of small-pitch LEDs.


    Noun: GOB


    Qualitative: existing SMD surface stickers small spacing improved version


    GOB is the abbreviation of GLUE ON BOARD, which is on the surface of the surface display module, and then a layer of integral coating to improve the sealing of the SMD surface. It is an improvement on the existing SMD form stickers.


    It should be said that GOB is a technological improvement of display manufacturers, which improves the moisture-proof, waterproof and anti-collision performance of the display. To a certain extent, it compensates for the lack of reliability and stability of the surface-mounted small-pitch display. Defects. However, this technical solution puts very high demands on the SMD surface-mounting process. Once there is a virtual welding, it is difficult to repair. Moreover, it is time to verify whether the colloid has discoloration, degumming, and heat dissipation during long-term use.


    Noun: TOPCOB


    Qualitative: existing SMD surface stickers small spacing improved version


    This product called TOPCOB has nothing to do with the COB we usually call. It still uses the existing SMD surface mount package, and then the module surface is glued, which is exactly the same as the GOB technology mentioned above. It is a patch to the surface mount technology defect, and it is difficult to call it a revolutionary intergenerational product.