Talking about the Advantages and Disadvantages of COB Package LED Display Technology and Its Technical Development Difficulties

A chip on board is a structure in which a plurality of LED chips are directly mounted on a heat dissipation PCB substrate to directly conduct heat. The COB package integrates upstream chip technology, midstream packaging technology and downstream display technology. Therefore, COB packaging requires close cooperation between upstream, downstream and downstream enterprises to promote large-scale application of COB LED displays. As shown in the above figure, it is a COB integrated package LED display module. The front side is the LED light module to form the pixel point, the bottom is the IC drive component, and finally one COB display module is spliced ​​into the design size LED display.

The theoretical advantages of COB:

1. Design and development: Without the diameter of a single lamp body, it can be made smaller in theory;

2. Technical process: reduce the cost of the bracket and simplify the manufacturing process, reduce the thermal resistance of the chip, and achieve high-density packaging;

3. Engineering installation: From the application side, the COB LED display module can provide simpler and faster installation efficiency for the manufacturer of the display application.

4, product characteristics: ultra-thin: according to the actual needs of customers, the thickness of the PCB from 0.4-1.2mm thickness, so that the weight is reduced to at least 1/3 of the original traditional products, can significantly reduce the structure, transportation and customers Engineering costs.

Anti-collision and compression: The COB product directly encapsulates the LED chip in the concave lamp position of the PCB board, and then is cured by epoxy resin. The surface of the lamp point is convex into a spherical surface, which is smooth and hard, and is resistant to collision and wear.

Large viewing angle: The viewing angle is greater than 175 degrees, close to 180 degrees, and has a better optical diffuse color glare effect.

Strong heat dissipation: COB products are packaged on the PCB board, and the heat of the wick is quickly transmitted through the copper foil on the PCB board. The thickness of the copper foil of the PCB board has strict technical requirements, plus the immersion gold process. Hardly causing severe light attenuation. Therefore, there are very few dead lights, which greatly extend the life of the LED display.

Wear-resistant, easy to clean: the surface is smooth and hard, collision-resistant and wear-resistant; no mask, dust can be cleaned with water or cloth.

All-weather excellent features: triple protection, waterproof, moisture, rot, dust, static electricity, oxidation, UV effect; meet the all-weather working conditions, the temperature difference between minus 30 degrees and zero 80 degrees can still be used normally.

For these reasons, COB packaging technology has been pushed to the forefront in the display field. LED manufacturers represented by Hida Electronics, Vory Zhuohua, and Alida have successively launched their own COB package display products, which can provide targeted customized product solutions for different customers and market needs.

Current COB technical challenges:

At present, the accumulation of COB in the industry and the details of the process need to be improved, and also face some technical problems.

1. The primary pass rate of the package is not high, the contrast is low, and the maintenance cost is high;

2, its color uniformity is far less than the display after the SMD device patch with the separation of color separation.

3. The existing COB package still uses a positive-loading chip, which requires a solid crystal and wire bonding process. Therefore, there are many problems in the wire bonding process and the process difficulty is inversely proportional to the pad area.

4, manufacturing costs: due to high defect rate, resulting in manufacturing costs far exceed SMD small spacing.

Based on the above reasons, although the current COB technology has made certain breakthroughs in the display field, it does not mean that the SMD technology has completely withdrawn. In the field of point spacing of 1.0mm or more, SMD packaging technology relies on its mature and stable product performance and extensive. The market practice and perfect installation and maintenance guarantee system are still the dominant role, and the most suitable selection direction for users and markets. With the gradual improvement of COB product technology and the further evolution of market demand, the large-scale application of COB packaging technology will reflect its technical advantages and value in the interval of 0.5mm~1.0mm, which is borrowed from the industry. "The COB package is tailored to 1.0mm and below."

With the unremitting efforts of advanced manufacturers represented by Hida Electronics and Vorey Zhuohua, we expect COB technology to enter the field of 1.0mm or less as soon as possible to solve the technical problems faced and completely renew the advantages of COB products.