The advantages and disadvantages of COB package LED display and its development difficulties

COB packaging integrates upstream chip technology, midstream packaging technology and downstream display technology. Therefore, COB packaging requires close cooperation between upstream, midstream and downstream companies to promote the large-scale application of COB LED displays.

It is a COB integrated package LED display module. The front side is the LED lamp module to form the pixel point, the bottom is the IC driving element, and finally the COB display modules are spliced ‚Äč‚Äčinto a design size LED display screen.

The theoretical advantages of COB:

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

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 a simpler and faster installation efficiency for the display application manufacturers.

4. Product features:

(1) Ultra-light and thin: According to the actual needs of customers, PCB boards with a thickness of 0.4-1.2mm can be used to reduce the weight to at least 1/3 of the original traditional products, which can significantly reduce the structure, transportation and engineering costs for customers.

(2) Anti-collision and pressure resistance: COB products directly encapsulate the LED chip in the concave lamp position of the PCB board, and then encapsulate and cure with epoxy resin glue. The surface of the lamp point is raised into a spherical surface, which is smooth and hard, and is resistant to impact grind.

(3) Large viewing angle: The viewing angle is greater than 175 degrees, close to 180 degrees, and has a better optical diffuse color and muddy light effect.

(4) Strong heat dissipation: COB products encapsulate the lamp on the PCB board, and quickly dissipate the heat of the lamp wick through the copper foil on the PCB board, and the thickness of the copper foil on the PCB board has strict process requirements, plus the sinking Gold process, almost no serious light attenuation. Therefore, there are few dead lights, which greatly prolongs the life of the LED display.

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

(6) Excellent all-weather characteristics: It adopts triple protection treatment, and the effects of waterproof, damp, rot, dust, static electricity, oxidation and ultraviolet are outstanding; it meets all-weather working conditions, and the temperature difference environment of minus 30 degrees to minus 80 degrees can still be used normally.

It is for these reasons that COB packaging technology has been pushed to the forefront in the display field.

Current COB technical difficulties:

At present, COB’s accumulation in the industry and process details need to be improved, and it also faces some technical problems.

1. The one-time pass rate of the package is not high, the contrast ratio is low, and the maintenance cost is high;

2. The uniformity of color rendering is far inferior to that of the display screen after the SMD device using the spectroscopic color separation.

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

4. Manufacturing cost: Due to the high defect rate, the manufacturing cost far exceeds the small spacing of SMD.

Based on the above reasons, although the current COB technology has made certain breakthroughs in the display field, it does not mean that SMD technology has completely withdrawn. The market practice and perfect installation and maintenance guarantee system are still the leading role, and it is also the most suitable selection direction for users and the market.

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 range of 0.5mm~1.0mm point spacing. : “COB package is tailor-made for 1.0mm and below dot pitch”.