Product
Chip on Board is a structure that directly installs multiple LED chips on a heat dissipation PCB substrate to conduct heat directly. COB packaging combines upstream chip technology, midstream packaging technology and downstream display technology. Therefore, COB packaging requires close cooperation among upstream, midstream and downstream enterprises to promote the large-scale application of COB LED display screens. As shown in the figure, it is a COB integrated package LED display module. The front is an LED lamp module to form pixel points, the bottom is an IC driver component, and finally the COB display modules are spliced into an LED display screen of the designed size.
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 end, COB LED display modules can provide manufacturers of display screen applications with simpler and faster installation efficiency.
4. Product features: Ultra-light and thin: According to the actual needs of customers, PCB boards with a thickness ranging from 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 structural, transportation and engineering costs for customers.
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 it with epoxy resin glue. The surface of the lamp point is convex into a spherical surface, which is smooth and hard, 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 and muddy light effect.
Strong heat dissipation ability: COB products encapsulate the lamp on the PCB board, and quickly transfer the heat of the wick through the copper foil on the PCB board. In addition, the thickness of the copper foil of the PCB board has strict process requirements, and the gold sinking process will hardly cause serious light attenuation. Therefore, there are few dead lights, which greatly extends the life of the LED display.
Wear-resistant and easy to clean: The surface is smooth and hard, resistant to collision and wear; there is no mask, and dust can be cleaned with water or cloth.
All-weather excellent characteristics: triple protection treatment is adopted, with outstanding waterproof, moisture, corrosion, dust, static electricity, oxidation and ultraviolet effects; it meets all-weather working conditions and can still be used normally in a temperature difference environment of minus 30 degrees to plus 80 degrees.
It is for these reasons that COB packaging technology has been pushed to the forefront in the display field.
Current technical difficulties of COB
At present, COB needs to improve its industry accumulation and process details, and also faces some technical difficulties.
1. The one-time pass rate of packaging is not high, the contrast is low, and the maintenance cost is high.
2. Its color uniformity is far inferior to the display screen after the SMD device is mounted with light separation and color separation.
3. The existing COB packaging still uses positive chip, which requires solid crystal and wire bonding process, so there are many problems in the wire bonding link and its process difficulty is inversely proportional to the pad area.
4. Manufacturing cost: Due to the high defect rate, the manufacturing cost is far higher than that of SMD small pitch.
Based on the above reasons, although the current COB technology has made certain breakthroughs in the display field, it does not mean the complete withdrawal and decline of SMD technology. In the field of dot pitch above 1.0mm, SMD packaging technology still plays a leading role with its mature and stable product performance, extensive market practice and perfect installation and maintenance guarantee system. 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 in the range of 0.5mm~1.0mm dot pitch will reflect its technical advantages and value. To borrow a sentence from industry insiders: "COB packaging is tailor-made for dot pitch of 1.0mm and below."