Comparison of COB full color and traditional SMD full color

- Mar 08, 2020-

Folding process and raw material costs

SMD full color: The cost of this product is more expensive for raw materials and more complicated production and processing technology, and the cost of investment and cost is higher.


COB full color: COB eliminates the bracket concept, no plating, no reflow soldering, no patch, and the process is reduced by 1/3. It is equivalent to SMD in die bonding and wire bonding processes, but in dispensing, separating, splitting and packaging, the efficiency of COB packaging is much higher. The labor and manufacturing costs of traditional SMD packaging account for about 15% of the cost of materials, while COB only accounts for 10%, and the cost of production is at least 5% compared to SMD full color.


Folding optical electrical

COB full color has good color consistency, large viewing angle, uniform light spot, high brightness, good color mixing effect, etc. These are the characteristics and advantages of SMD full color and dot matrix full color that cannot be surpassed.


The viewing angle is large and the brightness is high. The COB uses a heat sink process technology to ensure that the LED has an industry-leading heat lumen maintenance rate (95%). The following is a comparison of the appearance and angle of light and shape of dispensing and SMD.


COB full color appearance picture SMD full color appearance picture


COB has better visual consistency. From the appearance alone, it can be seen that there are hundreds of light emitting points on the dispensing board that are on the same PCB board, that is, on the same horizontal plane, so the light emitting points are on the same reference point, so the light spot is more uniform. However, the SMDs are affixed to the PCB board one by one, and there will definitely be high and low, so the light spot is uneven, so the visual effect is worse than the effect packaged with COB.


COB has better light quality. It can be seen from the figure below:


The traditional SMD package on the right is to mount multiple discrete devices on a PCB board to form an LED application. This method has the problems of point light, glare, and ghosting, which is obvious from the figure; and COB is an integrated package and is a surface light source, which not only has a large viewing angle of advantage 1, but also reduces the loss of light refraction.


COB has a bigger perspective. From the light chart below, we can see that the angle of view of Oreida COB full color is much larger than the angle of SMD full color. The angle of SMD full color is about 110 degrees, but the angle of view of COB full color can reach 140-170 degrees and the brightness is not Will weaken, and the vertical angle has a wide viewing angle of 140-170 degrees, these characteristics are particularly advantageous in some applications. The following is a comparison of the two light charts:


COB angle light pattern SMD angle light pattern


Judging from the actual luminous effect diagram, it is as follows:


Dispensing Glow Effect Picture SMD Glow Effect Picture


From the above comparison, the visual effect of COB full color is better than that of SMD full color, no matter from the angle of view or the light effect picture.


Folding solid crystal display

COB solid crystal display method: RGB chips are placed in a straight line. The lens above the wafer is a smooth curved surface. The lens refracts light very well. When the three-color light passes through the lens, it will be refracted and the three The color and light are mixed more uniformly, the color mixing effect is good, the light spot is uniform, which gives a good visual effect, and the display effect is more realistic. However, SMD full color does not have this feature, because the top of the SMD is a plane, so the refractive effect is average, so the color The effect is worse than COB. The following is a comparison of the light distribution curves of the two. You can see the advantages of COB full color more clearly:


COB full color R / G / B light distribution curve SMD full color R / G / B light distribution curve


From the light distribution curve chart, we can see that the three curves of COB full color have good consistency, but the SMD full color curve is not consistent. The red light curve and the blue / green light curve are greatly separated, so the effect is better than COB full color. To be worse.


Folding reliability

Low thermal resistance


The system thermal resistance of traditional SMD packaging applications is: chip-solid crystal glue-solder joints-solder paste-copper foil-insulation layer-aluminum material, and the thermal resistance of COB packaged system is: chip-solid crystal glue-aluminum material, obviously The thermal resistance of the COB package system is much lower than that of the traditional SMD package, which greatly improves the life of the LED.


In addition, Orida COB dispensing wafers are directly fixed on the PCB board, so the heat dissipation area is large, so that the junction temperature of the wafer is not easy to rise, resulting in better light attenuation and stable product quality. The SMD chip is fixed in a bowl. Not directly contacting the PCB board, and even the small heat dissipation area directly leads to poor heat dissipation performance, which will cause the junction temperature of the chip to rise, resulting in large light attenuation. These reasons are the bottlenecks in the development of SMD full-color technology.


Waterproof, moisture-proof and UV-resistant


COB uses a packaging method that is glued into a lens on the board, so when it is used outdoors, it performs better in waterproof and moisture-proof and UV-proof, while SMD generally uses a PPA material bracket, which is waterproof and moisture-proof and UV-proof. Poor, and the problems of water and moisture resistance are not solved well, it is easy to appear quality problems such as failure, dark and bright, fast decay.