The difference between SMD technology and COB technology

When it comes to LED display packaging technology, the most common ones are SMD technology and COB technology. So what are these two technologies and what are the differences? This article will take you to find out.

01
Process Introduction

The SMD technology route is to encapsulate the light-emitting chip (wafer) into a lamp bead, weld the lamp bead to the PCB board to form a unit module, and finally splice it into a whole LED screen;

The COB technology route is to directly weld the light-emitting chip (wafer) on the PCB board, and then coat the whole to form a unit module, and finally splice it into a whole LED screen.

02
Product Difference

| Image Difference

The SMD screen lamp bead is a single light source, showing a point light source effect. The COB screen has a film on the top of the light-emitting chip, and the light source becomes a surface light source after scattering and refraction. Compared with the point light source, the surface light source has a better overall visual perception, no graininess when watching, and can reduce the stimulation of the light source to the human eye, which is more suitable for long-term close-up viewing.

After the COB screen is encapsulated as a whole using a new process, the contrast can be higher, reaching more than 20000:1. The contrast of the SMD screen will not exceed 10000:1. In comparison, the viewing effect of the COB screen is closer to that of the LCD screen when viewed from the front, with bright colors and better details.

However, since the COB screen cannot sort the individual lamp beads with similar optical performance like the SMD screen, it needs to calibrate the entire screen before leaving the factory. Although the front viewing effect is excellent, it is easy to have inconsistent colors when viewed from the side at a large angle.

| Reliability Difference

The LED screen with SMD technology has weak overall protection because the light-emitting chip is encapsulated first and then mounted, and is easy to knock and drop the lamp. It has poor waterproof, moisture-proof and dust-proof performance and cannot be wiped, but it is easy to repair on site, which is conducive to later maintenance.

The LED screen with COB technology uses the chip directly mounted on the chip and then coated as a whole. The overall protection is good, and the front protection level can reach IP65. It can effectively prevent water, moisture and bumps. It can be cleaned with a wet towel, but due to the overall coating, it cannot be repaired on site and needs to be returned to the factory for repair with professional equipment, which is inconvenient.

| Energy efficiency difference

The luminous crystals in the lamp beads of mainstream SMD screen products are mostly positive-mounted processes, with leads blocking the light source, while COB screens are mostly flip-chip processes, with no light source blocking. Therefore, when the same brightness is achieved, the COB screen has lower power consumption and better economic use.

In addition, due to the low transparency of the epoxy resin used for SMD lamp bead encapsulation, the overall coating used by the COB screen has a high transparency, which further improves the economic use of the COB screen.

| Cost difference

The production process and process of SMD are relatively complex, but due to the low technical threshold, there are more than a thousand manufacturers in the country, the competition is relatively sufficient, and the technology is relatively mature.
The production process and technical threshold of COB are high, and only less than 20 manufacturers in the country have R&D and production capabilities.

COB technology is still in rapid development. Although its theoretical cost is lower than that of SMD screens, due to the low product yield, the cost of COB screens is still at a certain disadvantage compared to SMD screens with a spacing of more than 1.2.