Comparison of the Advantages and Disadvantages of SMDand COB

November 27, 2023

Comparison of the Advantages and Disadvantages of SMD and COB

 

Process introduction:

 

SMD technology route is to package the light-emitting chips (wafers) into lamp beads, weld the lamp beads to the PCB board to form a unit module, and finally splice them into a whole LED screen;

 

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

 

Image difference:

 

SMD screen light beads emit light as a single unit, presenting a point light source effect. COB screens are covered with a film on top of the light-emitting chip, and the light source becomes a surface light source after being scattered and refracted by the film. Compared with point light sources, surface light sources have a better overall visual perception, no graininess when viewed, and can reduce the stimulation of the light source to the human eyes, making them more suitable for long-term close viewing.

After the COB screen is integrally packaged using a new process, the contrast can be even higher, reaching more than 20,000:1. The contrast of the SMD screen will not exceed 10,000:1. In comparison, the viewing effect of the COB screen is closer to that of LCD when viewed from the front. screen, the colors are bright and vivid, and the details are better.

However, since COB screens cannot sort individual lamp beads with similar optical properties like SMD screens, the entire screen needs to be calibrated before leaving the factory. Although the front viewing effect is excellent, color inconsistencies are prone to occur when viewed from the side at large angles. Phenomenon.

 

Reliability differences:

 

LED screens with SMD technology, because the light-emitting chips are packaged first and then mounted, have weak overall protection and are prone to knocking off lights. They have poor waterproof, moisture-proof, and dust-proof properties and cannot be wiped. However, on-site maintenance is convenient, which is beneficial to later stages. maintain.

The LED screen with COB technology is directly chip-mounted and then fully covered with a film. 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 film coating , it cannot be repaired on site and needs to be returned to the factory for repair with professional equipment, which is more inconvenient.

 

Energy efficiency differences:

 

The luminescent wafers in the lamp beads of the mainstream products of SMD screens are mostly made of formal assembly technology, and there are leads above the light source to block them. However, COB screens are mostly made of flip-chip technology, and the light source is not blocked. Therefore, when the same brightness is reached, the power consumption of COB screens is lower and it has higher performance. Good to use and economical.

In addition, due to the low transparency of the epoxy resin used in SMD lamp bead packaging, the overall coating used in COB screens has higher transparency, further improving the economical use of COB screens.

 

Cost difference:

 

The production technology and processes of SMD are relatively complex, but due to the low technical threshold, there are more than a thousand manufacturers across the country, competition is relatively strong, and technology development is relatively mature.

COB production technology has a high technical threshold, and there are less than 20 manufacturers in the country with R&D and manufacturing capabilities.

COB technology is still developing rapidly. Although its theoretical cost is lower than that of SMD screens, due to the low product yield, the current cost of COB screens is still at a certain disadvantage compared to SMD screens with pitches above 1.2.