Analysis and evaluation of SMD packaging links

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By appdevelopment

COB packaging is to directly fix the LED chip on the pad of the lamp bead on the PCB board with conductive glue and insulating glue, and then weld the LED chip’s conduction performance. After the test is complete, it is encapsulated with epoxy resin glue.

SMD Screen packaging is to fix the LED chip on the pad of the lamp bead holder with conductive glue and insulating glue, and then weld it with the same conductivity performance as the COB package. After the performance test, it is encapsulated with an epoxy resin glue, and then the light is separated and Cutting and braiding tape, is transported to the screen factory and other processes.

Comparison of advantages and disadvantages

There is no doubt that SMD screen packaging factories can produce high-quality lamp beads, but the cost will be relatively high due to too many production processes. It will also increase the cost of transportation, material warehousing and quality control from the lamp bead packaging factory to the screen factory.

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SMD believes that COB packaging technology is too complex, and the one-time pass rate of the product is not as controllable as that of a single lamp, and is even an insurmountable obstacle. The failure point cannot be repaired and the yield rate is low.

In fact, with the current equipment technology and quality control level of COB packaging, 0.5K integrated technology can make the first pass rate reach about 70%, 1K integrated technology can reach about 50%, and 2K integrated technology can make the pass rate reach about 70%. The index reached about 30%. Even if there are modules that have not passed the first pass rate test, the number of defective points on the entire board is only 1-5. There are very few modules with more than 5 defective points. Testing and repair before sealing can improve the pass rate of the finished product. Reaching about 90%-95%. With the advancement of technology and the accumulation of experience, this indicator will continue to improve. At the same time, we also have the technology to repair bad pixels point by point after sealing.

Technical analysis and evaluation instructions:

Ease of technical implementation:

SMD packaging:

Obviously, this single lamp bead monolithic packaging technology has accumulated many years of practical experience. Each company has unique skills, scale, mature technology, and is relatively easy to implement.

COB packaging:

It is a new packaging technology that integrates multiple lamp beads. In practice, a lot of technical experience in production equipment, production process equipment, testing and detection methods, etc. is accumulated and verified through continuous innovative practice. The technical threshold is high. High difficulty. The biggest difficulty currently faced is how to improve the first pass rate of the product. COB packaging is facing a technological peak, but it is not insurmountable, but it is relatively difficult to implement.

Factory failure rate control level:

Both COB and SMD packaging can be controlled very well, and they can guarantee a zero failure rate when delivered to customers.

Cost Control:

Theoretically speaking, COB should have slightly better cost control in this link, but the current production capacity is limited and has not yet reached scale, so SMD still has the advantage for the time being.

Reliability risks:

The four-corner or hexagonal brackets used in SMD screen packaging bring technical difficulties and reliability risks to subsequent production links. For example, the reflow soldering process for lamp beads needs to solve the soldering yield problem of a large number of bracket pins. If SMD is to be applied outdoors, the outdoor protection yield problem of the bracket pins must be solved.

Because COB technology eliminates this type, there will be nearly no major specialized difficulties and trust ability pitfalls in posterior product processes. There are only two technologies faced one is how to insure that the beacon blob face doesn’t have failure points when the IC motorist chip is reflowed, and the other is how to break the problem of module essay color thickness.

Analysis and evaluation of reflow soldering process

Lamp bead surface undergoes a reflow soldering process

  1. Technical differences

Since COB packaging does not have a bracket, this process does not exist.

SMD packaging involves the display factory purchasing lamp beads from the SMD packaging factory and then patching them onto the PCB board.

  1. Some questions
  2. Competition issues

This link is different from the packaging link. The packaging link is in the middle of the industry chain, with only a handful of companies and a certain profit margin. The screen factory link is located downstream in the SMD screen industry chain. There are many companies, the technical threshold is relatively low, competition is fierce, profits are thin, and survival pressure is high. Among the many screen manufacturers, companies that have gone public through financing occupy a dominant position by virtue of their financial strength, brand advantages and foreign market channel advantages. Other small and medium-sized enterprises can only be washed away if they do not have differentiated products. The uneven development levels of enterprises will inevitably lead to the expansion of product quality differentiation. What will companies do in such an environment? How to do it? If you want to do a good job in this link and minimize the problem of reduced product reliability, the technology used may seem simple, but it is not. The following three factors deserve everyone’s attention?

The quality control level of PCB board design quality, material, manufacturing process, manufacturing process and warehousing in FS Tech.

The accuracy of SMT equipment and the quality control level of SMT production process.

In the face of market competition, managers’ cost awareness and quality awareness.

We believe that competition that reduces raw material quality and sacrifices product quality will bring disastrous consequences to the industrial chain.

  1. Product cost issues

COB packaging does not have this process, and the cost in this link is always zero.

As the dot density of SMD packaging increases, the difficulty of patch technology increases, and the cost of the product will also increase. Moreover, the higher the point density, the more the cost increases, showing a non-linear relationship of accelerating growth.

  1. Reliability issues

COB packaging does not have this process, and there is no reliability reduction problem in this link.

Outdoor SMD Screen packaging generally has four solder pins per bracket, so there must be a problem of reduced reliability in this link. This is determined by reliability theory. According to the principle of reliability, the fewer control links a product has, the higher its reliability.

SMD packaging generally has four solder legs per bracket, so there must be a problem of reduced reliability (trust ability) in this link. This is determined by reliability (trust ability) theory. According to the principle of reliability (trust ability), the smaller control links a product has, the advanced its reliability (trust ability).

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