COB and SMD packaging technology analysis and evaluation |
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| Reading Volume： 【 1896 】 | Time： 【 2017-11-07 】 | |
| Package analysis and evaluation 1. Different technologies COB packaging is to directly fix the LED chip with conductive glue and insulating glue on the soldering pad of the lamp bead on the PCB board, and then weld the conduction performance of the LED chip. After the test is completed, it is encapsulated with epoxy resin. The SMD package is to fix the LED chip on the pad of the lamp bead holder with conductive glue and insulating glue, and then use the same conduction performance as the COB package to weld. After the performance test, it is encapsulated with epoxy resin, and then split, Cutting and braiding, transportation to the screen factory and other processes. 2. Views from both sides There is no doubt that SMD packaging factories can produce high-quality lamp beads, but the production process is too much and the cost will be relatively high. It will also increase the cost of transportation, material storage and quality control from the lamp bead packaging factory to the screen factory. SMD believes that the COB packaging technology is too complicated, and the one-time pass rate of the product is not well controlled by a single lamp, and it is even an insurmountable obstacle. The failure point cannot be repaired and the yield is low. We believe that with the current level of equipment technology and quality control for COB packaging, 0.5K integrated technology can achieve a pass rate of about 70%, 1K integrated technology can reach about 50%, and 2K integrated technology can make this This indicator reaches about 30%. Even if there are modules that have not passed the first pass rate test, the defective points of the whole board are only 1-5 points, and there are few modules with more than 5 defective points. Testing and repairing before sealing can make the finished product pass rate It reaches about 90%-95%. With the advancement of technology and accumulation of experience, this indicator will continue to improve. At the same time, we also have a point-by-point repair technology for the dead pixels after sealing. Ease of technical realization: SMD packaging: Obviously, this single lamp bead monomer packaging technology has accumulated many years of practical experience. Each company has unique skills, scales, and mature technology. It is relatively easy to implement. COB sub-assembly: It is a new packaging technology that integrates multiple lamp beads. In practice, many technical experiences in production equipment, production process equipment, testing and inspection methods are accumulated and verified in continuous innovation practice, and the technical threshold Difficulty. The biggest difficulty currently facing 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 zero failure rate can be guaranteed when handed over to the customer. Cost Control Theoretically speaking, COB's cost control in this link should be slightly better, but the current production capacity is limited and scale has not yet formed, so for the time being, SMD still has the advantage. Reliability hazards The four-corner or hexagonal bracket used in the SMD package brings technical difficulties and reliability risks to the subsequent production links. For example, the reflow soldering process of the lamp bead surface needs to solve the problem of a huge number of bracket pin soldering yield. If SMD is to be applied outdoors, the outdoor protection yield problem of the bracket pins must be solved. The COB technology is precisely because this bracket is omitted, there will be almost no major technical difficulties and reliability risks in the subsequent production links. There are only two technical hills: one is how to ensure that the lamp bead surface does not show failure points when the IC driver chip surface is reflowed, and the other is how to solve the problem of module ink color consistency. |
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