Interpretation of COB Packaging Technology
COB packaging technology has been classified as a free package or province package mode, but this package is not to save the packaging link, but to save the packaging process, and patch technology compared to COB packaging process to save To a few steps, to a certain extent, save time and technology, but also to a certain extent, save the cost. SMD production process needs to go through solid crystal, wire, dispensing, baking, stamping, color separation, taping, patch and other links, and COB process on this basis to simplify, first IC will be attached to the circuit board Then solid crystal, wire, test, dispensing, baking, become finished.
On the production process alone, it took a few steps, the industry said that this way, you can save a large part of the cost. It is worth noting that the COB package does not require reflow soldering, which has become one of the advantages of COB.
Conventional packaging is the lamp beads on the PCB board for welding, lights more and more dense when the foot will be smaller and smaller, then the precision of the welding requirements will be higher. How many lights a square, a lamp has four feet, then a square will have a lot of solder joints, this time, the requirements for the solder joints is very high, then the only solution is to narrow the solder joints. Very small solder stability is very poor, may just touch it, it is possible to fall off, which is SMD can not avoid the problem; COB package eliminates the need for color separation, drying and other processes, the most critical difference is to remove the solder this Process, SMD in the process of solder, the temperature of the control is extremely difficult to grasp, the temperature is too high, will cause damage to the lamp, too low, then the solder is not completely melted. It is easy to cause the Weld, fake welding and so on, for the stability of the lamp beads is a big challenge. And COB does not have this process, then the stability will be greatly improved.
Traditional LED display processing technology is relatively numerous, especially in the process of reflow soldering, high temperature SMD lamp beads and epoxy foam expansion coefficient is not the same, can easily cause the stent and epoxy resin shell fall off, there Gap, in the late use of the gradual emergence of the phenomenon of dead lights, resulting in a higher rate of bad. The reason why the COB display is more stable, because there is no reflow soldering in the processing of welding lights, even if the late reflow soldering IC process, the diode chip has been cured with epoxy resin package to protect, to avoid the welding The machine caused by high temperature solder beads between the beads and the gap between the epoxy resin problems.
COB package challenges
A new product and the emergence of new technology and new technology, never sailing, to research and development and production process constantly testing, try, will find the problem, in order to correct the right medicine to solve the problem. The emergence of each problem, are R & D personnel research process, in this process, full of hardships, but also accompanied by achievements and satisfaction. The development of all new things are a little bit of improvement, but also step by step close to success. But for now, COB packaging technology development can not be called mature, after all, the development of new things still need time to mature. At this stage, COB's packaging technology is also facing some challenges, these challenges, but also in the continuous efforts of enterprises to gradually improve.
It is understood that, at present, COB packaging technology there are still three aspects of the challenge.
1, the packaging process of a pass rate
COB package because of its characteristics, COB package is to be a large board, this board has up to 1024 lights, SMD if the closure of a light, only need to change one on the line, but the COB package 1024 After the completion of the package, to be tested, all the lights to confirm no problem before they can seal. How to ensure that the whole board 1024 lights completely intact, a pass rate is a very big challenge.
2, finished a pass rate
COB product is the first closure of the lamp, after the closure of the lamp, IC drive device to be reflow process, how to ensure that the lamp surface in the reflow treatment, the furnace 240 degrees high temperature does not cause damage to the lamp. This is a big challenge, and SMD compared to the COB to save the lamp surface reflow treatment, but the device surface and SMD, like the need for reflow treatment, that is to say SMD reflow twice, different Is the SMD over reflow when the temperature inside the furnace will cause two kinds of damage to the lamp, one is the wire, the temperature is too high, it will quickly expand rapidly, will cause the filament pull off, the second is The furnace heat through the stent of the four pins quickly passed to the wick, the wick may cause small fragmentation damage, this damage is fatal, detection is often difficult to find, including aging test is also difficult to detect, but The crystal of this tiny damage subtle cracks, after a while
Use, this malpractice will be highlighted, and then lead to lamp failure. And COB is to ensure that the lamp surface after reflow, the furnace does not cause damage to its high temperature, to ensure the yield, which is very important level.
3, the whole lamp maintenance
For the maintenance of COB lights, you need to work together for repair and maintenance. The single lamp maintenance has one of the biggest problems is, after repair, the lights will appear around a circle, repair a lamp, the surrounding circle will be smoked to the gun, maintenance is also relatively high difficulty.
There is a challenge to find the appropriate solution, for now, COB package in the packaging and maintenance process encountered problems, companies have come up with the corresponding solutions, such as in the lamp surface when the reflow, the use of a Way to protect the lamp surface, reduce damage; in the maintenance process using point by point calibration technology to ensure consistency between the lamp beads.