What is COB? Its full name is chip-on-board, which is a chip-on-board package. It is a new type of package that is different from SMD surface-mount package technology. Specifically, the LED bare chip is adhered to the PCB with conductive or non-conductive glue, and then Wire bonding enables electrical connection and encapsulation of the chip and bond wires with glue.
This kind of packaging is not a package, but integrates upstream and downstream enterprises. The production from LED chip package to LED display unit module or display screen is completed in one factory, which integrates and simplifies the production of packaging companies and display manufacturers. Process, production process is easier to organize and control, product point spacing can be smaller, reliability is multiplied, and cost is closer to civilians.
COB packaging was first used in lighting, and this application has also become a trend. It is understood that COB-packaged bulbs already occupy about 40% of LED bulbs.
As the LED application market matures, users are increasingly demanding product stability and reliability, especially under the same conditions, requiring products to achieve better energy efficiency indicators, lower power consumption, and more competition. Product price. Based on this, compared with the traditional LEDSMD chip package and high power package, the on-chip (COB) integrated package technology directly encapsulates multiple LED chips on a metal-based printed circuit board as a lighting module directly through the substrate. Heat dissipation not only reduces the manufacturing process and cost of the bracket, but also has the advantage of reducing the thermal resistance of the thermal resistance, thus becoming a kind of packaging method that the lighting enterprise mainly pushes.
In addition to good heat dissipation and low cost, COB light source can be customized. However, in terms of technology, COB package still has shortcomings such as light decay, short life, and poor reliability. If it can be solved, it will be one of the leading directions for future package development.
The application of COB in lighting has become a trend and trend. So, can this packaging technology be applied to the display? In terms of packaging methods, some companies have made new attempts, and such attempts have been verified and promoted and applied in the market. At the same time, it has also attracted widespread attention from people in the industry. So, why is the COB display getting everyone's attention? There must be a reason in it.
I. Analysis of advantages and disadvantages of COB packaging
The application of COB package has been applied in the field of lighting for many years. It has many advantages in various aspects, so it has been favored by many lighting companies. So what kind of spark will COB packaging technology use on the display screen? Will there be some levels of acclimatization? Let's analyze the advantages and disadvantages of COB packaging. It is understood that COB packaging technology is applied to the display screen, which has the incomparable advantages of traditional packaging technology.
1. Ultra-thin: According to the actual needs of customers, PCB board with thickness from 0.4-1.2mm can be used to reduce the weight to 1/3 of the original traditional products, which can significantly reduce the structural, transportation and engineering costs for customers.
2. Anti-collision and compression: The COB product directly encapsulates the LED chip in the concave lamp position of the PCB board, and then is encapsulated and cured with epoxy resin glue. The surface of the lamp point is convex into a spherical surface, smooth and hard, and is resistant to collision and wear. .
3. Large viewing angle: The COB package uses shallow well spherical illumination, the viewing angle is greater than 175 degrees, close to 180 degrees, and has a better optical diffuse color glare effect.
4. Bendable: The bendability is unique to the COB package. The bending of the PCB does not cause damage to the packaged LED chip. Therefore, the COB module can be used to easily make LED curved screens, circular screens, and waves. Shape screen. It is an ideal substrate for personalized screens in bars and nightclubs. It can be seamlessly spliced, the production structure is simple, and the price is far lower than the LED shaped screen made by the flexible circuit board and the traditional display module.
5. Strong heat dissipation: COB products are packaged on the PCB board, and the heat of the wick is quickly transmitted through the copper foil on the PCB board, and the copper foil thickness of the PCB board has strict technical requirements, plus immersion gold. The process hardly causes severe light attenuation. Therefore, there are very few dead lights, which greatly extend the life of the LED display.
6, wear-resistant, easy to clean: the surface of the lamp point is convex into a spherical surface, smooth and hard, collision-resistant and wear-resistant; there are dead spots, you can repair point by point; no mask, dust can be cleaned with water or cloth.
7, all-weather excellent characteristics: the use of triple protection treatment, waterproof, moisture, corrosion, dust, static electricity, oxidation, UV effect is outstanding; to meet all-weather working conditions, the temperature difference of minus 30 degrees to zero 80 degrees can still be used normally.
To put it bluntly, the advantages of the COB display package are really quite a lot, especially when compared with the traditional package form, then the contrast effect is more obvious. Since there are many advantages, why not get a large-scale application in the early development of LED display? What are the inadequacies of COB packaging? Hu Zhijun, deputy general manager of Shenzhen Weiqiaoshun Optoelectronics Co., Ltd. said: "The only shortcoming of COB packaging is that the screen ink color is not well controlled. It is the problem of inconsistent surface color when the lamp is not lit." Shenzhen Aoerda Technology Co., Ltd. Yang Rui, the company's marketing director, also said frankly: "The scarcity of the COB display package is that the surface consistency is not enough. If this problem is not solved, it will be difficult to get the customer's approval."
On-Grid Inverter converts DC power to AC power for feeding back to the grid. The frequency of the output voltage of the grid-connected inverter needs to be the same as the grid frequency (50 or 60Hz), which is generally achieved by the oscillator in the machine, and the output voltage will also be limited not to exceed the grid voltage. Modern high-quality grid-connected inverters can have an output power factor of 1, which means that the output voltage and current phases are the same, and the phase difference between them and the grid voltage is within 1 degree. There is a microprocessor in the inverter that can sense the AC waveform of the grid, and according to this waveform, generate voltage and send it back to the grid. However, the electricity sent back to the grid needs to have a certain proportion of reactive power, so that the power of the nearby grid is within the allowable limit. noon) its voltage may rise too high.
If the power of the grid is cut off, the grid-connected inverter needs to be disconnected from the grid quickly. This is a regulation of the National Electrical Code (NEC) in the United States to ensure that when the grid is out of power, the grid-connected inverter will not provide power to the grid, and at this time the workers who maintain the grid will not be electrocuted.
Properly configured, grid-tie inverters allow a home to use alternative energy sources that it generates itself (such as solar or wind power) without cumbersome wiring and without the need for batteries. If there is insufficient alternative energy, the insufficient part will still be provided by electricity from the grid.
Grid-connected inverters are widely used in household photovoltaic power generation systems, commercial and industrial photovoltaic power plants and other scenarios. By connecting to the grid, they help to achieve efficient use of renewable energy and reduce carbon emissions, promoting sustainable development and popularization of clean energy.
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