What are the effects of LED lamp beads on LED displays?
As the LED LED display with the highest cost and the largest amount of components, LED lamp beads play a leading role in the quality of LED display. Today we will introduce to you why the LED lamp bead is the most critical component of the LED display. How to identify the advantages and disadvantages of the LED lamp bead?
The most critical component of a full-color LED display is the LED lamp bead. There are three reasons:
First, LED is the most used key component in the full-color screen, using thousands to tens of thousands of LEDs per square meter;
Second, the LED is the main body that determines the optical display performance of the whole screen, directly affecting the audience's evaluation of the display screen;
Third, LEDs account for the largest proportion of the overall cost of the display, ranging from 30% to 70%.
How to identify the advantages and disadvantages of LED display beads
First, look at the solder joints. The LED strips produced by the regular LED strips are made by SMT chip process, solder paste and reflow soldering process.
Second, look at the quality of FPC. FPC is divided into copper and rolled copper. The copper foil of the copper plate is convex. If you look at it, you can see it from the connection between the pad and the FPC.
Third, look at the cleanliness of the surface of the LED light strip. If the LED strip produced by the SMT process has a very clean surface, no impurities or stains can be seen.
Fourth, look at the chip and production process of LED lights, the eyes can not see the difference, to use aging equipment and testing equipment, if you put several manufacturers of LEDs on the aging instrument with high current aging for 24 hours or longer Time, you then measure the LED brightness of several manufacturers, see that the LED luminous intensity attenuation is the smallest, the attenuation is the best.
What are the effects of LED lamp beads on LED displays?
The viewing angle of the LED display is determined by the viewing angle of the LED bead. At present, LED outdoor display screens mostly use a horizontal viewing angle of 100°; a vertical viewing angle of 50°; an elliptical LED, and an indoor display screen that uses a horizontal and vertical 120°; The display on the highway is generally 30° due to its particularity; a circular LED with a viewing angle is sufficient. Some high-rise buildings require a higher vertical viewing angle. The angle of view and brightness are contradictory, and a large angle of view necessarily reduces brightness. The choice of perspective needs to be determined based on the specific application.
LED brightness is an important determinant of display brightness. The higher the brightness of the LED, the larger the margin of current used, which is beneficial for saving power and keeping the LED stable. LEDs have different angle values. When the brightness of the chip is fixed, the smaller the angle, the brighter the LED, but the smaller the viewing angle of the display. Generally, a 100 degree LED should be selected to ensure a sufficient viewing angle of the display. For displays with different dot pitches and different line of sight, a balance should be found in brightness, angle and price.
3, failure rate
Since the LED full-color display is composed of tens of thousands or even hundreds of thousands of red, green and blue LEDs, the failure of any color LED will affect the overall visual effect of the display. In general, according to industry experience, the failure rate before the LED display starts to assemble to aging 72 hours before shipment should be no more than three ten thousandth (refer to the failure caused by the LED lamp itself).
4, antistatic ability
LEDs are semiconductor devices that are sensitive to static electricity and can easily cause electrostatic failure. Therefore, antistatic capability is critical to the life of the display. In general, the LED's human body static mode test failure voltage should not be lower than 2000V.
The theoretical life of the LED device is 100,000 hours, which is much larger than the working life of other components of the LED display. Therefore, as long as the LED device quality is guaranteed, the working current is suitable, the PCB heat dissipation design is reasonable, and the display production process is rigorous, the LED device will be the display screen. One of the most durable parts in the machine.
LED devices account for 70% of the price of LED displays, so LED devices can determine the quality of LED displays. China is a big country in the production of LED devices, and it is also a gathering place for LED display. The high technical requirements of LED display is the future development trend. The high quality requirements of LED display are not only related to the trend of LED display manufacturers, but also the development of LED display device manufacturers. From the LED device check, promote China's transformation from a large LED display manufacturing country to a LED display manufacturing power.
6, attenuation characteristics
When the LED display is operated for a long time, the brightness will drop and the color of the display will be inconsistent, mainly due to the brightness decay of the LED device. Attenuation of the brightness of the LED will cause the brightness of the entire screen of the display to decrease. Inconsistent brightness attenuation of red, green and blue LEDs will cause inconsistencies in the color of the LED display, which is what we often say about the display. High quality LED devices provide excellent control of the brightness attenuation. According to 1000 hours of normal temperature lighting 20mA standard, red attenuation should be less than 2%, blue and green attenuation should be less than 10%, so blue and green LEDs should not use 20mA current in the display design, preferably only 70% to 80% % rated current.
In addition to the characteristics of the red, green and blue LEDs, the attenuation characteristics are affected by the current, the heat dissipation design of the PCB, and the ambient temperature of the display.
The size of the LED device affects the pixel point distance of the LED display, ie the resolution. The 5mm elliptical lamp is mainly used for outdoor display above P16, the 3mm elliptical lamp is mainly used for outdoor display of P12.5, P12 and P10, and the 3528 type patch LED is mainly used for indoor display of P6 and P8. 2020 type SMD LED is mainly used for indoor display such as P2 and P3. Under the premise of constant dot pitch, the LED device size increases, which can increase the display area and reduce the graininess. However, due to the reduction of the black area, the contrast will be reduced. On the contrary, the LED size is reduced, the display area is reduced, and the graininess is increased. The area of the black area increases and the contrast is increased.
LED full color display is composed of countless red, green and blue LEDs. The brightness and wavelength consistency of each color LED determine the brightness consistency, white balance consistency and chroma of the entire display. consistency. In general, display manufacturers require device vendors to provide LEDs with a wavelength range of 5 nm and a brightness range of 1:1.3. These specifications can be achieved by device suppliers through a spectral color separation machine. The consistency of the voltage is generally not required.
Since the LEDs are angled, the full-color LED display also has angular orientation, that is, the brightness is increased or decreased when viewed at different angles. In this way, the angular consistency of the red, green, and blue LEDs will seriously affect the consistency of white balance at different angles, directly affecting the fidelity of the display video color. To achieve the consistency of the brightness changes of the red, green and blue LEDs at different angles, it is necessary to strictly carry out scientific design on the packaging lens design and raw material selection, depending on the technical level of the packaging supplier. In the normal direction, the white balance is good. If the angle of the LED is not consistent, the white balance effect at different angles of the whole screen will be bad. The angle uniformity of the LED lamp bead can be measured by the LED angle comprehensive tester, which is especially important for medium and high-end displays.