Lamp Beads On The LED Display | Impact Explanation
Lamp beads as the highest cost led display, the largest amount of components, for the quality of led display plays a leading role, so how to identify the merits of led lamp beads?
- Lamp beads why is the most critical components:
①LED is the key device with the largest number of full-color led screen, each square meter will use thousands to tens of thousands of led;
②LED is the main screen that determines the optical display performance of the whole screen, which directly affects the audience’s evaluation of the display;
③LED accounts for the largest proportion of the overall cost of the display, from 30% to 70%.
- How to identify the merits of led display lamp:
① The solder joints: regular led strip manufacturers produce led strips are produced using SMD process, with solder paste and reflow soldering process.
② The quality of FPC: FPC is divided into copper and calendered copper two, copper laying board copper foil is convex, a closer look can be seen from the connection between the pad and FPC.
③ The cleanliness of the led surface: if the SMT process production of led strip, the surface cleanliness is very good, see what impurities and stains.
④ The led lights with the chip and production process: with the eye is not to see the difference, to use aging equipment and testing equipment if you put several manufacturers of led on the aging instrument with high current aging for 24 hours or longer, you then go to measure the brightness of several manufacturers of led, see that led luminous intensity decay the smallest, decay the smallest that the quality is the best.
- What are the effects of lamp beads on led display:
① Perspective: the perspective of the led display is determined by the perspective of the led lamp beads. At present, most of the outdoor displays use the horizontal angle of 100 °, vertical angle of 50 ° elliptical led, indoor display is the choice of horizontal and vertical are 120 ° SMD led. highway display due to its special characteristics of the general choice of 30 ° perspective of the round led.
Some high upstairs display vertical perspective requirements are high. Angle of view and brightness contradict each other, large perspective will certainly reduce the brightness. The angle of view needs to be selected according to the specific use to decide.
② Brightness: led brightness is an important determinant of display brightness. the higher the led brightness, the larger the margin of current used, which is good for saving power consumption and keeping led stable.
LED has different angle values, in the case of chip brightness has been set, the smaller the angle, the brighter the led, but the display perspective is smaller, generally should choose 100 degrees of led to ensure that the display sufficient perspective.
For different point spacing and different view distance of the led display, should find a balance point in the brightness, angle and price.
③ Failure rate: As the full-color display is composed of tens of thousands or even hundreds of thousands of groups of red, green and blue led, the failure of any color led will affect the overall visual effect of the display.
Generally speaking, according to industry experience, the failure rate should not be higher than three ten thousandths of a percent before the led display starts assembling to aging 72 hours for shipment (referring to the failure caused by the led lamp beads themselves).
④ Anti-static ability: led is a semiconductor device, sensitive to static electricity, very easy to cause static failure, so the anti-static ability is critical to the life of the display. Generally speaking, the failure voltage of led’s human electrostatic mode test should not be less than 2000V.
⑤ Life: The theoretical life of led devices is 100,000 hours, much longer than the working life of other components of led display, so as long as the quality of led devices to ensure that the operating current is appropriate, PCB heat dissipation design is reasonable, display production process is rigorous, led devices will be one of the most durable components of the display machine.
LED devices account for 730-0% of the proportion of the price of led display, so that led devices can determine the quality of led display.
The high technical requirements of led display is the future development trend, the high quality requirements of led display, not only about the direction of led display manufacturers, but also implicated in the development of led display device manufacturers.
⑥ Attenuation characteristics: led display will appear after a long period of work brightness decline and display color inconsistency phenomenon, mainly due to the led device brightness attenuation caused by the attenuation of led brightness will cause the display screen brightness reduction.
Red, green, blue led brightness attenuation amplitude inconsistency will cause the led display color inconsistency, we often say that the phenomenon of the display flower. High-quality led devices can well control the brightness decay amplitude.
By 1000 hours of room temperature light 20mA standard, red attenuation should be less than 2%, blue, green attenuation should be less than 10%, so blue, green led in the display design try not to use 20mA current, it is best to use only 70% to 80% of the rated current.
Attenuation characteristics in addition to the red, green, blue led characteristics related to the use of current, PCB board thermal design, the use of the display environment temperature, etc. have an impact on the attenuation.
⑦ Size: the size of the led device affects the pixel distance of the led display, that is, the resolution. 5mm ellipsoidal lights are mainly used for outdoor displays above P16, 3mm ellipsoidal lights are mainly used for P10 outdoor displays, 3528-type SMD led are mainly used for P5, P6 indoor displays, 2020-type SMD led are mainly used for P2, P3 and other indoor displays.
In the premise of the point spacing remains unchanged, led device size increases, can increase the display area, reduce the sense of granularity, however, due to the reduction of the black area, will reduce the contrast; on the contrary, led size decreases, reducing the display area, the sense of granularity increases, the black area increases, increasing the contrast.
⑧ Consistency: The full-color display is composed of countless red, green and blue led spelled out in pixels, and the consistency of brightness and wavelength of each color led determines the brightness consistency, white balance consistency and chromaticity consistency of the whole display.
Generally speaking, display manufacturers require device suppliers to provide led with a wavelength range of 5nm and a brightness range of 1:1.3. These indicators can be reached by device suppliers through the grading of spectrophotometric color separation machines.
Because led is angular, so the full-color led display also has the angle directional, that is, when viewed at different angles, its brightness is increasing or decreasing.
In this way, red, green, blue three color led angle consistency will seriously affect the consistency of different angles of white balance, directly affecting the display video color fidelity.
In short, to achieve red, green, blue three led in different angles when the brightness changes match the consistency, the need for strict scientific design in the package lens design, the choice of raw materials, which depends on the technical level of the package supplier.
The white balance is good display, if the led angle consistency is not good, the white balance effect of the whole screen at different angles will be bad. the angle consistency characteristics of the led beads can be measured by led angle integrated tester, especially important for medium and high-grade display.
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