As the most expensive and largest amount part of full color led display, led lamps play a decisive role to the led display quality. Now Optokingdom will show you how to tell if the led lamps which are the key component of led display is good or not. (Optokingdom is an online shopping mall created by Haisheng LED Co., Ltd aimed at providing led display and relevant accessories products and services.) 

There are three reasons making led lamps to be the key component of full color led display:

First, led lamps are the key apparatus of full color led display because of its large amount. The chips density can be thousands to tens of thousands pieces per square meter.

Second, led lamps are the main subjects to determine the optical display performance of the whole screen. It directly affects the evaluation of audience to the display.

Third, the cost for led lamps is the largest part of the led display costs, the range can be from 30% to 70%.

How to tell if the LED lamps are good or not?

First, check the solder joints. Regular led lamp belt manufacturers use SMT process, solder paste and reflow-soldering process processes to produce led lamp belt.

Second, check the FPC quality. FPC are divided into apply copper and rolled copper. The copper foil for apply copper is stick out, it can be observed if see through the joint of welding plate and FPC.

Third, check the cleanliness of the led lamp surface. Led lamp belt with SMT process will have very nice cleanliness, no impurities and stain on it.

Fourth, check the chips and production process of the led lamps. You have to use aging test equipments to distinguish such items because it’s impossible to tell by eyes. You can light led lamps from different companies on the aging test equipments for at least 24h, then measure the brightness of the led lamps, the led lamps which has the minimum attenuation in luminous intensity has the best quality.

The influences of the led lamps to led display

1.View angle

The led display view angle is based on the view angle of led lamps. At present most of the outdoor led display are using elliptic led lamps with horizontal view angle 100°and vertical view angle 50° while indoor led display are using SMD led with horizontal view angle 120°and vertical view angle 120°. The display along high way usually select rounded led lamps with 30°view angle because of its particularity. The led display on tall buildings has higher standard to vertical view angle. The view angle and brightness are not in direct proportion, large view angle means less luminance, so the selection of the view angle depends on the usage of the led display.

2.luminance

LED luminance is the major determinant of the display brightness. Larger led luminance means more current allowance, it has benefits for energy saving and maintaining stable performance of led lamps.LED lamps have various view angle, for a certain chip luminance, the smaller view angle makes the led lamps more bright but the led display will have small view angle. Usually 100°view angle is enough to maintain good view effect to a display. Customers can find a balance between the luminance, view angle and price according the pixel pitch and view distance of the led display.

3. Malfunction Dot Rate

Because full color led display has large amounts of pixels which consist tens thousands or even hundreds thousands of R, G, B led lamps, the malfunction to any led lamps will make a big effect to the whole view effect of the display. In general, the industry experience shows that the malfunction dot rate for led display which is caused by the led lamp quality problems should be less than 0.03% during the 72 aging period from the beginning of assembling to pre-delivery.

4.Antistatic ability

LED is semiconductor apparatus, antistatic ability is very important to its lifespan because it is sensitive to electrostatic and easy to get static electricity failure. Generally speaking, the failure voltage of human body electrostatic mode test on LED should not be less than 2000V.

5. lifespan

The theory lifespan of led apparatus can be more than hundred thousand hours, it’s far more longer than the lifetime of all other parts of led display, thus if the led apparatus has good quality with rigorous production process and works with suitable current and with reasonable heat emission design to PCB, the LED apparatus is one of the most durable components on led display.

6. attenuation characteristics

The phenomenon that screen brightness is reduced and color is not consistent will occur when the led display works for a long time, that’s caused by the led attenuation characteristics. The different luminance attenuation amplitude on the red, green and yellow led chips will cause the color inconsistent on the display screen. The phenomenon is called screen crash. High quality LED apparatus can effectively control brightness attenuation amplitude. Under the standard that led is lit up for 1000 hours with 20 mA current in room temperature, attenuation on red color should be less than 2% while attenuation on blue and green color should be less than 10%. Thus when design the led displays, don’t use 20 mA for blue and green led lamps, it’s better to use only 70% to 80% of the rated current.

Not only the characteristics of red, green and blue led lamps will affect the display attenuation characteristics, but also the working current, heat emission design on PCB and the temperature of the working environment will have influence to the display attenuation characteristics.

7.dimensions

The dimensions of the led apparatus will affect the pixel pitch of the led display, (i.e., the resolution). The 5mm elliptical lamps are mainly used for outdoor p16 or above led display; 3mm elliptical lamps are mainly used for p10, p12, p12.5 outdoor led display; 3528 SMD led are mainly used for p6, p8 indoor led display; 2020 SMD led are mainly used for p2, p3 indoor led display. Under the premise of a certain pixel pitch, the increased dimension of the led apparatus will increase the display area and reduce the sense of particles, and at the same time the decreased dark area will reduce the contrast; similarly, the decreased dimension of the led apparatus will reduce the display area and increase the sense of particles, and the increased dark area will increase the contrast.

8. Consistency

Full color led display screen is made of numerous pixels which consist of red, green, blue led lamps, the consistency of brightness and wavelength of each led color will decide the brightness consistency, white balance consistency and color consistency of the whole screen. Generally speaking, led display manufacturers will ask the led apparatus suppliers to provide led lamps that has 5 nm wavelength and 1:1.3 brightness range. The led apparatus suppliers can achieve these characteristics by means of classify the led apparatus via sorting machines, but no requirements on the voltage consistency.

Full color led display has view angle limitation due to the view angle of the led lamps, i.e. in different view angles, its luminance will increase or decrease. In this way the view angle consistency of the red, green, blue led lamps will have a strong impact on the white balance consistency in different view angles so as to affect the video color fidelity of the display. In order to match brightness consistence on the red, green, blue led color when they are changing in various view angles, it needs rigorous scientific design on the encapsulated lens design and raw material selection. This depends on the technology level of the packaging suppliers. The display with good white balance in normal direction won’t have good white balance effect in various view angles if the led lamps don’t have good view angle consistency. The view angle consistency of led lamps is very important for the medium and top grade led display, and it can be detected by LED Angle comprehensive tester.

In conclusion, a good quality led display must have top quality led lamps. As an online shopping mall for providing led display and relative accessory products and service to customers, all the led display, led module and led lamps on optokingdom are provided by the best raw material suppliers, led lamps supplier and led packaging manufactures.