The harm of high temperature to LED display_full color LED display|led display manufacturer|Huaze Optoelectronics

The LED display screen is very picky about the ambient temperature. Theoretically, the room temperature is about 25 degrees Celsius, and its working condition is ideal. But in fact, the ambient temperature in the application of outdoor LED displays is quite complicated. The maximum temperature in summer may be above 60 degrees Celsius, and the minimum temperature in winter may be below -20 degrees Celsius. The working efficiency and performance of LED and IC are inconsistent, the brightness will be inconsistent, and the overall display of the screen will naturally change. Under different temperature conditions, the brightness attenuation and decline of the red, green and blue lights are different. At 25 degrees Celsius, the white balance is normal, but the brightness of the three colors decreases at 60 degrees Celsius. , And its attenuation values u200bu200bare inconsistent, so the entire screen brightness and color cast will occur, and the quality of the entire screen will decrease. 1. Excessive temperature will lead to the complete destruction of the LED display (1) The working temperature of the LED display exceeds the carrying temperature of the chip, which will rapidly reduce the luminous efficiency of the LED display, causing obvious light decay and causing damage; (2) ) LED displays are mostly encapsulated with transparent epoxy resin. If the junction temperature exceeds the solid phase transition temperature (usually 125°C), the packaging material will transform into rubber and the thermal expansion coefficient will rise sharply, which will cause the LED display to open and fail. Second, the temperature rise will shorten the life of the LED display. The life of the LED display is manifested by its light decay, that is, as the time is longer, the brightness will become lower and lower until it is finally extinguished. It is generally defined that the time when the luminous flux of the led display screen decays by 30 is its life. Generally, the reasons for the light decay of LED display screens are as follows: (1) The defects in the LED display chip material will rapidly multiply and multiply at higher temperatures, until they invade the light-emitting area and form a large number of non-radiative composite centers. Seriously reduce the luminous efficiency of the led display. In addition, under high temperature conditions, micro-defects in the material and fast-expanding impurities from the interface and the electric plate will also be introduced into the light-emitting area, forming a large number of deep energy levels, which will also accelerate the light decay of the LED display device. (2) High temperature When the transparent epoxy resin will denature and turn yellow, it will affect its light transmission performance. The higher the working temperature, the faster this process will proceed. This is another main reason for the light decay of the LED display. (3) The light decay of phosphors is also a main reason that affects the light decay of LED displays, because the attenuation of phosphors is very serious at high temperatures. Therefore, high temperature is the main source of LED display light decay and shortening the life of the LED display. The light attenuation of different brands of LED displays is different, usually led display manufacturers will give a set of standard light attenuation curve. The attenuation of the luminous flux of the LED display screen caused by high temperature is unrecoverable. The luminous flux before the unrecoverable light attenuation of the LED display screen is called the 'initial luminous flux' of the LED display screen. 3. Temperature increase will reduce the luminous efficiency of the LED display. The reasons why temperature affects the luminous efficiency of the LED display include the following aspects: (1) When the temperature of the LED display rises, the concentration of electrons and holes will increase, and the band gap width Will decrease, and the electron mobility will decrease. (2) As the temperature of the LED display increases, the probability of radiative recombination of electrons and holes in the potential well decreases, resulting in non-radiative recombination (heat generation), thereby reducing the internal quantum efficiency of the LED display. (3) The increase in the temperature of the LED display causes the blue peak of the chip to shift to the long wave direction, which makes the emission wavelength of the chip and the excitation wavelength of the phosphor not match, and also causes the reduction of the external light extraction efficiency of the white light LED display. (4) As the temperature of the LED display increases, the quantum efficiency of the phosphor decreases, the light emission decreases, and the external light extraction efficiency of the LED display decreases. (5) The performance of silica gel is greatly affected by ambient temperature. As the temperature increases, the thermal stress inside the silica gel increases, resulting in a decrease in the refractive index of the silica gel, which affects the light efficiency of the LED display. Fourth, the influence of temperature on the luminous wavelength (light color) of the LED display The luminous wavelength of the LED display can generally be divided into the peak wavelength and the dominant wavelength. The peak wavelength is the wavelength with the maximum light intensity, and the dominant wavelength can be determined by the X and Y chromaticity coordinates, reflecting the color perceived by the human eye. Obviously, the change in the light-emitting wavelength of the led display screen caused by the junction temperature will directly cause the human eyes to have different perceptions of the light-emitting color of the led display screen. For an LED display device, the band gap value of the material in the luminescent zone directly determines the wavelength or color of the device's light emission. As the temperature rises, the band gap of the material will decrease, which will cause the device to emit longer wavelengths and red shift the color. 5. Excessive temperature will limit the maximum injection current of the LED display. The above points are the introduction of the influence of temperature on the LED display. Through the above introduction, it is known that the influence of temperature rise on the LED display is very huge. So the right and right temperature is the focus of the LED display.