Recently, LED displays have become more and more widely used, with good display screens and beautiful colors. However, in practice, we often see some short-term display screens for half a year or after a rainy season. At first, beautiful screens are no longer reproduced. Color distortions, dead lights, large screens, and so on. Professional technicians know this. It must be a device failure or a rust that leads to poor contact. In the field of advertising, LED display is a relatively expensive electronic products, frequently hundreds of thousands, and some even hundreds, tens of millions. So, investing in such a huge equipment, how to guarantee its life span, whether it can maintain a good display effect and a low failure rate during the life cycle, has become a topic of concern for manufacturers and investors alike. Below from the technical point of view, analyze the factors that affect the life of the display, and explore measures to ensure the longevity of the LED display.
1. Factors influencing the life of LED display
The factors influencing the life of LED displays are classified according to internal and external factors, due to the performance of LED light-emitting devices, the performance of peripheral components, and the fatigue resistance of products; externally, there are LED display operating environments.
1.1 Effect of LED Light-emitting Device Performance
LED light-emitting devices are the most critical and most relevant part of the display. For LEDs, we focus on the following indicators: attenuation characteristics, water vapor permeability, and UV resistance.
Luminance decay is an inherent characteristic of LEDs. For a display with a design life of 5 years, if the brightness of the used LED is attenuated by 50% for 5 years, the attenuation margin should be considered at the time of design. Otherwise, the display performance cannot be achieved after 5 years; the stability of the attenuation index is also It is very important that if the attenuation has exceeded 50% in 3 years, it means that the lifetime of this screen is ending prematurely.
The outdoor display screen is often eroded by moisture in the air. The LED light emitting chip may cause stress changes or electrochemical reactions to cause the device to fail when it is exposed to water vapor. Under normal circumstances, the LED light emitting chip is wrapped by the epoxy resin without being eroded, and some LED devices with design defects or material processing defects have poor sealing performance, and water vapor easily passes through the gap of the lead or the gap between the epoxy resin and the casing. Into the device, leading to rapid device failure, the industry called "dead light."
Under the irradiation of ultraviolet rays, the properties of the colloid and the stent material of the LED may change, which may lead to cracking of the device, thereby affecting the lifetime of the LED. Therefore, outdoor LED's UV resistance is also one of the important indicators.
The performance improvement of LED devices requires a process that requires market testing. At present, Japan and some Taiwan-funded enterprises are very cautious and do not promise SMD outdoor waterproofing. Some domestic manufacturers are anxious to launch new products to occupy the market, and in the absence of evaluation, blindly promise outdoor performance. For outdoor SMD5050 display applications, there have been a number of other manufacturers had a lot of quality accidents, and some losses up to tens of millions of dollars, it is shocking.
1.2 Peripheral Component Impact
In addition to LED light-emitting devices, the display also uses many other peripheral components, including circuit boards, plastic housings, switching power supplies, connectors, housings, etc. Any problems with any of the components may result in a reduction in the life of the display. . Therefore, if the maximum life span of the display screen is determined by the lifespan of the key component that is the shortest life, it is not an exaggeration. For example, LEDs, switching power supplies, and metal enclosures are all based on an 8-year standard. The circuit board's protection process performance can only support its work for 2 years. After 2 years, it will be damaged due to corrosion, so we can only get a 2 year warranty. Lifetime display.
1.3 Effect of Anti-Fatigue Performance of the Product
The anti-fatigue performance of display products depends on the production process. The poor anti-fatigue performance of the three anti-handling process is difficult to guarantee. When the temperature and humidity change, cracks will appear on the protective surface of the circuit board, leading to a decrease in protection performance.
Therefore, the production process is also a key factor in determining the life of the display. The production processes involved in the production of display screens include component storage and pretreatment processes, furnace welding processes, three-prevention treatment processes, and waterproof sealing processes. The effectiveness of the process is related to the choice of materials and the ratio of materials, the control of parameters and the quality of the operators. Accumulation of experience is very important. HXTECH LED with many years of experience can control the production process more effectively.
1.4 Impact of the work environment
Due to different uses, the working conditions of the display screen vary widely. From the environmental perspective, the indoor temperature difference is small, no rain and snow and ultraviolet light; outdoor temperature difference of up to 70 degrees, plus wind, sun and rain. The harsh environment will exacerbate the aging of the display. The working environment is an important factor affecting the life of the display.
2. Lifetime protection measures
It can be seen that the lifetime of the LED display is closely related to the use environment. For displays with environmental variables that can be determined, the lifespan can be ensured by selecting the appropriate devices and proper manufacturing processes. This process includes: life design, process control , Reliability verification.
2.1 Life Design
The general design focuses on the realization of functions and the realization of performance indicators. The life design also focuses on the performance indicators after a certain period of time or after a certain number of uses. The output of the design will affect the selection of devices, the selection of production processes, and the selection of verification methods. Only with a full lifespan design, the lifetime of the display screen may be controllable.
2.2 Process Control Focused on Life
Effective design requires an effective process to achieve. In the process of product realization, there are many processes that need process control, including the selection and verification of devices, including the control of the effectiveness of the production process, and are distinguished from the quality control procedures. This control process focuses on long-life.
2.3 High-strength reliability verification
Promoting the use of high-strength reliability verification to ensure that the life of the output of the product is predictable, including verification of raw materials, parts produced during the process, and final verification of the product, is a very important and often overlooked point. We may wish to consider a few questions:
Can the choosed LED be guaranteed for 5 years? Is it promised by the seller or verified by yourself? Is the verification method valid?
Can the circuit board's three-prevention process guarantee 5 years of corrosion protection? Verified? Is the verification method valid?
How does the performance of the shell material change after 5 seasons of spring, summer, autumn and winter? How to verify effectively?
Finding ways to prove effective for 5 years or more is not a simple matter. The methods used by the boeing for spacecraft life control are worth learning. We used high accelerated stress tests [1] to verify high-strength reliability and achieved good results.
Highly accelerated stress tests include high accelerated life testing and high accelerated stress screening. The former aims to make the products and the process of manufacturing the products reach maturity before they are put into mass production, and it is hardly used because of design-induced failures. The purpose of the latter is to eliminate the potential defects of the product and obtain a stable product.
3. Application effect
In practical applications, most of us must complete design-production-delivery tasks in just a few months to meet the individual needs of customers. We have applied effective life-time control methods to a number of large-area landmark displays with an area of over 1,000 square meters. Statistics show that the products are operating stably.