Most designers believe that the quality of all LED products is the same. However, there are many manufacturers and suppliers of LEDs, and Asian manufacturers supply low-cost LEDs to the world. Surprisingly, only a few of these manufacturers can produce high-quality LEDs. For applications that are only used as a simple indicator, low-quality LEDs are sufficient. However, high-quality LEDs must be used in many fields requiring consistency, reliability, solid-state indication, or lighting, especially in harsh environments, such as highways, military / aerospace, and industrial applications.
Fundamental factor
What are the factors that distinguish the quality of LEDs? How to tell the difference between the two LEDs? In fact, the choice of high-quality LED can start from the chip until the assembly is completed, during which many factors need to be considered. TIer-ONeLED manufacturing company can produce excellent, consistent wafers from high-quality LED manufacturing materials, and then can produce excellent chips. In determining the conditions of all LED performance indicators, the chemical material used in the wafer production process is a very important factor. A 2-inch wafer can cut more than 6,000 LED chips, but only the performance of individual chips is different from the whole. A chip manufactured by an excellent chip manufacturer has very little difference in color, brightness, and voltage drop. When LED chip packaging is completed, many of their performance indicators may be very different, such as viewing angle. In addition, the impact of packaging materials is also quite large, for example, silicone resin has better performance than epoxy resin.
Classification ability
Excellent LED manufacturers can not only manufacture high-quality chips, but also have the ability to classify and package LEDs according to their color, brightness, voltage drop, and viewing angle. High-quality LED suppliers will provide customers with products with consistent operating characteristics, while lower-quality LED suppliers can only provide LEDs similar to "mixed". For high-end, strict quality requirements, such as the boundary lights of airport runways, FAA-level color and brightness specifications must be met. To ensure performance and safety, the consistency of LED packaging is also strictly limited. The use of LEDs with poor packaging grades in demanding applications will lead to a series of inconsistencies such as premature failures, which are likely to cause major accidents. In order to avoid equipment downtime and ensure that the LEDs specified in the design have reliable operating characteristics, it is important to avoid the use of "mixed" products in high-end and strict quality applications.
For high-end, strict quality requirements, such as the boundary lights of airport runways, FAA-level color and brightness specifications must be met. To ensure performance and safety, the consistency of LED packaging is also strictly limited. The use of LEDs with poor packaging grades in demanding applications will lead to a series of inconsistencies such as premature failures, which are likely to cause major accidents. In order to avoid equipment downtime and ensure that the LEDs specified in the design have reliable operating characteristics, it is important to avoid the use of "mixed" products in high-end and strict quality applications.
Product supporting capacity
In addition to discrete LEDs, LED assembly and power supply have a very important impact on its performance, brightness and color. Ambient temperature, operating current, circuit structure, voltage spikes, and environmental factors can all affect LED performance indicators. Proper circuit design and assembly is the key to protecting LEDs and ensuring performance. LED manufacturers also use a variety of technologies and different materials to design circuit structures and assemblies. In most cases, differences in the level of experience of LED assemblers will cause differences in the overall performance and reliability of LEDs in the same application.
With the rapid growth of LED demand, manufacturers and assembly plants serving the global market are also rapidly increasing. It is regrettable that the surge in support manufacturers not only adopted a large number of low-quality LEDs, but also had relatively insufficient experience in packaging and LED design engineers. Therefore, in addition to accurately selecting LED suppliers through existing experience, OEMs must also investigate their circuit design and assembly technology to ensure that they meet the design specifications and whether the design provides sufficient heat dissipation capacity, because it causes LED failure and performance The main factor of inconsistency is overheating.
To ensure that the design requirements are met, the OEM must test the LED assembly and circuit structure
Third-party testing
In order to eliminate the injustice in the test, many companies have commissioned third parties to test the LED assembly and circuit structure. An LED device may be tested or used for several weeks in a harsh environment. During the test, tests such as pressure, temperature cycling, voltage fixation / change, current fixation / change, etc., and other harsh environmental conditions are used to determine whether the LED meets the requirements of the application. A large number of parameter changes that occur before and after the test must be recorded, and at the same time, the changes of the brightness, color and voltage drop of the LED under test must be monitored.
Accelerated life cycle testing is a key test to avoid failures in special applications. The test helps ensure that those LEDs that are expected to work for at least 100,000 hours but fail only in advance of 1,000 hours are selected. This situation may occur because low-quality LEDs (which may also be high-quality LEDs with unreasonable assembly design) will decrease in brightness after 1000 hours of operation. In fact, if a low-quality LED has a higher drive current, it will be brighter than a high-quality LED in the initial stage of operation. However, excessive current will cause the LED to heat up too quickly, and the final result will be dimmed or burned.
In addition, there are also some examples where the assembly technology has a greater impact on LED performance than the chip itself. Design engineers should ask LED suppliers for LED reliability specifications, and LED assembly tests should also be conducted to ensure that higher brightness is indeed better. Some excellent LED suppliers can guarantee the reliability of their LED assembly technology for three years or more, and can further provide final LED products that include high-quality LEDs and appropriate designs for special applications.
The importance of detection
Two applications in the transportation field help explain how adequate testing prevents LEDs from malfunctioning in applications that provide high visibility. In the early 1990s, LEDs were used as brake lights in cars and trucks. Some LED designs soon show inconsistencies in performance indicators and burn out quickly. The reason may be due to the quality of the LED, or it may be entirely a design problem of the product itself. Until recently, this phenomenon was only noticed when LEDs became more suitable light sources for traffic lights. Companies designing 8-inch or 12-inch diameter printed boards covered with LEDs must consider the environment and application requirements in selecting LEDs and improving design.
In any of the above cases, if the stress test or accelerated life cycle test has been done, it can be considered that the high-quality LED or LED assembly is qualified, and it can be applied to those that require longer service life and higher reliability Occasion.
Fair use
Not every application requires high-quality LED assembly technology. If the assembly of the LED does not meet the requirements of the harsh environment, the application will not necessarily present a greater safety risk, or if the maintenance cost of the final product is not very high, it may be more appropriate to use a poorer assembly technology.
The most fundamental point is that the LED must be affordable. Therefore, within the constraints of cost requirements, it is necessary to consider factors such as the packaging level of the supplier's products, experience in assembly design, and testing.
Design that meets application and market needs is the most effective means of serving end users. If the application requires high-end solutions, the choice of chip suppliers, design experience, and testing are all factors that should be considered. If you do not consider the sales price of high-end products, you should carefully consider other relevant factors that distinguish good from bad LEDs. LED suppliers with the ability to classify packaging grades, as well as manufacturers that can perform reliability and accelerated life cycle testing, can cooperate for a long time, which helps manufacturers develop high-end products with more reliable LEDs.
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