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Although LED can range from fairly wide channels to obtain supply, but it still need to carefully choose.
Most of the designers that all LED quality are the same. However, numerous LED manufacturer and supplier, Asian producers to the global supply of low cost LED. Surprisingly, in these manufacturer only a few can produce high-quality LED. For just as simple deictic function application, low quality of LED is sufficient to meet the requirements. But in many requires consistency, reliability, solid state indication or lighting and other fields must adopt high quality LED, particularly in harsh environments, such as on the highway, military / aerospace, and industrial applications.
In a New York metro station environment, safety requirements are very harsh, LED must meet the high quality requirements of fundamental factors.
Distinguish between LED quality factor is what? How to tell the difference of two kinds of LED? In fact, selection of high quality LED from chips to start, until the assembly is completed, during which there are many factors to consider. In determining the LED all performance index condition, wafer production technology used by chemical materials are important factors.
A 2 inch wafer can be cut out of more than 6000 LED chip, which only individual chip performance index and different. A good chip manufacturers chip in the color, brightness and voltage drop of the difference is very small. When the LED chip packaging is completed, many of their properties are likely to have very big difference, such as angle of view. In addition, the influence of packaging material also is quite big, for example, silicon resin is better than the performance of epoxy resin.
Classification ability
Excellent LED manufacturers can not only produce high quality chip, but also has according to LED color, brightness, voltage drop and the different perspectives and carries on the classification of packaging capacity. High quality LED suppliers to provide customers with characteristics consistent product quality, and lower LED suppliers can provide similar to" LED.".
For high-end, strict quality requirements of application areas, such as the airport runway edge light, must satisfy the FAA color and brightness of the specification, in order to ensure the performance and security, LED packaging consistency is strictly limited. Packaging class LED was used in demanding applications will lead to premature failure and a series of consistency problem, it is likely to lead to major accidents. In order to avoid equipment downtime and ensure the design specified in the LED has reliable operating characteristic, in the high-end and strict quality requirements of the application to avoid the use of" mixed" products is very important.
Product support capabilities
In addition to the discrete LED, LED assembly and a power supply for its performance, brightness and color indexes have the very important influence. Due to environmental temperature, working current, circuit structure, voltage spikes and environmental factors can affect LED performance indicators, the appropriate circuit design and assembly is to protect LED and ensure the performance of key. LED manufacturers also use various techniques and different material to the design of the circuit structure and assembly, in most cases, the LED assembly experience height difference can cause the same application of LED in the overall performance and reliability of the difference.
With the rapid growth of LED demand, services the global market makers and assembly plant is also increasing rapidly. Unfortunately, a surge in support not only using a large number of low quality LED, their package and LED design engineer experience is also insufficient. Therefore, in addition to the existing experience and accurate screening of LED providers, OEM manufacturers should review their circuit design and assembly techniques to ensure that it meets the design specification, and whether the design provides sufficient cooling capacity, because the resulting LED malfunction and inconsistent performance is the main factor to overheat.
In order to ensure to meet the design requirements, the OEM must be detected LED assembly and circuit structure
Third party testing
In order to eliminate the test in the presence of the injustice, many companies to entrust the third party to test LED assembly and circuit structure. A LED device may be in the harsh environment testing or use of a few weeks. During the test, at the same time pressure, temperature cycle, fixed voltage change, current / fixed / change test, other harsh environmental conditions test to determine if the LED meet the requirements of application. Test before and after a large number of parameters change to be recorded, at the same time to monitor the measured LED brightness, color and the change in voltage drop.
Accelerated life cycle test is a special application areas to avoid the fault of a key test. The test helps to ensure that the screening out those expectations can work at least 100000 hours, but only 1000 hours of work ahead of the failed LED. This is possible, because of the low quality of LED ( may also be assembly design unreasonably high quality LED ) at work 1000 hours after the brightness will be reduced. In fact, a low quality LED if there are higher drive current, early in their careers than high-quality LED more bright, however, excessive current will cause the LED heating too fast, the end result is dimming or burned to the ground.
In addition, assembly technology to some extent effect on the performance of LED than the chip itself is also a great example is some. Design engineer should to LED vendor for the reliability of LED standard, and should be LED assembly tests to ensure the brightness higher is better. Some of the best LED suppliers can ensure that their LED assembly technology reliability can last for three years or longer, and can further provide contains high quality LED and for a special application of appropriate design, final LED product.
The importance of detecting
Two in the field of transport within the application helps to explain adequately tested how to prevent LED in providing high visibility application malfunction. In the early nineteen ninties, LED for car and truck brake lamp. Some of the LED design soon appeared on the performance index of the inconsistency, and quickly destroyed, the reason may be due to LED quality problems, perhaps is the product itself design problems. Until recently, the traffic signal lamp, when LED becomes more suitable light source, this phenomenon was seriously. Design with LED diameter of 8 inch or 12 inch printed circuit board company must choose LED and improve the design and other aspects to consider environmental and application requirements.
Any of the above situation, if the pressure test or accelerated life test have been done, can be considered to be of high quality LED or LED assembly is qualified, it can be applied in the longer service life and higher reliability of the occasion.
Rational use
Not every application needs high quality LED assembly technology. If the LED assembly does not conform to the harsh environmental requirements, the application will not necessarily appear bigger safety risk, or, if the final product repair cost is not very high, the number of assembly technology is perhaps more suitable.
The most fundamental point is LED must be able to afford to buy. Therefore, in the cost limit, we must consider the product packaging grade, assembly design experience and test etc.. To meet the application and market demand of the design is to serve the end users the most effective means of. If the application needs to high-end solutions, then the chip supplier selection, design, and testing are the factors to be considered. If you do not consider the high-end product sales prices, it should be carefully considered discrimination between good and bad LED other related factors. With the packaging grade classification ability of LED suppliers, as well as to reliability, accelerated life cycle testing vendors can be long-term cooperation, which helps manufacturers to adopt a more reliable LED the development of high-end products.