Although leds can be bought from a wide range of sources,but its choices still require careful deliberation.
Most designers believe that all led products are of the same quality.However, led manufacturers and suppliers are numerous, with Asian manufacturers supplying low-cost leds to the world.Surprisingly, only a few of these manufacturers can produce high-quality leds. For simple indication applications, low quality leds are sufficient.But in many areas that require consistency, reliability, solid-state indication or lighting, high-quality leds are required, especially in harsh environments such as highways, military/aerospace, and industrial applications, etc.
What are the factors that distinguish led quality?How to tell the difference between two leds? In fact, there are many factors to consider when choosing a high-quality led, starting with the chip and ending with the assembly.Tier-one LED manufacturing company can produce excellent wafers with consistent indicators, which start from high-quality led manufacturing materials and can then produce excellent chips.The chemical material used in the wafer manufacturing process is an important factor in determining all the performance indicators of led.
A 2-inch wafer can cut more than 6,000 LED chips, with only individual chips having different performance indicators.A good chip maker makes chips that vary very little in color, brightness or voltage drop.When the led chip packaging is completed, many of their performance indicators may be very different, such as the beam angle.In addition, the impact of packaging materials is also considerable, for example, silicone resin is better than epoxy resin performance.
Group ability
Good led manufacturers not only make high-quality chips, but also have the ability to classify and package leds according to their color, brightness, voltage drop and Angle of view.High-quality led suppliers will provide customers with products with consistent working characteristics, while lower-quality led suppliers can only provide led similar to “mixed package”.
For high-end applications with strict quality requirements, such as the boundary lights of the airport runway, the color and brightness specifications must meet the FAA level. In order to ensure the performance and safety, the consistency of led packaging is also strictly limited.LED with poor packaging grade is used in the application field with strict requirements, which will lead to a series of non-consistency problems such as premature failure and possibly lead to major accidents.In order to avoid equipment downtime and ensure that the LED specified in the design has reliable working characteristics, it is very important to avoid the use of “mixed” products in high-end and quality demanding applications.
Product supporting capacity
In addition to discrete leds, LED assembly and power supply have a significant impact on performance, brightness, color and other indicators.Because of environmental temperature, working current, circuit structure, voltage spike and environmental factors can affect the performance of LED, appropriate circuit design and assembly is the key to protect LED and ensure performance.LED manufacturers also use a variety of technologies and different materials to design circuit structures and assemblies. In most cases, differences in the experience of LED assemblers will lead to differences in the overall performance and reliability of leds in the same application.
As LED demand has grown rapidly, so has the number of manufacturers and assembly plants serving the global market.Unfortunately, the surge of support manufacturers not only adopt a large number of low-quality LED, their packaging and LED design engineers are also relatively inexperienced.Therefore, in addition to accurately selecting LED suppliers based on existing experience, OEM manufactures must also look at their circuit design and assembly techniques to ensure that the design specifications are met and that the design provides adequate heat dissipation, as the main cause of LED failures and performance inconsistencies is overheating.
To ensure that the design requirements are met, the OEM manufacturers must test the LED assembly and circuit structure
Third party testing
To eliminate injustices in testing, many companies have commissioned third parties to test LED assembly and circuit structures.An LED device may be tested or used for several weeks in harsh conditions.In the process of testing, pressure, temperature cycle, voltage fixed/change, current fixed/change and other tests are conducted at the same time, and other tests under harsh environmental conditions are conducted to determine whether the LED meets the requirements of the application.A large number of parameter changes before and after the test are recorded, and changes in LED brightness, color and voltage drop are monitored.
Accelerated lifecycle testing is a key test to avoid failure in a particular application domain.Testing helps ensure that leds that are expected to work at least 100,000 hours are screened out before they fail after just 1,000 hours.This is possible because low-quality leds (or perhaps higher-quality leds that are improperly assembled and designed) lose their brightness after 1,000 hours of operation.In fact, a low quality LED with a higher driving current will be brighter than a high quality LED at the beginning of operation. However, too high current will make the LED heat too fast, and the final result is dimming or burning.
There are also examples of how assembly technology affects LED performance to some extent more than the chip itself.The design engineer should ask the LED supplier for the reliability specification of the LED, and the LED assembly test should be conducted to ensure that the LED with high brightness is indeed better.Some excellent LED suppliers can guarantee the reliability of their LED assembly technology for three years or longer, and can further provide the final LED products including high-quality LED and appropriate design for specific applications.
Importance of testing
Two applications in the transportation space help explain how adequate testing prevents leds from failing in applications that provide high visibility.In the early 1990s, leds were used in brake lights for cars and trucks.Some LED designs quickly showed inconsistencies in performance indicators and quickly burned down. The reason may be the quality of LED or the design of the product itself.Until recently, when it came to traffic lights, when leds to be a more appropriate source of light, this phenomenon is taken seriously.Companies that design 8 – or 12-inch printed boards full of leds must consider environmental and application requirements in selecting leds and improving designs.
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 the assembly of LED is qualified, and can be applied in situations requiring longer service life and higher reliability.
Intelligent use
Not every application requires high-quality LED assembly technology.If the LED assembly does not meet the requirements of a harsh environment, the application does not necessarily present a significant safety risk, or if the final product is not too costly to maintain it, may be, more appropriate to use a poor assembly technology.
The most important is that leds must be affordable.Therefore, within the cost requirements, it is necessary to consider the supplier’s product packaging level, assembly design experience and testing factors.Design to meet application and market needs is the most effective way to serve the end user.If the application requires high-end solutions, then the selection of chip suppliers, design experience, and testing should be considered.If you don’t consider the selling price of high-end products, you should carefully consider other relevant factors that distinguish good leds from bad ones.LED suppliers with the ability to classify packaging grades, as well as those capable of reliability and accelerated life-cycle testing, can work together for a long time, which will help manufacturers develop high-end products with more reliable leds.
iPHD Lighting Co., Ltd, which professional in research & production & Selling led series light since 2009. We offering outdoor led lighting & indoor led lights, outdoor fixture is included: outdoor wall pack light, led lawn light, led underwater light, led underground light, led floodlight, led wall washer, led street light, swimming led pool light, etc; indoor lamp is included: led track light, led panel light, led down light, etc.
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