LM-80 is not equal to the life of LED lamps/light bulbs

I. Introduction
At present, LED bulbs have two important problems in the market:
The first is that the logo is unclear. According to the LED bulbs tested by the ITRI, more than 50% of the LED bulbs have an actual luminous flux of less than 10% above the indicated value.
The second is the uneven quality. There is currently no set of specifications on the market that can clarify the relationship between the price and quality of LED bulbs. As consumers often take "apples and oranges" in comparison, some even spend a higher price, but did not buy relatively high quality products, this kind of bad money is getting worse and worse. It has caused the European, American and Japanese countries to pay close attention to the identification and quality of LED lamps/light bulbs.
In view of this, the Energy Bureau of the Ministry of Economic Affairs has also accelerated the promotion of energy-saving stamps for LED bulbs. For this matter, the author is a joy and a worry. The good news is that at least Taiwan has a common standard that can provide consumers with the LED bulbs they need. Worrying, consumers have spent a lot of money and bought LED bulbs that meet the “Energy-Saving Standards Requirements” project. Is there really a guarantee of quality?
Second, the lumen maintenance rate is enough to represent the life of LED lamps?
The more officially representative specifications on the market, which can be related to the life of the bulb, should be the LM-80 specification issued by the US Environmental Protection Agency/Energy Star for LED bulbs/lamps. However, since the release of this specification, there have been some different sounds in North America, and some reliability experts have even begun to call for the immediate stop of the LM-80 lumen maintenance (L70) as the life of LED bulbs or lamps. The only basis for this.
In fact, in 2006, the US Department of Energy's Solid State Lighting (SSL) Quality Working Group invited 32 reliability experts to discuss the reliability and life estimation methods of LEDs in depth. After considering the industrial technology capabilities of LED at that time, the working group decided that the reliability of LED components and lamps with lumen maintenance (L70) would be the most significant and the most easily quantifiable. The reason is that the traditional tungsten filament bulb is used, as long as the tungsten filament is burned, it means that the bulb has reached the end of its life, and the LED bulb is gradually and slowly in the lumen recession. In the early stage of the recession, people are not visually aware. It is always necessary to wait until the light source decays to 70% (L70) of the original light source, and people will feel the light bulb darkening, which will affect the illumination. Therefore, the working group recommended the lumen maintenance rate (L70) as the sole basis for the LM-80 specification. But the controversy is that the lumen maintenance rate is not equal to the life of the LED bulb or the lamp. What are the problems with the LM-80 specification?
Third, Apple wants to compare with Apple: LED lamps are "electronic products", not traditional "light bulbs"
LED component life:
Basically, the LED element is a light emitting diode, which is a kind of electronic component. Therefore, to talk about the life of LED components, you should use the already mature electronic component accelerated life test (ALT) method, with the number of samples and statistical analysis of data to evaluate the life of LED components. In the current LM-80 specification, the three test temperatures, in conjunction with the lumen maintenance rate requirements set by ENERGY STAR, as the failure criteria for LED components, is actually controversial, especially in TM-21 life. After the release of the estimation method, it has solved the situation that each manufacturer talks about the life of LED components. However, for the lighting fixtures using LED components, the possible disputes are:
1. In the ENERGY STAR/LM-80 specification, LED components must be tested at three different temperatures. At each test temperature, at least 20 LED components must pass the 6000-hour test with lumen maintenance. As the sole basis for the success of the test. The controversy is that if there are LED elements that are not lit or burned during the 6000-hour test, they can not be included in the calculation of lumen maintenance. This alone does not meet the requirements for LED component life calculation.
2. It is also feasible to use the LM-80 test data as the basis for life calculation, as long as the failure modes are clearly defined to represent failure (eg lumen maintenance, dead light, burnout, color coordinates / voltage / current bias) Shift, etc.), when the failure mode of any failure definition occurs, it means that the life of the LED component is reached. In addition to the grain quality, including the choice of packaging materials to wire bonding technology, it affects the life and reliability of LED components. Therefore, for LED components to perform LM-80 or life verification, it is absolutely necessary to pass the "reliability verification".
Remarks: In the process of performing LM-80/6000 hours of testing, in order to reduce the risk of partial interruption of the LED, the LED component factory will increase the number of samples tested. When some LEDs appear dead or early in the test. At 夭, ENERGY STAR is a calculation that allows fault samples to be excluded from the average lumen maintenance rate, but the requirements must be noted in the LM-80 report. Therefore, when the luminaire manufacturer reads the LM-80 report provided by the LED supplier, in addition to understanding the test temperature and lumen maintenance rate, the sample quantity information should be more cautious.
LED bulb / lamp life
Does it affect the life of LED bulbs or lamps? Is it really only the factor of lumen maintenance? Basically, LED lamps consist of dimmers, power supplies, light-emitting diodes, optical drive components, and thermal modules. The life of the whole luminaire is actually composed of several electronic modules connected in series or in parallel, and each electronic module has its own function and reliability level. When any module has a problem, it represents the LED luminaire. Invalid, this is very different from traditional tungsten filament bulbs. If we regard LED products as electronic products, what are the main reasons for the failure of LED products?
In fact, from the common failures of general electronic products, you can see one or two. Common failures in electronic products include poor thermal design, overload use, drive circuit failure, power failure, and poor part or process technology. As long as it is a failure that occurs on electronic products, it will basically appear on LED products. For this type of defect, the reliability design verification method of electronic products can usually be used and improved in the laboratory. Another type of failure is a failure in electrical characteristics. For LED lamps, such as lumen maintenance, color temperature/color variation, power supply parameter offset, etc., for this type of defect, use environmental test and reliability proof test. Just verify it. Therefore, from the past experience in the reliability of electronic products, LED products should also follow the traditional electronic product environment and reliability test mode to verify its reliability and longevity.
At present, it is not an easy task to find a large number of LED Lamp failure data in the literature. The relatively large-scale data in the past two years is in Elwood, Pennsylvania, in the eastern United States. Elwood City learned from the 5400 盏 outdoor LED street lamp failure data statistics that the power supply and control drive module failure accounted for 59%, heat dissipation accounted for 31%, LED component defects accounted for about 10%. This is based on the US design and packaging technology capabilities, and for the actual observation of outdoor LED street lights, from the data can be seen that the power module and control drive module accounted for the largest proportion of failure, heat failure caused by failure Second, plus outdoor environmental factors are more complex than indoor environmental factors (including temperature, humidity, rain/condensation, dust, sulphide corrosion, lightning strikes, power supply changes, etc.). Therefore, for outdoor LED products, environmental simulation tests and life tests are more important, not just energy saving or lumen maintenance.

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