LED operating life: durable light quality

The longer a light source is in use, the greater the economic and ecological advantage is. The semiconductor's minimal decrease in luminous flux over the operation period causes the LED to be able to remain in maintenance-free use, in many areas of application, longer than other light sources. The technical potential is still not exhausted by any means. For this reason, the LED represents the future of lighting.


Factors having an influence on reliability and operating life of the individual LED

The operating life (L70B50) of LEDs can easily exceed 50,000 hours. Compared to other light sources, LEDs very rarely fail. Only the luminous flux is slightly reduced over the operating period. In practice, LEDs are virtually service-free during their entire period of use, depending on the particular application. The influential factors on the individual LED, described below, can also affect the entire LED module.


The influential factors in detail

Temperature

When light is produced, heat occurs, which has an effect both on the life cycle and on the LED's luminous flux. This applies to both the individual LED and to an entire LED module. That is why it is essential to divert the heat by the best possible installation method or by suitable heat sinks. The basic principle is as follows: The cooler it is, the longer the LED's life cycle and the more efficient and brighter it is.


Mechanical effect

The causes of the occurrence of mechanical forces can be versatile. This can occur during LED manufacture, assembly or handling and during the use of certain materials which develop mechanical forces during large temperature fluctuations. If a LED is exposed to such forces, this can have a negative effect on its operating life, or can even destroy it


Power consumption

Every LED, and also every LED module, can be operated within a specific current range. The lower the current is within this range, the less energy is released and the lower the heat production is, which has a direct effect on the operating life.


Light

The particular LED's housing design plays an important role in the ageing process of the particular component, influenced by the light emitted by the chip. With many housing designs, the built-in reflector ages a lot in the first few hundred operating hours as a result of the high intensity and luminance of the light emitted by the chip.


Dampness

The LED itself is robust, non-sensitive, vibration-proof and unbreakable. If it is used properly, dampness is also not a problem: as it is not the LED itself but various metal parts, connections and electronic components inside a LED module that are sensitive and may corrode and can thus cause the module to fail. A suitable choice of materials for the LED prevents corrosion. Dampness protection is also absolutely necessary, in order to achieve the highest possible operating life of the LED modules.


Chemicals

Stress to the LED caused by chemical influences can vary greatly depending on the application location. For this reason, all environmental conditions must be taken into consideration when planning an LED lighting system. The following effects, among other things, have a negative effect on the operating life:

  • Corrosive atmosphere (air with high sulfur dioxide content)
  • Coastal climate with medium salt content
  • Chemical industry
  • Swimming pools with medium chloride content

Definition of operating life according to DIN IEC/PAS 62 717:

The operating life of an individual LED module Lx is described as the period during which a LED module delivers more than the specified percentage x of the initial luminous flux, in specified conditions. Example: L70B50 is taken to be the operating life during which the luminous flux is greater than or equal to 70%, for 50% of the population.


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