5.9 Reliability and Lifetime
Unlike other light sources, LEDs don‘t “burn out” they just slowly lose their light output over the time. This factor is important in determining the lifespan of LEDs. Manufacturers are now stating lifetime to L70 – 70 % of lumen maintenance. Lifetimes can vary depending on operating conditions (humidity, temperature), current, and type of LED.
There are numerous factors, which can shorten LED lifetime, but the primary cause of lumen decrease is a heat generated by the LED junction. Heat must be removed from the device by conduction or convection. Without sufficient thermal management the device temperature will rise, and high-temperature operation will cause continuous light output decrease.