LIFE-TIME, lumen maintenance and failure rate

The light output of a LED Module decreases over lifetime, this is characterized with the L value. L70 means that the LED module will give 70 % of its initial luminous flux. This value is always related to the number of operation hours and therefore it defines the lifetime of a LED module. The L value is a statistical value, therefore the lumen maintenance may vary over the delivered LED modules. The B value defines the number of modules which are below the specific L value, e.g. L70B10 means 10 % of the LED modules are below 70 % of the initial luminous flux, respectively 90 % will be above 70 % of the initial value. In addition, the failed modules percentage (fatal failure), is characterized by the C value. The F value is the combination of the B and C value. That means that on F degradation and complete failures are considered, e.g. L70F10 means 10 % of the LED modules may fail or be below 70 % of the initial luminous flux