The possibility of easy, PWM-based dimming of LEDs is a big advantage compared to
former light sources, but at the same time, it may also result in additional aging
mechanisms compared to continuous DC operation. Due to the different coefficients
of the thermal expansion of each structural layer, temperature cycling can degrade
the main heat conduction path of the LED chips. In this paper, we examine, how the
different dimming frequencies affect the aging of LEDs, and to what extent they impair
the thermal conductivity of structural layers belonging to different thermal time
constants.
