High power light emitting diodes (LEDs) are much more efficient than conventional light sources like filament bulbs. Nevertheless, heat is still generated, and this directly affects the reliability of these solid-state light (SSL) devices.

In order to decrease the operating temperature, these LEDs
can be assembled on metal core printed circuit boards
(MCPCBs). However, in applications where stability/lifetime is
a critical parameter, such as space applications, diamond
plates may be considered. These plates are available from
manufacturers with metallized tracks for direct assemblage of
surface mount devices (SMD). In order to evaluate the impact
of the board on SSL reliability, high power Cree LEDs were
assembled on MCPCB and diamond plates. The case tempera
ture was measured for different current ratings and the life
time increase induced by the diamond plate was estimated
based on the calculation of the acceleration factor (AF).

Diamond plates were shown to have a big impact on the life
time; for nominal current level, and depending on the active
tion energy of the aging processes, the LED assembled on the
MCPCB will age 2.5-8.8 times faster than the one assembled on
the diamond plate. For high current ratings the spectrum
radiated by the LED assembled on the diamond plate was also
shown to be more stable than the one on the MCPCB.