Light Extraction Improvement for LED COB Devices by Introducing a Patterned Leadframe Substrate Configuration

We propose a patterned leadframe substrate (PLS) configuration for light-emitting diode chip-on-board devices (LED COBs) with regular triangular structures on it. The mechanism of this method is analyzed through ray dynamics, which indicate that the light-propagating regimes are considerably different as the structure inclination angle
$\alpha$
changes. For typical encapsulant materials
$({\rm refractive}~{\rm index}=1.41)$
, the optimal
$\alpha$
is 22.5
$^{\circ}$
–45
$^{\circ}$
. Then the performance of LED COB devices with PLS configurations are verified through 3-D Monte Carlo ray-tracing simulations as well as experimental measurements. Results show that the light-extraction efficiency is significantly improved. A simulated enhancement of 42% and a measured enhancement of 41.07% are observed. These results are in good consistency with the ray dynamic analysis, confirming our predictions about PLS methods. Furthermore, we find that such an LED COB configuration also provides a way to change the angular distribution of intensity from half-peak side angle 101.84
$^{\circ}$
to 141.80
$^{\circ}$
. The findings of our work represent a new concept for LED COB packaging design of great practicality in building lighting systems.