Abstract
We develop a light-emitting diode (LED) metal package consisting of
a reflector integrated with a heat spreader as one body. The structure functions
obtained from the thermal transient measurement reveals that the integrated
structure of the metal package leads to improved thermal performance. We make
significant efforts to clarify the interaction between the extracted light
from the LED chip and the inside surface of the metal package. The radiant
flux from the LED chip is calculated from the definition of thermal resistance
and is implemented as an input parameter to predict the optical power and
ray tracing. The simulated optical output power in the far-field mode is 145.3
$~$
mW, which is in
good agreement with the value measured by an integrating sphere. It is shown
that a large portion of the emitted light (37.12 mW) is lost by the interaction
with the package surface before it reaches the far-field receiver. It is demonstrated
that the angle of the first reflector cup is one of the critical design parameters
in the metal package structure that we investigate. When the first reflector
angle is optimized from 80
$^{\circ}$
to 55
$^{\circ}$
(with the second reflector angle of 50
$^{\circ}$
), the optical power increases
from its original value of 145.3–170.15 mW with an improved optical
extraction efficiency from 75.63% to 88.57%. The ray tracing and illuminance
raster charts also confirm that the improved optical performance of the metal
package mainly stems from the optimization of the reflector angles.
© 2013 IEEE
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