Abstract
An investigation of the effects of the optical properties of surface-mount-device (SMD) light-emitting diode (LED) (side-view and top-view LEDs) packaging (PKG) components on the light extraction efficiency ηPKG using ray-tracing simulations is presented. In particular, it is found that the optical properties of the PKG resin and the lead-frame (L/F) silver-plating significantly affect ηPKG. Thus, the effects of the surface reflection methods of these components are investigated in order to optimize the optical design of the LED PKG. It is shown that there exists peak extraction efficiency for each PKG, and the cavity angle formed by the cavity wall is important to the optical design. In addition, the effect of phosphor present in the mold resin is examined using a Mie scattering simulation. Finally, an SMD LED PKG optical design method is proposed on the basis of the simulation results.
Highlights
White surface-mount-device (SMD) light-emitting diodes (LEDs), which are composed of a combination of a blue LED chip and phosphor, are being used for various electronic instruments, and many LED manufacturers and researchers are engaging in intensive competition to further enhance white SMD LED performance.[1,2,3]
We investigate the relationship between the component reflection methods and the ηPKG of the LED PKG using ray-tracing simulations in order to confirm the possibility of optimizing this device
This paper reports on an investigation of the effects of the PKG resin and lead frame (L/F) silver-plating surface reflection methods on the ηPKG values of SVand TV LED PKG using ray-tracing simulations
Summary
White surface-mount-device (SMD) light-emitting diodes (LEDs), which are composed of a combination of a blue LED chip and phosphor, are being used for various electronic instruments, and many LED manufacturers and researchers are engaging in intensive competition to further enhance white SMD LED performance.[1,2,3] improvement of the LED chip output is an important factor in the further development of all LEDs. The optical properties of PKG components are important parameters as regards LED product performance, because an electric input loss of more than 10% is caused by the PKG.[4] In the case of white LEDs, the PKG is composed of various component materials, primarily PKG resin (injection molding resin), mold resin (silicone or epoxy)[9,10,11] containing a phosphor[12,13,14,15,16] and a diffuser material, a lead frame (L/F),[17,18] die-bonding paste,[19,20] and bonding wire.[21,22,23] Each component has been investigated intensively with regard to its performance in each area of the device. Ray-tracing simulations based on the Monte-Carlo method have been used for optical design in the early phase of LED product development.[24,25,26,27] This approach plays an important role in terms of both cost and time reduction. Note that the production of an LED PKG prototype has a high cost and is time consuming, because a die is required
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