How innovative LED package technology enables new solid-state lighting designs

October 23, 2017 // By Francois Mirand
The popular high-power LEDs in use today are all formed of three basic elements: a ceramic substrate, generally made of aluminium oxide (also known as alumina) or of aluminium nitride; the LED chip consisting of a die and a phosphor coating affixed on top of the substrate; and an over-moulded silicone lens which encapsulates the LED chip.

An example, the 219C high-power LED from Nichia, is shown in figure 1. Small variations in the design of high-power LEDs can be found between one manufacturer and another, and even between different product families made by a single manufacturer.


Fig. 1: The 219C from Nichia, a high-power lensed
LED (Image credit: Nichia)

Nevertheless, the basic recipe is almost universally followed. This is because it offers numerous advantages.

  • The ceramic substrate is robust and large enough to be easily handled on the production line, and may be assembled on a luminaire’s PCB using a standard surface-mount assembly process.
  • The substrate can accommodate a Zener diode to protect the LED against Electro-Static Discharge (ESD), which may be generated when the device is handled in the factory.
  • The lens protects the chip and any bonding wires.  
  • The lens adapts the refractive index so as to maximise light extraction from the die.
  • Larger ceramic substrates can accommodate multiple LED chips, providing a higher output from a single package.

 

OEMs which use high-power LEDs will be aware of certain drawbacks to this type of device. The substrate gives the device a relatively large board footprint – noticeably larger than the footprint of the chip alone. In addition, the lens has a magnification factor which has the effect of making the light source appear bigger than it really is.

Last but not least, the manufacturing cost of the complex package assembly tends to make the unit cost of a high-power LED higher than that of other LED types.


Vous êtes certain ?

Si vous désactivez les cookies, vous ne pouvez plus naviguer sur le site.

Vous allez être rediriger vers Google.