LED is the abbreviation for "Light Emitting Diode". This is a semiconductor device that emits light when direct current flows through it. The colour of the generated light depends on the structure of the LED chip and the materials used. LEDs are temperature-sensitive dimmable point light sources that emit their light with hemispherical distribution towards the front.
1 Board
2 Heat sink
3 Conversion layer (phosphor)
4 Lens
5 Semiconductor layer
6 Contact wire (bonding wire)
The precise light colour, colour spectrum and luminous efficacy depend on the semiconductor materials and, with white LEDs, on the type and application thickness of the phosphor in the conversion layer. Scattering of the LED properties are unavoidable in the manufacturing process. For this reason, the LEDs are subsequently sorted into bins according to their light colour and other features – also called LED binning.
Pattern of white light colours from warm white to daylight white
Heat dissipation of an LED luminaire via the housing
Module with SMD LED
In the "Surface Mounted Device" (SMD) design, the electronic component, in this case the LED, is soldered directly onto the PCB. The PCB is often a metal core PCB that absorbs and dissipates the heat directly at the LED. The small design enables miniaturised projection optics, very defined light distributions and narrow aperture angles.
SMD LEDs are offered with different spectra, colour temperatures and wattages: High-power and Mid-power LEDs. High-power LEDs usually have a power consumption of 1W or more. Luminaires with Mid-power LEDs have a lower luminance at the light-emitting surface and are therefore particularly suitable for applications where glare control is required.
"Chip-on-board" (COB) technology assembles LED chips without their own housing directly on the PCB. The chip is encapsulated to protect against external influences. For lighting purposes, these LED designs are often used together with reflectors. The diameter of the luminous surface (LES: Light Emitting Surface) of a COB is a characterising property.
