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Here is a list of some basic LED terms and definitions. 

Bi-Colour LED

Kingbright L-93WEGW Bi-colour Green, Red LED, 617 nm 3-Pin 3mm (T-1), Round Lens Through Hole Package

LED featuring two dies/chips in the same package of different colours.

Bipolar LED

Kingbright L-57IID Red Bipolar LED, 625 nm 5mm (T-1 3/4), Round Lens Through Hole Package

LEDs containing two dies/chips in inverse parallel. The dies/chips can be powered to light one LED or the other depending on the current direction.

Chip-on-Board (COB)

Cree CXB3070-0000-000N0HAB30G, CXA2 White CoB LED, 3000K 80CRI

High-power LEDs consisting of multiple blue LED dies/chips on one array. The chips are then coated with phosphor for a white light output.

Colour bin

Colour binning is the measurement of the LED colour and/or luminosity to separate the same LEDs into classes (bins). It is required to ensure colour or luminosity consistency.

ANSI bin

American National Standards Institute. Binning is the measurement of certain characteristics to separate the LEDs into classes (bins) in a consistent and Industry Standard manner. This allows direct comparison between LEDs from that Manufacturer or any other using ANSI binning.

Colour Rendering Index (CRI)

How well the LED can show the colours of objects in comparison to how they would appear under an ideal light source (daylight). It is a measurement of the quality of light.

Correlated Colour Temperature (CCT)

Nichia NSPW500DS, 500D Series White LED, 5mm (T-1 3/4), Round Lens Through Hole Package

White LEDs are differentiated by their apparent colour temperature. The perceived colour temperature of white light is measured in Kelvin (K).

Die/Chip

The die/chip is what creates the light inside the LED. They are put inside the chosen package to create the LED.

Dominant Wavelength

Kingbright L-53HD, Round Series Red LED, 660 nm 5mm (T-1 3/4), Round Lens Through Hole Package

Wavelength is used to differentiate coloured, UV and IR LEDs. It is measured in nanometres (nm) and is a guide to the perceived colour of an LED. It Is the weighted average of all wavelengths emitted by the LED.

Footprint (SMD)

The base dimensions of the LED that will sit on the PCB. There are many industry-standard sizes, for example 1608 (0603). Written in metric or imperial. There are footprint standards set by JEDEC.

Forward Current

The current required to operate the LED given in milliamps (mA) to produce the specified light output.

Forward Voltage (Vf)

The voltage drop across the operating LED when operated at the defined forward current.

FR-4 Board

Industry standard Glass-reinforced epoxy laminate sheet PCB with electrical insulation. The substrate commonly used for all electronics PCBs. It is also used in low to medium power LED arrays and modules.

IR

Infrared LEDs emit light in the IR spectrum over 800 nm.  Can be used for TV remotes, surveillance etc.

Lens Shape

Ledtech L24S5025K2, LxxS5025K Series Bi-colour Green, Red LED, Rectangular, Rectangle Lens Through Hole Package

Both surface-mounted and through-hole LEDs come with various lens shapes. For example, SMD LEDs with a domed lens and THT LEDs with a round, or square lens.

Lens Colour/Finish

Vishay TLHB5400 Blue LED, 466 nm 5mm (T-1 3/4), Round Lens Through Hole Package

LED packages are clear, diffused and/or tinted which affects their appearance both on and off.

Light Emitting Surface (LES)

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This terminology is used with COB LEDs to describe the area from which the light comes from.

Luminous Flux

Value given in lumens (lm). It is a measure of the light output of an LED.

Luminous Intensity

The measurement of the power of a light source. It is measured in candela (cd).

MacAdam Ellipse

An area on the chromaticity diagram for colours which appear the same as other colours at the centre of the ellipse. The fewer the steps, the less noticeable the difference in colour.

MCPCB

213, 3 cell Colour Mixer MCPCB LED Prototyping Board for Luxeon Rebel LEDs

Metal Core Printed Circuit Board. LEDs are mounted onto this thermally conductive board to produce LED arrays and modules. Also known as IMS (Insulated Metal Substrate) boards. MCPCB/IMS boards provide a short thermal path for High Power LEDs or LED Arrays where a heatsink is necessary. Soldering LEDs to these requires different techniques to FR4.

PC Amber

Cree XPEBPA-L1-0000-00B01, XLamp XP-E2 Series PC Amber LED, 595 nm Clear, Dome Lens SMD Package

Phosphor-Converted Amber. It is a blue light engine that utilises phosphor to create an amber light output.

PCB LED Indicator

Dialight 550-2207F, Green Right Angle PCB LED Indicator, Through Hole 3 V

LEDs mounted within a plastic housing for use as an indicator on a printed circuit board (PCB). The housings are vertical or right-angled and come in various LED colours and arrangements.

Peak Wavelength

The wavelength of highest intensity emitted from the LED.

Remote Phosphor

Intematix ChromaLit Candle 11.9mm Remote Phosphor Lens, 115 °, 3000K, CRI:90

Often in the form of a lens, remote phosphor works with a blue LED (pump) to product a white light output. They have a yellow appearance when not lit.

RGB, RGBW & RGBA LED

Kingbright KAAF-5050RGBS-13 3 RGB LED, 470 / 525 / 625 nm 6-Pin, Round Lens SMD Package

Red, green and blue (RGB) with W (white) or A (amber). These LEDs contain multiple dies/chips, one of each colour, to produce a wide range of different colours.

SMD/SMT

Broadcom HSMG-C170 Green LED, 572 nm 2012 (0805), Rectangle Lens SMD Package

Surface-mounted device / surface mount technology. SMD LED packages are mounted onto the surface of a PCB.

THT

Kingbright L-53ID, Round Series Red LED, 625 nm 5mm (T-1 3/4), Round Lens Through Hole Package

Through-hole technology. THT LEDs have pins which are mounted via holes in the PCB. Standard packages include 3 mm (also known as T-1) and 5 mm (also known as T-1 ¾)

UV

Ultra Violet LEDs emit light in the UV spectrum around 100-400 nm. Can be used for curing, counterfeit detection etc. UV LEDs are available in different forms including UVA, UVB and more recently UVC.

Viewing Angle

The maximum angle at which the LED can be viewed, given in degrees. Sometimes given as a half angle with a ± symbol.

Voltage bin

LEDs can vary in forward voltage during the production process. The voltages are then measured and the LEDs are classed in groups (bins) to help with consistency.

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