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Here is a list of some basic LED terms and definitions.Â
LED featuring two dies/chips in the same package of different colours. |
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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. |
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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. |
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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. |
White LEDs are differentiated by their apparent colour temperature. The perceived colour temperature of white light is measured in Kelvin (K). |
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Die/Chip |
The die/chip is what creates the light inside the LED. They are put inside the chosen package to create the LED. |
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. |
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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. |
Infrared LEDs emit light in the IR spectrum over 800 nm. Can be used for TV remotes, surveillance etc. |
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Lens Shape |
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 |
LED packages are clear, diffused and/or tinted which affects their appearance both on and off. |
Light Emitting Surface (LES) |
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 |
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. |
Phosphor-Converted Amber. It is a blue light engine that utilises phosphor to create an amber light output. |
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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. |
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Peak Wavelength |
The wavelength of highest intensity emitted from the LED. |
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. |
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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. |
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Surface-mounted device / surface mount technology. SMD LED packages are mounted onto the surface of a PCB. |
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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) |
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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. |
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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. |