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What is a Surface Mount LED?

Kurt Inman
Kurt Inman

A surface mount LED, also known as an SMD LED, is a light emitting diode which is directly mounted on and soldered to a printed circuit board. Without the leads and surrounding packaging of a standard LED, a surface mount LED is actually quite small, best handled by automated assembly equipment instead of a human. Without the epoxy of a standard light emitting diode enclosure to focus the generated beam, a surface mount LED also has a very wide viewing angle, generally from 100 to 140 degrees.

Like a standard light emitting diode, a surface mount LED gives off almost no heat. It also typically has similar low voltage and low current requirements. They are commonly used to indicate device status on computer motherboards, routers, hard drives, USB flash drives and any other application where physical space is at a premium.

Woman holding a book
Woman holding a book

A surface mount LED is ideal for pushbutton, keyboard or LCD display backlighting, due to its wide viewing angle. They have even been used for custom interior and instrument panel lighting in vehicles. Some manufacturers have created a general-purpose LED lighting solution by combining a surface mount LED, a resistor, a tiny circuit board, a small easily-attachable package with a lens and a few feet of cable. This provides a versatile, cool and bright LED light, which runs on 12 volts DC and is small enough to be mounted just about anywhere, such as to illuminate a car cup holder. Variations include a wide range of colors and multiple light emitting diodes for extra brightness.

On a larger scale, surface mount LEDs are used to create some indoor display screens. Huge numbers of the diodes can be arranged in tight clusters of red, green and blue, so that a variety of colors can easily be generated. The technology in these screens, which may be found in stores and other businesses, is also making its way into much larger outdoor displays.

The term surface mount LED may also refer to a physical package of multiple LEDs, often 10 or more, which is designed to be a replacement for an exterior incandescent bulb-based automotive light. In this case, surface mount reflects the ease of mounting such a light fixture on the surface of a vehicle. This is due to the lighter, flatter enclosure as well as the thin, low-current cables required. Such lights are much more likely to consist of standard LEDs, often with metal reflectors, rather than the surface mount LEDs described above. These bright LED lights are generally used for turn signals, tail lights and brake lights.

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