A LED SMD (acronym of the English Light-Emitting-Diode, Surface-Mount-Device) is a light-emitting diode. They are characterized by having an encapsulation that allows to be welded directly on the surfaces of the printed circuit boards.
The SMD leds are rectangular in shape and consist of one or more cells. These cells contain the light element (semiconductor crystal) that produces light when excited by a direct current.
Single-cell SMD leds can only produce a color or light tone. The SMD leds with three cells contain in each of them a different color where the RGB combination (red, green and blue) is usually used. Thanks to the combination of the three RGB colors you can create light from a range of colors.
To protect the internal circuit of a SMD LED, resins are used that completely cover the dome or upper part of the SMD. These resins for SMD are available in various colors and shades. The LED lens is formed by a transparent resin that protects the light emitting elements.
Depending on the number of cells in the SMD led, it will have a certain number of contacts for welding. One of them is always the anode (+) and the other will be the cathode (-). In the case of a SMD RGB LED it usually has a cathode contact and another anode for each light element. Depending on the manufacturer and the LED specification, the configuration and number of connection points can vary.
Depending on their size, the types of LEDs are classified with a 4-digit number: the first 2 digits for the length and the next 2 for the LED height in tenths of a millimeter. For example, a led 5050 indicates a size of 5x5mm. In the following table we can see the types of smd led most used:
SMD leds are currently the most used type of LED on the market. The large-scale production of large manufacturers has reduced their price significantly. Its development and innovation continues in the light part of the semiconductor crystals offering year after year brighter SMD leds, but with lower consumption. Thanks to this, these LEDs are widely used in domestic and industrial lighting systems, lighting in vehicles, as well as electronic devices of all kinds such as LED screens, televisions, projectors. The SMD leds that combine the RGB system is used for decorative lighting and giant full color image screens.
TV with LED backlight