SMD LED (surface mounted device) have no “legs”: they come in a square or rectangular housing with soldering pads, ready to be mounted to PBC or other materials.
This design is commonly found in LED strips and matrix displays, but SMD LED are also available separately or mounted to individual PCB.
Form Factors
SMD LED are classified using a four-digit-code. The code is the size of the LED.
Here are the most common SMD LED types and their sizes:
- 5050: the most common type in *LED strips measures 5.0x5.0mm
- 3535: for narrower *LED strips, the 3535 is used and measures just 3.5x3.5mm. At this size it still has roughly the same capabilities like the 5050
- 2020: if size is crucial, the 2020 needs only 2.0x2.0mm. This miniaturization starts to impact performance, and light emission is typically less (around half) compared to 3535 and 5050.
There are many more sizes and types. The three mentioned are the most common types. 5050 SMD LED are most commonly found on stripes and matrix displays.
Simple LED
Simple SMD LED do not contain any control logic. They are regular LED, just without “legs” and instead with contacts that can be directly soldered to a PCB.
Often, they can be found on breakout boards as simple indicators. They may as well be used in static displays where neither the color nor the pattern changes:
They are also used in LED lamp bulbs and lights:
LED Type
The form factor (like 5050) does not tell what kind of LED is inside, nor does it tell you whether an additional LED controller is embedded, or not.
Most often, though, they contain three or four distinct LED substrates.
Various Color Options
These separated substrates act like individual LED. Vendors can create very bright single colors (by using the same color for all compartments), selectable warm, natural, and/or cold white (by using different white substrates), RGB (by using red, green, and blue substrates), and RGBW (by adding white to red, green and blue).
Since SMD LED types (like 5050) just define a form factor, this does not guarantee any specs or assures any performance. Quality, color stability, and brightness all depend on the specific vendor and the LED substrates that were used inside.
Most vendors produce SMD LED with very similar specs, though. Should you be looking for exceptional above average performance, then ask the vendor for the datasheet so you can look up how well the built-in LEDs perform.
Various Controller Options
Aside from the particular LED substrates, these LED often also embed a LED controller, turning the SMD LED into a programmable SMD LED.
Cheap RGB Stripes use RGB LED without an individual controller. The entire stripe is controlled by one main controller instead, and the stripe can change its color, but only in its entity.
More sophisticated (and expensive) stripes use SMD LED with an embedded controller (such as the WS2812 or similar): each LED can now be individually controlled and is able to play animations or illuminate sophisticated light scenes.
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(content created Mar 18, 2024 - last updated Mar 20, 2024)