LED strip

An LED strip is a long, narrow circuit board with a row of white LEDs along it, each under a small dome-shaped lens. A TV has several strips running across the back of its backlight; the number of strips and LEDs varies by model.

It starts as a printed circuit board, often with an aluminum or fiberglass base, with copper traces that connect the LEDs in series. Solder paste is printed on the pads, the white LEDs are placed by machine, and the board goes through a reflow oven that melts the solder. Then a lens molded from clear acrylic (PMMA) is glued over each LED. Its shape bends the LED's light outward to the sides, so a few LEDs can light a wide area evenly. A connector at one end plugs the strip into the cable from the power supply board.

In the backlight unit, the strips sit on the floor of the steel chassis, under the reflector and diffuser. Because the LEDs are wired in series, one failed LED can darken a whole strip, or the whole screen. Backlight strips are among the most common reasons LCD TVs fail, often because LEDs driven hard run hot for years.