Surface mount LEDs

Surface mount devices (SMD) are more common than ever thanks to miniaturization. LEDs inside disk drives, modems, and small personal electronic devices are more often SMD devices these days. Most of the size of a 5mm or 3mm indicator LED is the epoxy package–the actual LED junction is quite small. With SMD LEDs, you don’t get much extra packaging, just the glowing bits. Without the epoxy package focusing the beam, they tend to have wide viewing angles, and are often used with light pipe in a device.

0805 and 0603 SMD white LEDs

SMD LEDs are available in four sizes, which are designated 1206, 0805, 0603 and 0402 . 0402 is the smallest, with overall package size of 1.0 mm x 0.5 mm x 0.45 mm (L x W x H). Then 0603 at 1.6 mm x 0.8 mm x 0.6 mm. 0805 are slightly larger, at 2.0 mm x 1.25 mm x 0.8 mm. 1206 are the big brothers of the family, at 3.2mm x 1.5 mm x 1.1 mm.

0805 and 0603 SMD white LEDs

Electrically, these aren’t very different from the LEDs you’re used to. Both of these are rated for a typical forward current of 35 mA, with a typical forward voltage of 3.6V (4.0V max). Where they stand well apart from the crowd is optically–these are much wider view angle at 140°. The little guy is rated 200 mcd and the 0805 is rated 120. That may seem low if you’re used to specs on 5mm LEDs, but remember that luminous intensity in millicandelas changes as the view angle, so these have a comparable overall flux.

Handling these is difficult. They come in a tape reel packaging designed for automated assembly. Solder reflow is the usual way to connect these to your circuit board, but for home hobbyists with steady hands, a fine-tipped soldering iron may get the job done for you. Be quick–five seconds at 260°C can cook them.

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