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I am designing a PCB an need an LED on it. I'm going to direct the light from the LED using a light pipe, so I need it to be as bright as possible. The question is what size I should use? All the other components on the PCB are 0805.

Does the brightness of an LED depend on how large the component is? I.e. can I get brighter LEDs if I choose a 1206 footprint? Or are 0805 and 1206 LEDs the same brightness?

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The brightness is not defined by the footprint, but by both what is inside the LED and the lens style.

The data sheet will provide a number of milli-candelas (mcd) for different currents. The data sheet will also provide a viewing profile - a map of how the light is emitted from the LED.

For working with a light pipe you want to be looking for an LED that has as tight a viewing profile as possible so the maximum amount of light is fed up the pipe and not spread around the interior of your unit.

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Depends on the specific manufacturer part. Just because the physical part form factor is bigger doesn't mean its brightest or better. If you look at the datasheet, it will tell you the output. You need to compare the two parts for specifics..

That said, keeping to one form factor size makes it easier to manufacturer and assemble.

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  • \$\begingroup\$ So if the brightness specified in the data sheet is the same for an 0805 and a 1206 then they will be equally bright regardless of the fact that one of the components is larger? \$\endgroup\$ – David Högberg Oct 4 '14 at 7:56
  • \$\begingroup\$ Yes. Keep in mind, that the diode junction size is most likely the same for both, with the bigger one having maybe a slightly bigger lens. \$\endgroup\$ – Passerby Oct 4 '14 at 13:13
  • \$\begingroup\$ The difference between a 1206 and 0805 isn't that big either. \$\endgroup\$ – Passerby Oct 4 '14 at 13:15
  • \$\begingroup\$ @DavidHögberg as a side note, most consumer devices with leds + light pipes? They are using smaller than 0805 leds. Like 0603 or 0402 or even smaller, and they are still obnoxiously bright. \$\endgroup\$ – Passerby Oct 4 '14 at 15:01

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