These LEDs are just like normal LEDs, except the SMD pads are reversed, allowing you to mount it so the light shines into the PCB. These LEDs are expensive, rare (only three companies make them ...

chances are pretty good that most of us are at least familiar with SMD stencils. These paper-thin laser-cut steel sheets are a handy way to apply a schmear of solder paste to the pads of a PCB ...