A keyboard includes a circuit board having an upper surface, a lower surface opposite to the upper surface, and a plurality of cut-out portions, a plurality of key modules positioned on the upper surface and over the plurality of cut-out portions, and a plurality of light sources installed on the lower surface of the circuit board, wherein at least a portion of at least one light source is positioned in a corresponding cut-out portion. Each light source includes a light emitting portion coupled to the second circuit layer. At least some of the light emitting portion is disposed in the cut-out portion beneath and bounded by the key module.