A keypad assembly is provided to slim an electronic device by integrally applying hard waveguide layer and contact protrusions to minimize a height of a metal dome and reduce manufacturing cost without an EL(Electro Luminescence) sheet. A keypad assembly(10) is applied as a data input device of an electronic device and includes a substrate(30) and a keypad(20). The substrate has at least one metal dome(31) and at least one LED(Light Emitting Diode)(32) installed in a proper position. The keypad is mounted on the substrate to press the metal domes. The keypad has a key top layer(21) and a waveguide layer(22). The key top layer has a plurality of key tops with engraved characters and numbers. The waveguide layer is laminated under the key top layer to be used as a waveguide device of the LED and has a plurality of contact protrusions(221) on a bottom surface to press the metal domes.
