A method for manufacturing a keypad, where the key of the keypad has a key body and a three-dimensional character; the manufacturing method utilizes the female mold corresponding to the key and the male mold having three-dimensional character. The compressor includes a sensorless motor having a rotation shaft connected to a rotator, a piston for performing a compression stroke and an intake stroke between a top dead center and a bottom dead center thereof, and a crank connecting the rotation shaft to the piston. The decarbonating drum rotor is rotated to successively pass through the adsorption region, the desorption region, the purging region, and the regeneration region. The disc including a plurality of openings formed adjacent a periphery of the disc. The second and third insulating films insulate the other portions of the control gates from each other. Advantageously, the performance of the coating is comparable to that of known Cr -based methods for a number of aluminum alloys having particular significance in the manufacture of aircraft.