US Patent 7435922 Over-molded keypad and method of manufacture

Described is a keypad and its method of manufacture. In one embodiment, a keypad is provided that includes a substrate having a plurality of donut-shaped recesses located at each site of a button for inputting user information, a plurality of cushions each filled with an incompressible fluid (e.g., water), a flex circuit layer, a plurality of metal membranes and an over-molded thermoplastic elastomer layer. During the over-molding of the thermoplastic elastomer layer, the plurality of cushions filled with an incompressible fluid prevents collapse of the space between the flex circuit layer and the plurality of metal membranes. After the layers of the keypad are assembled, the incompressible fluid is removed which leaves a space between the flex circuit layer and the plurality of metal membranes.