Also known as elastomeric keypads, silicone rubber keypads offer a high-performance, low-cost switching solution. Used in consumer and commercial applications alike, they live up to their namesake by featuring a silicone rubber construction. Rather than hard plastic, they contain silicone rubber, which is used as the webbing material for the center switch.
Backlighting
Silicone rubber keypads can be designed with backlighting to create an illuminated, enhanced visual effect. Both electrouminescent (EL) and light-emitting diode (LED) are used as backlighting for silicone rubber keypads.
The EL or LED bulbs work in conjunction with laser etching to illuminate the keypad’s legends. During production, the legends on the top layer of the silicone rubber keypad are etched using a laser, essentially making them transparent. As a result, backlighting like EL or LED will illuminate the keypad’s legends from underneath.
Tactile Feedback
In addition to backlighting, silicone rubber keypads feature tactile feedback. They produce tactile feedback naturally in response to pressing the button. Pressing the button deforms the webbing material so the switch lowers itself onto the contacts below. As the webbing material deforms, it builds force in an effort to “spring” back to its original position. So, when you release your finger from the button, you’ll feel the webbing material as it reverts back to its original position, which is a form of tactile feedback.
Protection From Liquids
Silicone rubber keypads offer a high level of protection against the intrusion of liquids. The silicone rubber material used in their construction is naturally waterproof. Furthermore, there are liquid-resistance standards, such as IP66, used in their design. Standards such as IP66 ensure a high level of protection against water and other liquids that could otherwise contaminate the switch.
PCB
All silicone rubber keypads are designed with a printed circuit board (PCB). The PCB is the main circuitry powering the keypad’s functions. It’s found directly below the switch’s button. The PCB is separated by the switch’s button, however, with a layer of air. This inert layer prevents the switch from activating until the button is pressed.
When you press the button, the webbing material will deform and the bottom of the button — where the contact is located — will press down and against the PCB’s contacts. This completes the electrical switch, essentially activating it. Removing your finger from the button allows the webbing material to “spring” back to its original position and, therefore, pulls the contacts away from each other.
