Silicone rubber keypads have become an increasingly popular alternative to conventional plastic keypads. Featuring silicone rubber webbing around an electrical switch, they are used to control a circuit. When you press the button, the circuit becomes closed. When you release the button, the circuit reverts back to its open state. In this post, we’re going to explore the basic components of a silicone rubber keypad.
Printed Circuit Board
Found at the base of a silicone rubber keypad is a printed circuit board (PCB). The PCB, of course, is the main circuit board of a typical silicone rubber keypad. It’s responsible for registering when the circuit is open, as well as when it’s closed, and relaying that information to the appropriate device.
In addition to a PCB, silicone rubber keypads also feature a conductive pill. Typically made of either carbon or gold — both of which are highly conductive — the conductive pill is found directly above the PCB. With that said, the conductive pill doesn’t touch the PCB when the silicone rubber keypad’s circuit is open. In its default open state, the silicone rubber keypad has a small amount of space separating the conductive pill from the underlying PCB. The two components only make direct contact with each other when the button is pressed, thus completing the electrical circuit.
Silicone Rubber Webbing
All silicone rubber keypads are made with silicone rubber webbing. After all, silicone rubber webbing is what distinguishes these keypads from other keypads, many of which feature hard plastic instead.
What is the “webbing” of an electrical switch exactly? The webbing is the material that’s placed around the center of the switch. In a silicone rubber keypad, silicone rubber webbing is used. Of course, silicone rubber is an elastic material that’s able to deform when pressed. As a result, pressing a silicone rubber switch’s button causes the webbing to bend down, at which point the conductive pill will touch the PCB to complete the circuit. Releasing the switch’s button, on the other hand, causes the webbing to spring back to its original position.
While not found in all silicone rubber keypads, many of these versatile switching solutions have backlighting. Electroluminescence (EL) or light-emitting diode (LED) backlighting, for example, is often used in conjunction with laser etching. The backlighting is installed underneath the button, after which the top layer of paint is removed from the button using a high-powered laser. The laser essentially burns off some of the paint so that the backlighting can illuminate up and through the silicone rubber keypad.