Capacitive switches have become increasingly popular. Like all switches, they offer an interface for controlling one or more circuits. Capacitive switches are simply touch switches that, like capacitive touchscreens, use capacitance to determine when a circuit should be opened or closed.
When you press your finger against a capacitive switch, you’ll distort its otherwise uniform electrostatic field. The human body is an excellent conductor of electricity. Therefore, touching a capacitive switch with a bare finger will change its electrostatic field. This is essentially how capacitive switches work. Even if you’re familiar with their method of operation, though, you might be wondering what capacitive switches are made of.
All capacitive switches have a circuit layer. The circuit layer, or simply the circuit, is the electrical board that features all of the necessary conductive pathways and transistors. Some capacitive switches have a Flexible Printed (FPC), whereas others have a Printed Circuit Board (PCB). Regardless, they all have a circuit. A circuit is one of several essential parts of a capacitive switch.
In addition to a circuit, all capacitive switches have a backer. The backer, as the name suggests, is the back panel of a capacitive switch. It’s found on the back of the circuit. The purpose of the backer is to create a shell that encloses and protects the circuit. The backer may be joined to a substrate with the use of adhesive. Alternatively, some capacitive switches have a plain backer that’s not joined to a substrate.
The circuit of a capacitive switch is sandwiched between the backer and a top layer known as the overlay. The overlay is the top layer of a capacitive switch. It features the buttons or keys that control the corresponding electrical circuits in the circuit layer below.
Overlays are available in different materials. Some of them are made of plastic or acrylic. Plastic and acrylic are both water resistant and durable, making them popular choices for the overlay. You can also find overlays made of glass. Glass isn’t as durable as plastic or acrylic, but it offers a higher level of optical clarity. Regardless, all capacitive switches have an overlay, which is found on top of the circuit layer.
Capacitive switches are made of several key parts. They contain a circuit layer — the circuit layer may contain multiple individual circuits — as well as a backer layer and an overlay layer.