Switches are found in nearly all electronic devices. Whether it’s a computer, automotive navigation system or even a digital watch, most electronic devices contain one or more switches. A switch is simply a component that controls the path of conductivity in an electrical circuit. A switch can be open, in which case the circuit will break, or it can be closed, in which case the circuit will complete. While all switches follow this same basic design, membrane switches have a unique construction that distinguishes them from all other switching solutions.
An Introduction to Membrane Switches
A membrane switch is a type of switch that features a flexible, semi-elastic construction. According to the ASTM, any switch that features at least one contact made of a flexible material is considered a membrane switch.
Like most other switches, membrane switches feature two conductive contacts. There’s a top contact embedded underneath the switch’s button, followed by a bottom contact. Between these two contacts is a layer of air. Pressing the button will push the top contact into the bottom contact, resulting in the completion of the circuit. Membrane switches are unique because they contain flexible and semi-elastic material around one or both of these contact contacts.
Taking a Closer Look at How Membrane Switches Work
As previously mentioned, the inner-workings of membrane switches relies on a simple circuit mechanism. A membrane switch has an open circuit in its default state. When pressed, the circuit closes.
Most membrane switches are comprised of layers. At the top, there’s an overlay layer featuring the button as well as a conductive contact. Below the overlay layer is a space layer that’s filled with air. Next, there’s a printed circuit layer that features a second conductive contact, followed by adhesive and fail filler.
Why Membrane Switches Are a Popular Alternative to Plastic Switches
Although there are plenty of plastic switches on the market, membrane switches have become a popular alternative in recent years. The flexible materials used in their construction have strong waterproof propertites. Therefore, membrane switches can be used in harsh environments, such as the outdoors, where moisture is a concern.
Membrane switches can also be enhanced using backlighting. They support many forms of backlighting, some of which include light-emitting diode (LED), electroluminescent (EL) and fiber optic. Backlighting is embedded in the rear of the membrane switch where it’s able to project illumination up through the overlay layer.