From microwaves and washing machines to human machine interfaces (HMIs) and industrial control systems, membrane switches are used in a variety of applications. Not to be confused with a mechanical switch, a membrane switch is a type of electrical switch featuring at least one flexible contact. Some membrane switches have one flexible contact, whereas others have two. Regardless, at least one of the electrical contacts used in their construction is made of a flexible material. Below, you’ll learn more about membrane switches and how they work.
#1) They Feature a Printed Circuit
While there are different types of membrane switches, nearly all of them feature at least a printed circuit. The printed circuit is typically found below the membrane overlay layer, from which it’s separated by a spacer layer. The printed circuit, of course, contains the circuitry needed to control the switch’s circuit. Without this otherwise essential component, a membrane switch wouldn’t function properly.
#2) They Are Resistant to Moisture
Membrane switches are often preferred for outdoor applications over mechanical switches because of their high level of resistance to moisture. They are designed with a sealed construction to protect against the intrusion of moisture or other liquids. Even when used outdoors or in humid environments, a membrane switch shouldn’t suffer moisture damage thanks to its sealed construction.
#3) They Feature Conductive Ink
The printed circuits used in the construction of membrane switches feature conductive ink. Some membrane switches feature copper ink, whereas others have silver or graphite ink. Regardless, the use of conductive ink allows the membrane switch to create a closed circuit when pressed. Pressing the membrane switch causes the underlying conductive traces to make contact with the printed circuit board’s conductive ink, resulting in a closed circuit.
#4) They Can Create Tactile Feedback
Membrane switches are capable of producing tactile feedback. The most common solution for tactile feedback involves adding metal snap domes to the overlay layer. Alternative, the overlay layer can be embossed to create tactile feedback when pressed.
#5) They Support Backlighting
It’s not uncommon for membrane switches to feature backlighting. Light-emitting diodes (LEDs), for instance, are often installed in membrane switches for added illumination. The LEDs can be used either by themselves or in conjunction with light guides. The purpose of light guides is to help distribute the light more evenly across the membrane switch’s overlay layer. In addition to LEDs, other backlighting solutions for membrane switches include fiber optic and electroluminescence (EL).