Unlike traditional keypads with moving keys, membrane keypads are pressure sensitive, with key outlines or symbols printed on a flat waterproof surface. A wide variety of products employ membrane keypads, such as remote controls and microwave ovens, printers and switches.
Membrane keypads are a part of many consumer products, but you can also find them in industries where hygiene is important or where systems are exposed to extreme environments. For example, medical technology, the automotive industry and the disposal and recycling industry use membrane keypads.
Membrane keypads consist of four layers. The contact elements for membrane keyboards are embedded between three layers of membrane beneath the waterproof outer layer. The bottom layer is printed with a conductive switch trace for each key. The middle layer, or spacer, has holes exposing each underlying switch. The top layer is a conductive layer with an optional array of rubber domes.
Pressing keys on the outer layer of the membrane keypad completes a circuit. The keys force the conductive layer through the middle spacer so they contact the switch traces on the bottom layer. If rubber domes exist on the top membrane layer, they force pressed keys back into position when released.