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Membrane Switches Review and Application

Electronics, Instrumentation & Electrical Database
Membrane Switch Manufacturing and Supply

Membrane Switches Rview and Application

A membrane switch is an electrical switch for turning a circuit on and off. It differs from a mechanical switch, which is usually made of copper and plastic parts: a membrane switch is a circuit printed on PET or ITO. The ink used for screen printing is usually copper / silver / graphite filled and therefore conductive.

Membrane switches are user-equipment interface utilities that allow for the communication of commands from users to electronic devices. Membrane switches can be thought of as one category of interface utilities alongside touch screens, plastic keyboards, toggle switches and many other kinds of control systems. Interface utilities can be as simple as tactile switches for controlling lighting, and they can be as complicated as membrane keyboards and switch panels for use with computers.

Backlighting
There are three standard methods for back lighting membrane switches.

The first option is using Light Emitting Diodes (LEDs) to back light. However, LEDs create bright spots and are not suitable for overall back lighting of a panel, but rather as indicator lights. LEDs can either be surface-mounted to the circuit layer or be placed on a separate LED layer.

A second option is optical fiber. In a typical design, two or more layers of woven fiber-optic cloth are used to form a rectangular light-emitting area. The fibers coming off one end are then bundled into a circular ferrule and coupled to one or more LED light sources. Remote light sources offer 10,000 to 100,000 hours of life. Optical fibers are not affected by extremes in humidity (0% to 100%) or temperature (-40 to +85 deg C).

The third standard option is to use electroluminescent (EL) lamps. They are lower priced compared to fiber optics and offer additional design flexibility. The color of light emitted from an EL lamp can vary depending on the phosphors that are used. Some common colors are blue/green and yellow/green, white, blue and orange. EL lamps have a half life of approximately 3000–8000 hours depending upon the quality of the phosphor. Once they reach their half life, the brightness starts to fade rapidly. EL lamps are thus not a good choice if the lamp is on for an extended period of time. Fading or flashing could double the life of the lamp.

Membrane switches are used in consumer and industrial applications requiring a input pad device. Membrane switches are low cost, considered reliable, and are available in custom or off-the-shelf configurations. By fabrication several layers of polyester (PET) or plastics and onto a printable conductive electronic circuits and a graphic overlay, membrane switches offer product developers a flat keypad type interface system as opposed to classic mechanical type keypads. Membrane switch assemblies are great space and weight savings alternative to mechanical keypads.

Manufacturers and suppliers of membrane switches fabricate assemblies using flexible plastic membrane material , domed or flat mechanical type switch devices and tactile and non-tactile type switches. Membrane switches are used within industry and products for numerical keypads, graphical keypads, keypad control panels, and membrane switch overlays. Below, is a typical membrane switch assembly.

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