Membrane switches are used in a wide range of electrical applications, including microwave ovens, air conditioners, TV remote controls, massage chairs, dishwashers and more. Unlike a mechanical switch, the circuit of a membrane switch is usually printed on Polyethylene terephthalate (PET) or Indium tin oxide (ITO), with the screen printing ink being copper, silver or graphite.
The purpose of a membrane switch is to allow communication between a user and a device. The user can press various “membrane switches” to issue commands, much like a keypad. In order for it to serve its purpose, though, it must contain a back light mechanism, which is something that we’re going to discuss further in today’s blog post.
Light-emitting diode (LED) – yes, the same LED technology used in TVs and computer monitors – is one option for membrane switch back lighting. The LED bulbs can be installed either directly on the circuit layer, or they can be igven their own dedicated layer. One of the disadvantages of LED back lights for membrane switches, however, is their high level of brightness. This may not cause any issues with certain applications like on/off indicator lights. But for larger applications, it can negatively impact the device’s functionality.
Another back lighting method that’s commonly used in membrane switches is fiber optics. Designs for fiber optic back lights from, with the most basic design consisting of two layers of fiber cloth that are carefully woven together to form a rectangular shape. The fiber materials receive their “light” from a nearby light source, such as a light-emitting diode (LED) bulb. As the light travels from the LED and into the fiber optics, the woven fibers propagate the light to produce illumination for the membrane switch.
Last but not least, electroluminescent (EL) is another viable back light solution for membrane switches. They key advantage of EL is its price. It generally costs less to produce EL back lights as opposed to LED or fiber optics, making it a popular choice among large-scale manufacturers. The EL bulb is also capable of producing light outside the standard “white” range, including blue, green, yellow, and orange colors. Another reason why so many companies prefer EL back lights is their longevity. A typical EL bulb will shine for 3,000-8,000 hours before it begins to fade.