Membrane switches are designed to serve the same basic function as traditional mechanical switches: to turn on and off devices and perform other operations. The key difference between the two, however, is that traditional mechanical switches are typically made of components containing copper and plastic. In comparison, membrane switches are made with circuits printed on PET or ITO. In order to maintain a high level of conductivity — which is essential for all switches — the membrane switch contains ink that’s either copper, silver or graphite.
Of course, membrane switches are often designed with a back light to provide illumination and improve accuracy. Without a back light, the membrane switch may be difficult to see, let alone use, in low-light conditions. Granted, not all membrane switches will benefit from a back light. If it’s being used outdoors and/or at night, however, a back light will almost certain prove useful.
There are generally three different types of back lights used in membrane switches, each of which has its own unique characteristics. Today we’re going to take a closer look at these back lighting options, revealing which one comes out on top.
One of the three back lighting methods used in membrane switches is light-emitting diodes (LEDs). LEDs are often used as back lighting for indicator lights on membrane switches. They can be mounted to the surface of the circuit layer, or they can installed as a separated layer. Although effective and easy to implement, LEDs have a tendency to create bright sports, restricting their utility as a full-panel back light for membrane switches.
An alternative back lighting option that’s frequently used on membrane switches is optical fiber. Normally, optical fiber back lights consist of at least two layers of woven fiber optic cable to create a rectangular or square-shaped source of illumination. On one of the end of the fiber optics cable, the fibers are grouped together to form a circular ferrule. It is then connected to at least one other LED source. The great thing about optical fiber back lights is their longevity. A standard optical fiber back light can last for 10,000 to 100,000 hours before burning out and needing to be replaced. Furthermore, optical fibers are resistant to moisture and extreme temperatures, offering a functional back lighting option for membrane switches in high-humid or otherwise extreme environments.
The third type of back lighting used in membrane switches is electroluminescent (EL). When compared to the fiber optics, EL backlighting is cheaper and more readily available — and they also support greater freedom of design. You can find EL back lights for membrane switches available in a wide variety of color, ranging from blue and green to yellow, white and orange. This is due to the fact that phosphors are used to create the colors. The color of an EL back light will ultimately depend on the color of the phosphor it uses. While EL back lights may not last for quite as long as optical fiber, they still boast a long lifespan of roughly 3,000 to 8,000 hours.