Membrane switch keys and nomenclature can be backlit using afibre optic layer driven with an LED. The fibre optic backlightingpanel is fabricated from .010 optical fibres applied to areflective backing with a ferrule end tip where the LED isinserted.

A single led is generally sufficient to illuminate up to 40 squareinches. Two or more fibre optic layers, and high power leds can beincluded to increase illumination intensity as appropriate.

Fibre optics are typically applied on top of the metal domes,and directly below the overlay or silicone rubber key pad toachieve maximum illumination. The increase in force needed to closea membrane switch is minimal (5 to 25 grams), and the life of themembrane switch is not affected for most applications. (rated lifeto one million cycles in most circumstances).

Fiber Optic Backlighting