LED is now the most popular technology for backlight. It makes possible and cheap reaching:
- very high brightness
- easy brightness regulation
- full colours spectrum (RGB)
- very high durability
This kind of key design allow:
- independent steering (key brightness and colour)
- very bright icons (increasing number of LED)
- very high life time (typical gold-plated metal dome)
Placing the PCB deeper into housing (up to 10mm) allow designig keypads for non-flat housings and evently backlighted keys, with big icons or symbols (because of very good light distribution).