The most popular is membrane keyad with adhesive layer on the bottom. It can be easily applicable directly on the equipment housing. PCB is based on poliester foil 0,15-0,2mm thick, so the final thickness (including all internal and graphical layers) is very small – min. 0.9mm. The keypad fits to lots of typical housings on the market, where the hollow on the front is usually about 1,0-1,5mm.
The connectors as flexible tapes are possible because of using PET+Cu laminates. It eliminates flat cables (usually soldered manually) and taking lots of area IDC connectors. This solution is very good for big quantities, when the cost of every part is critical. Higher cots of design and prototyping are fast balanced by low cost of production.
The copper based laminate allow to use thinner tracks and it’s important for miniaturization and mounting LEDa by soldering (better quality of connection than condictive glueing).