Recently my company phased in the metal dome as rubber keypad contact solution. This metal dome solution had been implemented to many cell phone keypad solution also. Better key press feeling, longer life and good reliability is the benefit to use metal dome. As data show the metal dome keypad can sustain 2,000,000 times of finger press verse 300,000 times of poly-dome.
In the beginning we removed the dimple from the metal dome in order to reach higher key press life. Because of the dimple will damage the contact pad the PCB and obtain verdigris from the copper layer base of PCB. The verdigris will finally disconnect the metal dome and contact pad of PCB and result in keypad malfunction.