Metal Domes
A metal dome is a spherically-formed element used to provide a tactile response in membrane switches. Metal domes are placed on the printed circuit board by means of pressure-sensitive adhesive tape. In their relaxed state, the metal domes rest on the outer rim of the primary pathway. When pushed, the domes collapse and make contact with the secondary pathway, thereby closing the circuit.
There are two ways that metal domes are used. First, metal domes may be placed above the top circuit to actuate the switch as a tactile-only device. Alternately, metal domes can be placed between the top and bottom circuit or above the pad on a single layer switch to actuate the switch as a conductive tactile device. In any application, careful modeling must be used to ensure proper contact on the snap of the dome.
Metal domes are typically made from stainless steel; however, polyester may also be utilized. These domes are commonly referred to as polydomes. Two advantages of
polydomes are that they are not destructive to the substrate and labor involvement is less intensive. Metal domes are available in many different shapes and actuation forces in order to fit specific applications.