Chiclet Keyboard - Design

Design

In some versions of the chiclet keyboard, the bottom three layers are essentially the same as those in the membrane keyboard. In both cases, a keypress is registered when the top layer is forced through a hole to touch the bottom layer. For every key, the conductive traces on the bottom layer are normally separated by a non-conductive gap. Electrical current cannot flow between them; the switch is open. However, when pushed down, conductive material on the underside of the top layer bridges the gap between those traces; the switch is closed, current can flow, and a keypress is registered.

Unlike the membrane keyboard, where the user presses directly onto the top membrane layer, this form of chiclet keyboard places a set of moulded rubber keys above this. With some key designs, the user pushes the key, and under sufficient pressure the thin sides of the rubber key suddenly collapse. In other designs — such as that seen in the diagram — the deliberate weak point is where the key joins the rest of the sheet. The effect is similar in both cases, however.

This collapse allows the solid rubber center to move downwards, forcing the top membrane layer against the bottom layer, and completing the circuit.

The "sudden collapse" of the chiclet keyboard (along with the movement of the key) provides a greater tactile feedback to the user than a simple flat membrane keyboard.

Other versions of the chiclet keyboard omit the upper membrane and hole/spacer layers; instead the underside of the rubber keys themselves have a conductive coating. (This is the type shown in the photograph of the remote control, above). When the key is pushed, the conductive underside makes contact with the traces on the bottom layer, and bridges the gap between them, thus completing the circuit. Grooves between hollow domes on the blue underside permit air to flow out of a dome when a key is pressed, and let air come back in when released.

The dome switch keyboards used with a large proportion of modern PCs are technically similar to chiclet keyboards. However, the rubber keys are replaced with rubber domes, and hard plastic keytops rest on top of these. Because the keytops are wider than the rubber domes the keytops are not separated but align almost perfectly with only a minimal gap in between each other.