Editing Membrane keyboard (section)

==Description==
Membrane keyboards use plastic sheets for the matrix traces. This is a cost-effective alternative to printed circuit boards. Exposed pads within these traces allow for switching. A conductive object can be placed between the pads to bridge the gap, or pads on separate layers can be brought together under pressure given that the membrane sheets are highly flexible.

Examination of one keyboard showed that the top and bottom membranes are around 0.06 mm thick, while the centre spacer layer is around 0.09 mm thick. This is around the same thickness as 80 gsm paper.

The membrane layers must be kept flat; traditionally they are backed by a backplane of steel but in cheaper constructions the rear case will support the membranes directly.
Because membranes are flexible the backplanes can be [[Keyboard profile#Curved backplane|curved]] or consist of multiple parts at different angles and/or heights with a single membrane/stack. Extensions of membranes are sometimes used as ribbon cables connecting the matrix traces to the [[keyboard controller]].