After the roaring success of its butterfly keyboard design, Apple has an idea to make its laptops even thinnner: attach keys directly to a membrane on the printed circuit board.
In Apple's filing, the company suggests the use of a single membrane sheet adhered directly to the printed circuit board (PCB). A switch housing can optionally be affixed directly to the membrane layer or to the PCB, sandwiched between the two, and a dome switch coupled directly on top to the membrane layer.
Generally the membrane is not typically attached to the PCB, but is used to help facilitate the closing of a connection, to trigger the key press. By attaching the membrane completely across the PCB, this eliminates any wasted space and brings the components closer together.
