Low profile microswitches, particularly useful for the composition of keyboards and method of making

DETAILED DESCRIPTION We claim: 1.
A low profile microswitch particularly useful for keyboards of the kind having an electrically conductive movable contact spherical cap member able to invert its sense of curvature with the application of pressure thereon, characterized in that a first generally annular contact is disposed on a generally planar surface on an insulating substrate arranged for contacting the peripheral area of said cap member; at least three protuberances are formed in the substrate extending above said generally planar surface spaced about each microswitch and adjacent thereto to laterally center the cap member in registry with the annular contact; and a second contact is disposed as a button substantially at the center of said first contact and in such a way so as to be electrically isolated from the first contact.
2.
A microswitch according to claim 1, characterized in the substrate is deformed so as to obtain a lowered channel passing under the external periphery of said cap member for realizing an air vent and a passage for conducting traces.
3.
A microswitch according to claim 1 characterized in that said contacts are realized by means of the techniques utilized for printed circuits.
4.
A microswitch according to claim 1 characterized in that said substrate is constituted by a panel of fibers bonded with a resin.
5.
A low profile keyboard comprising an electrically insulative substrate having generally flat top and bottom planar surfaces, a plurality of microswitches formed on the board each comprising a first conductive contact surface disposed on the flat top planar surface, a plurality of spherical cap centering portions spaced about the periphery of a selected circular configuration on the substrate aligned with the first contact surface, the portions each formed of a protuberance extending from the top surface of the substrate and an aligned depression in the bottom surface of the substrate, a second conductive contact surface disposed on the flat top planar surface within the said periphery but electrically separated from the first conductive contact surface and an electrically conductive spherical cap able to invert its sense of curvature with the application of pressure thereon received on each first conductive contact surface centered thereon by the cap centering portions and adapted to make electrical bridging contact between the first and second conductive contact when its curvature is inverted upon application of pressure thereon