Spacerless keyboard switch circuit assembly

A switch circuit assembly comprising:

• a unitary base member having a front surface and having a fold line for dividing the base member into a first section and a second section;
• a plurality of first conductor traces on the front surface of the base member extending along preselected paths on the first section;
• a plurality of second conductor traces on the front surface of the base member extending along preselected paths on the first section, across the fold line and along the second section;
• at least one first switch contact on the front surface of the base member on the first section, each first switch contact electrically coupled to at least one of the first conductor traces;
• at least one second switch contact on the front surface of the base member on the second section, each second switch contact electrically coupled to at least one of the second traces, each first switch contact being located to face at least one of the second switch contacts when the base member is folded along the fold line;
• an insulative layer applied over selected regions of the base member to cover selected regions of at least one of the first and second conductor traces to insulate the first conductor traces from the second conductor traces when the base member is folded with the first and second sections in touching relationship to each other;
• each of the switch contacts on at least one of the first and second sections comprising;
• a conductor ply, and
• a pressure sensitive layer applied over the conductor ply, the pressure sensitive layer comprising a semiconducting material applied to be in intimate electrically conducting contact with the conductor ply, the pressure sensitive layer defining a first exposed surface with a multiplicity of microprotrusions of the semiconducting material extending therefrom for providing a multiplicity of surface contact locations, the other of the first and second contacts facing the first exposed surface defining at least one facing contact, the junction between the first exposed surface and its facing contact defining a surface junction, said surface junction being electrically non-conductive when the first exposed surface noncompressively touches the facing contact and being conductive when the first exposed surface compressively touches the facing contact.