Abstract: The inventive electroconductive adhesive comprises a resinous matrix, as a dispersing medium of conductive particles, of a polyester-based urethane resin admixed with a masked isocyanate compound as the curing agent. By virtue of the masking of the isocyanate reactivity of the curing agent, the adhesive composition is stable during prolonged storage under a hot temperature or high-humidity condition but can exhibit curing activity when the adhesive is heated at a temperature at which the isocyanate reactivity can be restored.

Abstract: The invention provides a novel key-board switching unit used, for example, in pocketable electronic calculators for producing binary-coded signals corresponding to contacting of movable contact points on the bottom surface of a keyboard covering pad and fixed contact points on the printed circuit board on which the covering pad is mounted when pushed with a finger tip or a pushing means. The printed circuit board in the inventive switching unit has a so fine and complicated circuit pattern that, in the prior art, one or more of jumping circuits crossing over a printed base pattern are indispensable resulting in much increased production costs while, in the inventive switching unit, the circuit pattern on the circuit board per se may be incomplete by the lack of such jumping circuits and, instead, the covering pad is provided with conductive connections corresponding to the lacking jumping circuits on the circuit board to form necessary jumping circuits when the covering pad is mounted on the circuit board.

Abstract: An electronic circuit board has protrusions of rubber-like material on the surface opposite to the surface on which the printed circuit is provided with terminal contact points located at positions in correspondence with the individual terminal contact points or with the individual groups of the terminal contact points, each of the groups being composed of the terminal contact points aligned in a row.