Silicone Rubber Keypad 0311
The technology uses the compression molding properties of silicone rubber to create angled webbing around a switch center. On depression of the switch the webbing uniformly deforms to produce a tactile response. When pressure is removed from the switch the webbing returns to its neutral position with positive feedback. In order to make an electronic switch a carbon or gold pill is placed on the base of the switch center which contacts onto a printed circuit board when the web has been deformed. It is possible to vary the tactile response and travel of a key by changing the webbing design and / or the shore hardness of the silicone base material. Unusual key shapes can easily be accommodated as can key travel up to 3mm. Tactile forces can be as high as 500g depending on key size and shape.
The snap ratio of a keypad determines the tactile feel experienced by the user. The recommended snap ratio for designers to maintain is 40% - 60%; if dropped below 40% the keys will lose tactile feel but have an increased life. Loss of tactile feel means the user will not receive a "click" feedback during actuation.