How Silicone Rubber Keypads Work
Long gone are the days of being restricted to traditional plastic keypads. Manufacturers are now using silicone rubber keypads, opening the doors to a whole new world of possibilities in terms of features and applications.
As you may already know, silicone rubber has special "compression molding" properties, meaning that it contours to the shape of the object(s) which it surrounds. This makes it particularly useful in the manufacturing of keypads, as it creates a webbing around the switch center. When the switch is depressed (e.g. a button is pressed), the webbing deforms to produce a light but noticeable tactile feedback response. The response may not be quite as strong as a motorized/mechanical vibration, but it's just enough to let the operator know that his or her command was properly registered; thus, increasing user satisfaction and accuracy. Consequently, when pressure is removed from the switch, the webbing returns to its normal shape and position while delivering positive feedback.
When choosing a silicone rubber keypad, pay close attention to its snap ratio. Basically, this is used to measure the amount of tactile feedback felt by the user. According to Wikipedia, the recommended snap ratio for most silicone rubber keypads is between 40 and 60%. Snap ratios lower than 40% will suffer from a loss of tactile feedback. On the plus side, however, they will greater strength and durability, prolonging their life expectancy.
Keep in mind that the tactile response of a silicone rubber keypad can be adjusted by altering the shape and position of the webbing design, as well as the shore hardness of the silicone material used in its construction. Depending on the key's size and shape, tactile feedback can measure as high as 500g.
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.
