Silicone Keypad Technology
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 PCB when the web has been deformed.
Customization of Silicone Rubber keypads
Silicone is an extremely popular material due to its low cost and exceptional Engineering properties, which provide an extremely wide temperature range, Long life, and robust flexible sealing capabilities, along with its attractive tactility and the possibility to add shape, Colour and form to any design.
Hardness - Silicone keypads can be supplied in a wide range of hardness from 40A Shore to 90A Shore Hard (or a mix of different hardness in the same keypad). This enables the designer to utilise a softer shore hard base such as 40A or 50A Shore which can allow the added benefit of crush ribs designed to provide a water tight sealing (IP67) yet still have a harder key top such as 70A or 80A Shore hard.
Travel - Keypads can also be designed with a wide range of travel and actuation force typically 0.6mm to 2mm and 50g to 350g. Allowing the Designer to tailor the switch response to their application, However if you have any requirements outside thses please contact us and we will be happy to provide expert advice for your chosen application.
Colour - Keypads can also be moulded in any colour by either referencing popular colour charts such as Pantone and RAL to name but a few or alternatively Colour matching to sample is also available.
Colour can be blended into the Silicone to provide an opaque base or alternatively translucent Silicone can be used which will allow for Keys or Light Guides to be illuminated from behind, you can also have a mix of both in the same keypad.
Various colours can also be added by Screen printing, Spray Painting with Laser Etching to allow for backlighting, which can then have a clear Silicone or Polyurethane lacquer coating for wear resistance and environmental protection.
Hard Key Tops - In Addition Hard Plastic Key Tops can be adhered. These are injection moulded which can be in any colour or clear plastic with Screen Printing, Spray Painting or Electroplating and Laser Etched to allow backlighting all of which, are finished with a hard wearing lacquer.
Resin Key Top - An Epoxy Resin can be applied to the key surface to provide a hard top with the benefits of protecting the ink below, creating a hard top without the expense of injection moulded keycaps and also the aesthetic appeal of a gloss finish to add contrast within a design.
Additives - Long Life Silicone and UL Flame Retardant additives and Luminescent grades are also available for certain applications.
Keypads can incorporate Carbon Pills (inserted in mould), Gold Pills, Carbon Ink (printed to actuator surface), Metal Click Dome (Custom Disc Arrays also available from Diamond HMI) or Polydome Mylar with a Carbon or Silver contact Pad.
All of the above can be either incorporated in the keypad assembly or supplied separately and we can even supply the complete solution either attached to a Flexible Printed Circuit (FPC) or FR4 PCB. In order to maximise the electrical life cycle of your product it is vital that the correct switching solution is used. Diamond HMI will advise customers on the best solution for their application.
Tactile Response Of A Key
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.
Diamond HMI Silicone Rubber Keypad Design Guide
Many of the parameters above are highlighted in greater detail in our Rubber Keypad Design Guide which can be downloaded at the bottom of this page or experienced first hand by ordering our Rubber Keypad Design Tool.