Membrane Keypads - also sometimes known as Membrane Keyboards, offer a high level of customisation to meet designer`s ergonomic and aesthetic criteria as well as satisfying more obvious parameters such as robustness, Electrical Efficiency, Chemical Resistance, Ingress Protection, Operational life and cost. A membrane assembly is constructed from Polyester films on which graphic and conductive inks are printed and electrical contact is made by pressing the finger onto the contact area and broken when the finger is released. With low cost tooling allowing customers to get to market with little expenditure a membrane switch can be either touch sensitive or have a customised tack-tile feedback providing a momentary switching of low voltage, low current with typical ratings of 50uA – 10mA, <100V and a standard maximum switch rating of 500mW. However these can be increased with the use of PCB or FPC Polyamide base layers.
Graphic Overlay – Generally produced from Polyester due to its high flex nature and excellent scratch and chemical resistance the material is available in various thicknesses with either Gloss, Fine or Velvet Texture, UV Resistant or Anti-Microbial Coatings.
Printing On-Surface - The surface can either have a clear varnish printed onto it (to provide a clear window in textured material) or Gloss base material with a printed texture to allow selective areas to be textured and other parts such as windows, Button areas, logos to be Gloss.
Printing Under-Surface Colour – The overlay can be Screen printed or digitally printed Under-surface, which provides a high level of protection to the ink inhibiting the effects of any wear. Typically the colour is applied using screen printing providing an Opaque or Tinted colour finish (Tint for LED and Display windows). There are also Chrome Inks, Metallic Inks, Luminescent Inks available, which can have Vignette patterns or where finer detail is required digital printed can also be used. Colour can be chosen by referencing either popular colour charts such as Pantone, RAL to name but a few or alternatively Colour matching to sample is also achievable.
Embossing – Various embossing styles such as Polydome, Raised Pillow, Rim or de-embossing can be achieved to add a third dimension to the design. Embossing can also be applied to the circuit below the graphic layer to provide a tactile switch response.
Windows – These tend to be either clear or Tinted for Displays but can also be positioned in locations to allow inter-changeable printed inserts to be fitted between the graphic layer and the circuit. This provides further flexibility in the design to allow customers to use them for changeable printed inserts.
Circuit – Generally constructed from laminated Polyester and adhesive layers the conductive tracks use a silver based Ink however where applications require smaller connection areas, Polyamide FPC with photo etched and gold plated tracks can also be used. These provide a tail pitch down to 0.5mm or less, the circuit can also be supplied utilising a PCB base within the construction all of which can have SMT components fitted. The circuit can either be flat non-tactile, Embossed in various sizes to provide a custom travel and force or incorporate metal click domes all of which, are available in a wide range of shapes and sizes. They may also incorporate electronic embedded components the most popular being LEDs. The benefits of Membrane circuits are that they provide a low cost switch solution allowing the designer to utilise their controller for more complex functions and maximise efficiency through size reduction. The circuits are also sealed and the switches have no solder joints as a conventional switch may have so enhance the customer product quality because joints can be seen as a source of failure within a design.
RFI / EMC / ESD – Shields can be printed between the graphic and on top of circuit layers and earthed by either tab`s in the top layer or through the circuit tail. In addition ITO layers can be incorporated within the assembly to provide the same protection to the window area. We also design the circuits to withstand high levels of ESD exposure.
Illumination – Membrane Keypads can be backlight by incorporating an Electroluminescent or Optical Fibre layer or simply more popularly incorporating LED`s within the design.
We also supply membrane circuits with Silicone Rubber Overlays to add a more dynamic 3D effect please take a look at our CombiKey keypad page for further information.