Most rubber keypads are produced using silicone rubber and a process called compression moulding. Keypads are often the most important component in an electronic assembly as they form the interface between the user and the product. There are two main reasons we use silicone rubber to produce keypads, and these are aesthetic design and material properties.
Aesthetics, and what is possible?
Silicone rubber is easily coloured and can be matched to Pantone and Ral references at low cost. This is really important for keypads as they are not only used as the interface but are often used to help add value to the final product.
Silicone rubber can also be pad printed or toy store screen printed using special silicone based inks. These inks when applied correctly form a long lasting bond to the keypad and further enhance the design.
More advanced interfaces require backlighting; this can also be achieved with silicone keypads. To produce a backlit keypad the silicone rubber that is used is a high translucent silicone. The keypad is then sprayed with coloured silicone ink before having the legends laser-etched away back to the base silicone. This process produces a coloured keypad with clear graphics that can be backlit using LEDs.
Finally, silicone keypads with printing or sprayed colours have protective coatings applied; there are several coatings that can be applied to silicone rubber. You can add a silicone based hard spray coating that offers a silky soft touch to the keypad, PU spray coatings that add a much harder, smooth finish and also resin coating that are very high-quality, hardwearing coatings. All of these coatings protect the printing and add further value to the keypads.
Rubber keypads need to offer added value to the product. With all of the finishing options available, silicone certainly offers this. As well as aesthetics, however, the keypad needs to offer reliable operation and a long operating life – to ensure this; we use silicone rubber as the material.
Keypads are the main form of interface used in electronic assemblies; these assemblies are often used in extreme environments where temperature and water-resistance are important. Silicone has an excellent temperature resistance of -50 to +200 degrees C and can be exposed to wind, rain, and UV for long periods with almost no change in its physical properties. This makes it perfect material for keypads that are used in these types of assemblies.