Keypads silicone

In consumer markets, keypads, baby bottle nipples, and pacifiers are said to be the applications for molded silicone products with greatest growth potential. Silicone elastomers are particularly well suited for food contact and medical applications. 

These are typically built on a polyester base membrane (PETP, 35 pm, copper-laminated) with a polyester spacer membrane, safety chamber and front membrane. The snap disc being gold plated stainless steel. Other designs use electrical contacts made from silver, silver on carbon or carbon only. Keypads may also be made from conductive silicone rubber. Conventional computer keyboards made from ABS, polyester or other polymers, may be covered by a polymer overlay to protect it against dirt, dust, water or other substance present in a hostile environment. Polyester and PVC overlays are used in a wide variety of applications with computer and instrumentation equipment in dental and medical healthcare and other areas. Typical casing materials include PC and polychloroprene. 

The combination of two soft components such as silicone rubbers of different hardness, colour, electrical conductivity, etc., is also commonly used in a wide range of applications. Typical applications are electronic keypads (as for calculators, control panels, etc.), where electrically conductive silicone rubber (so-called conductive pills required for establishing an electrical contact when a key is pressed), is overmoulded with an insulating silicone rubber pad, and cable accessories, containing an insulator body with a conductive silicone core (so-called stress cone) which allows better control of the shape of the electric field. 

As an example consider silicone keypads. The first silicone components are conductive pills. They can be incorporated using inserted part technology as well as in two-component injection moulding, the latter preferably using LR. 

Fig. 3.12. Microcomputer keypad made from a single moulding of a liquid silicone rubber, with its underlying membrane switching circuit. (Sinclair Research, Haffenden and NFI Electronics.)...

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