Physical properties of silicones
Silicones are the polymers that consist mostly of silicon (sometimes mistakenly spelled cilicone), oxygen, hydrogen and carbon. These polymers are used in production of silicone rubber, silicone resign, silicone grease and silicone oil. Silicones possess several extremely useful properties that give them clear advantage over the other materials used for the same purposes.
Silicone rubber keypads are:
- Chemically inert
• Thermally stable, meaning that their physical properties do not change over a large range of temperatures (-100°C to 250 °C)
• Resistant to microbiological growth
• Waterproof (this quality allows the use of silicones as watertight seals)
• Non-sticky, which comes in handy when silicon rubber buttons are used in the electronic products that require manual operations (oscilloscopes, ammeters, programmable logic controllers, etc)
• Electrical insulators
• Resistant to ultraviolet light (UV light), ozone and oxygen
Silicones as chemical compounds
Silicones rubber is a mixture of organic and inorganic components whose general chemical formula is [R2SiO], where R stands for either methyl or ethyl or phenyl organic groups of molecules, depending on the application. (Si-O-Si-O-Si-O …) are the chains of inorganic silicone-oxygen molecules.
Silicone rubber’s properties depend on spatial positions of the Si-O chains and the chain lengths. It is possible to change physical properties of a silicone rubber compound by changing positions of its molecules.
Advantages of using silicone rubber buttons in electronic products
Electronic products such as remote controls, industrial keypads, medical devices, calculators and many other small electronics have incorporated the use of silicone rubber buttons. Silicone rubber buttons are resilient to many external forces, provide tactile feedback, and can be printed on and numerous other features. One of the most common features of silicone rubber keypads is molding a carbon contact pill on the backside. The carbon contact pill will complete a circuit on a PCB when the silicone rubber is pressed. This method of completing a circuit is cost effective and very reliable because it removes the need for a mechanical tactile switch.
When electronic devices are operated at low temperature, the buttons must still function properly when pressed. These buttons are often made out of silicone rubber because of its ability to withstand very low temperatures.
Ultraviolet light is used in many medical devices. Silicone rubber buttons are an ideal choice of relays for these devices because of silicone’s ability to resist the UV light.
Being non-toxic, silicone rubber buttons do not release harmful toxins into the atmosphere. Electronic toys for children are equipped with such buttons so that the children are not exposed to harmful toxins.
One of the main advantages of silicone rubber buttons is their low price. It makes sense for the companies producing electronic equipment to use these buttons to help keep their production prices low.