Silicone rubber vs. plastic keypads

Molding process

Silicone rubber molding. Silicone is mixed with curing agents and other additives and then injected into a steel or silicone mold using a molding machine, where it is subjected to heat and pressure to cure and take the shape of the mold. The design of the silicone keypad, alignment of keys, and tactile features are dictated by the mold's cavities and the placement of tactile elements.

Plastic injection molding. After designing the keypad and selecting the appropriate resin, plastic keypads are created through a process called injection molding.

Tactile feedback

Tactile feedback is an important consideration for user experience. It is a response that tells the user the keypress was registered. The tactile force required for keypress and the actuation point can be customized to meet specific requirements in both silicone and plastic keypads.

Silicone keypads use silicone rubber webbing; when pressed, the silicone webbing around the keys will collapse and press a conductive pill on the keypad's circuitry, completing the circuit. The webbing provides the tactile feedback users feel when pressing a key.

On the other hand, plastic keypads provide tactile feedback through the use of a dome switch mechanism. A tactile dome is a small, flexible piece of plastic with a protrusion in the center. When a key is pressed, the dome compresses, creating a tactile feel and an audible click.

Ruggedness

Silicone is an excellent option for keypads because it is rugged, weather resistant, and can withstand harsh environmental conditions such as extreme temperatures, chemicals, and UV radiation. Because of this, manufacturers choose to use them in applications exposed to moisture, dust, and chemicals.

They are commonly used in industries requiring a ruggedized and reliable keypad, such as automotive and industrial equipment. The material is also non-conductive, which can be an advantage in applications where electrical conductivity could lead to interference or safety concerns.

The durability of plastic keypads depends on the specific plastic material used. While hard plastics like polycarbonate and ABS offer good impact resistance, they may not be as resistant to extreme temperatures and chemicals as silicone rubber. Plastic keypads are more likely to show wear and tear over time, especially in environments with harsh conditions.

Versatility

Silicone rubber is highly flexible which means it can be molded into a variety of complex and intricate shapes and designs. This is a significant advantage when ergonomic and customized key layouts are required. This flexibility also allows for a quieter keypress, making silicone rubber keypads more well suited than plastic for applications where noise reduction is critical, such as medical devices or industrial equipment. Plastic keypads have a wide variety of color options, but they offer limited design flexibility when compared to silicone rubber keypads.

Cost

Quality of materials and a complex molding process can make silicone rubber keypads costly, but their durability and long shelf-life result in cost savings over time since they are less likely to need maintenance or to be replaced.

Plastic keypads are generally more cost-effective to manufacture compared to silicone. Plastics are more readily available and molding techniques lead to lower production costs. However, it’s important to factor in replacement and maintenance costs when choosing plastic keypads, since they are less durable, particularly in extreme environments.