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Engineering of a silicone rubber keypad
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There are two main types of coatings, each with distinct advantages.
- PU coating - offers great abrasion resistance and durability, a smooth finish ranging from matte to high gloss.
- Silicone coating - with non-stick properties and excellent moisture and temperature resistance.
The choice of surface treatment of silicone rubber depends greatly on your specific requirements in terms of mechanical properties, environmental resistance, and the desired finish.
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When it comes to shapes and 3D design, silicone rubber keypads have a unique advantage compared to other keypad types.
The silicone overlay is made using compression-moulding technique. This provides a great options for sculpting the material to different shapes.
Concave buttons, distinct recesses around keys, split lines between different areas, multi-level design are some of the sculpting opportunities that silicone rubber offers.
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In general, we distinguish between three main options for adding colour to your silicone rubber keypad.
- Co-moulding involves molding of two or more different coloured silicone rubbers together. This colouring method ensures high durability of the colour.
- With spray-painting, you can add fine graphic details to selected parts of the keypad.
- Silkscreen printing is also an option - although with certain limitations as it requires flat surface for application of the ink.
The robustness of silicone rubber opens up for the possibility to laser-engraving or laser-etching. which in principle means that the colour applied as the top layer is removed at certain places to reveal a different colour or the original translucent colour beneath. -
Lighting in silicone rubber keypads enhances both aesthetics and functionality.
- Status indicators provide immediate, clear feedback through backlit windows or symbols, signaling device status or actions needed.
- Deadfront or ghost effect lighting has a more sleek modern look. The symbols remain "hidden" and more discreet than status indicators.
- Backlighting serves a functional purpose, ensuring keys are visible in dark conditions, facilitating ease of use anytime.
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The tactile click in silicone rubber keys is achieved using:
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metal domes as the most common method for creating the click of a keypad, with wide range of shapes and sizes of the domes to choose from.
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tactile switches, often used with a PCB as the circuit layer in the keypad, ideal for designs where space is tight.
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silicone click:, created by designing the silicone keys to snap when pressed, equipped with a carbon pill for connectivity with the circuit. It’s a sustainable solution that reduces the number of layers needed.
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In the construction of a silicone rubber keypad, the circuitry is typically crafted from one of the following materials, each offering distinct advantages:
- PET - known for being both economical and widely used, PET stands as the most accessible option.
- FPC - this option utilizes a copper-based foil known for its excellent conductivity and flexibility, making it ideal for applications requiring bending.
- PCB - ideal for situations requiring rigidity and the ability to solder components directly to the PCB.
Selecting the ideal circuit layer material for your keypad is determined by the product's intended use environment, along with its electrical and mechanical design requirements.
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Finalizing the mechanical and electrical integration of a keypad is crucial for the overall design of your keypad solution. As you navigate through the design process, it’s important to consider several key aspects.
For mechanical integration, reflect on:
- What method will you select for securing the silicone keypad to your device? Options include adhesives, screws, or press-fit techniques.
- Consider the installation orientation of the keypad. Will it be mounted to the front, back, or side of the device?
Business Development Manager, Mekoprint
Domenic Breitbart Nielsen