Thin film switches, often referred to as membrane switches, are momentary switches with a user interface to control equipment and machines. Here are the typical technical parameters to consider when working with or designing thin film switches:
Electrical Parameters:
- Contact Rating: Refers to the maximum current and voltage the switch can handle.
- Contact Bounce: The amount of time before the switch settles into a stable state after being actuated.
- Contact Resistance: The resistance between the contacts when the switch is closed, typically in the range of a few ohms.
- Insulation Resistance: The electrical resistance between the conductive parts of the switch and the grounding points, measured when the switch is open, typically in megaohms (MΩ).
- Dielectric Strength: The maximum electric potential the switch can withstand without breakdown.
- Circuit Rating: Normally specifies the voltage and current the switch can carry. For example, 5V DC at 100mA.
Mechanical Parameters:
- Actuation Force: The force required to close the contacts of the switch, generally measured in grams or newtons.
- Life Cycle: Specifies the number of actuations the switch is rated for before failure and is typically tens of thousands to millions of cycles.
- Actuation Travel: The distance the switch surface moves when pressed, usually measured in millimeters (mm) or inches (in).
Environmental Parameters:
- Operating Temperature Range: The range of temperatures in which the switch can operate without failure or degradation.
- Storage Temperature Range: The temperature range suitable for storing the switch without causing damage.
- Humidity: Level of resistance to moisture, often expressed as a percentage over a given temperature range.
Physical Parameters:
- Thickness: The overall thickness of the switch layers, typically a few millimeters.
- Size: Dimensions of the switch, which can vary greatly depending on the application.
- Number of Keys: The number of individual keys or switches within the membrane switch panel.
- Overlay Material: The type of material used for the graphic overlay, commonly polyester or polycarbonate.
- Substrate: The material used as the base of the switch, such as PET, PC, or PVC.
- Adhesive: Type and thickness of the adhesive layer used to mount the switch onto a surface, which must be compatible with the surface energy of the substrate.
Graphic and Interface Parameters:
- Graphics: The color, design, and layout specifications for switch labels, logos, and other interface elements.
- Embossing: Some switches have raised areas to provide tactile feedback.
- Windows and LEDs: Location and size of clear areas for displays or light indication.
- Tail Length and Connector: Length of the conductive tail and type of connector used, like ZIF connectors, pin headers, or solder tabs.
Certifications and Compliance:
- IP Rating: Ingress protection rating, which defines the level of sealing effectiveness of electrical enclosures against intrusion from foreign bodies and moisture.
- RoHS: Restriction of Hazardous Substances, which restricts the use of certain hazardous materials found in electrical and electronic products.
- REACH Compliance: Ensures that chemicals within the product, above a certain threshold, are registered and evaluated in terms of their environmental impact.
- UL Listings: Safety certification for component safety given by Underwriters Laboratories.
When designing or specifying a thin film switch, it's important to consider all these parameters to ensure compatibility with the intended application. Additionally, the manufacturer’s datasheets and specifications should be referred to for precise design and application guidelines.