The Anatomy of a Membrane Switch

Many of our customers come to us looking for an effective way for a user to interact with their product or equipment. One of the best ways to achieve this interaction is with a custom membrane switch designed by RSP.

Over our 50 years in business, we have worked with a variety of clients to design their perfect custom membrane switch. During all of those projects, we have learned that teaching has been one of our greatest assets to execute the perfect membrane switch for our clients.

Let’s start with a quick lesson on what a membrane switch is, anatomy of a typical membrane switch and a few common custom elements.

What is a Membrane Switch?

Membrane switches, also known as membrane panels or membrane keypads, are electrical switches with a user interface to control equipment and machines.

What kinds of industries are membrane switches used in?

Membrane switches can be created for a variety of industries and environments. Some common uses are in appliances, consumer products, industrial machinery, medical instruments and automotive industries.

Membrane Switch Assembly

Although membrane switches can be custom in many ways, a typical switch is designed with 4 – 6 layers to function properly. The layers include:

membrane-switch

  • Presentation Layer
    • Also known as a graphic interface, is the top layer of a membrane switch to create a visual interaction between the user and the machine.
    • You can learn more about our graphic interface capabilities here.
  • Adhesive Layers
    • Typically 5 layers where adhesive glue is used to bond the unit together.
  • Separation / Spacer Layer
    • This layer is commonly made of polyester.
    • In a non-tactile switch, this layer creates the space between the upper and lower circuit so that when the user presses down the upper and lower circuits close and make contact.
    • In a tactile switch, this layer has a metal dome which sits in the space. If there were no spacer layer for the dome it would be pre-actuated and not have a nice ‘snap’ feel.
  • Circuit Layer
    • The circuit is required to move electricity (electrons) from one place to another.  Therefore, this is layer which allows the transfer of commands to machine. To do this, there is a printed conductive silver ink on circuit typically made out of polyester.
    • In some cases, this layer may include surface mount devices such as LED and resistors.

Additional Custom Elements

Apart from the typical layers described above, there are plenty of additional custom elements which can be added per a customer’s product specifications. Those additional elements include:

  • Indicator LEDs:
    • The indicator is used to communicate an action or function which is currently in process or completed.
  • Backlighting:
    • There are various ways to incorporate backlighting within membrane switches:
      • LEDs
        • This type of backlighting is best for small icons or symbols.
      • LGF – Light Guided Film
        • LGF technology is designed to evenly distribute bright and uniformed light while reducing the amount of LEDs needed for proper lighting. Thus, this is one option to help save power consumption.
        • The success of this technology has made it one of the common methods of interface backlighting.
      • Electroluminescence – EL Technology
        • EL would be an additional thin layer between the graphic overlay and the circuit. EL uses a phosphor deposit to illuminate the switch.
        • A common use of this technology is cell phones and GPS systems.
  • Electrostatic Discharge Shielding – aka ESD Shielding
    • The design of a membrane switch sometimes requires ESD shielding where static discharge could damage the electronics the membrane switch plugs into.
    • The shielding layer does not eliminate static, it simply routes a conductive trace to a safe grounded contact to eliminate damage.
    • A common use of ESD Shielding is within medical instruments.

You can learn more about designing a custom membrane switch with RSP or call one of our sales representatives to for any questions you may have.