Shielding Options for Membrane Switches
Electrical shielding can be incorporated into a membrane switch to help address electrostatic discharge and electromagnetic interference. The right approach depends on the product’s electronics, operating environment, and performance requirements.
CSI Keyboards works with customers to integrate shielding into custom membrane switch and keypad assemblies.
Why Add Shielding to a Membrane Switch?
Some applications require additional protection from electrical interference or electrostatic discharge. A shielding layer can be incorporated into the switch assembly and connected according to the product’s electrical design.
The material, coverage, and connection method all affect how the finished assembly performs. Shielding should be evaluated as part of the complete product design.
Understanding ESD, EMI, and RFI
ESD — Electrostatic discharge:
A sudden transfer of static electricity, such as a discharge from a user touching an interface.
EMI — Electromagnetic interference:
Electrical or electromagnetic energy that can disrupt the operation of electronic equipment.
RFI — Radio-frequency interference:
Electromagnetic interference occurring in the radio-frequency range.
Membrane Switch Shielding Options
Foil Shielding
A conductive foil layer, such as aluminum laminated to polyester, can be integrated into the switch construction. The layer’s coverage and termination are selected to suit the design.
Transparent Conductive Film
A transparent conductive film can be used when shielding is needed over an area that must remain visible, such as a display window.
Printed Conductive Shield
Conductive ink can be printed as a grid or another pattern within the assembly. The pattern is selected based on the coverage, optical, and electrical requirements of the product.
EMI Mesh
A conductive mesh can be cut to the keypad’s shape and incorporated into the internal layers of the assembly.
Shield Connection Options
The shielding layer also needs an appropriate connection for the product’s electrical design. Options may include:
- Tab: Connects the shield to a suitable point on a back panel or enclosure.
- Connector: Routes the shield through one or more contacts in the circuit tail connector.
- Wrap-around: Extends the shield around the switch to make contact with the chassis.
The appropriate termination and grounding approach depends on the complete assembly and its requirements.
Choosing the Right Shielding
Consider the product’s electronics, the type of interference or discharge being addressed, display windows, available space, and required test performance. CSI Keyboards can work with your team to select and integrate a shielding approach for your application.