Shielding - Connection
Overview | Connection | Design Considerations | Types
OVERVIEW
In order to ensure protection of the membrane keypad, the shielding layer must be grounded by redirecting the discharges or interference towards a neutral point. GGI International is able to offer you a wide range of grounding options. Our team of qualified engineers will guide you towards the best solution for your application.
TYPE OF CONNECTIONS: GGI International offers four basic types of connection options:
Direct mechanical connection: The design of the shield layer incorporated in the membrane keypad includes a tail or tab extending beyond the surface area of the keypad. This tail or tab is punctured in order to receive a screw or a rivet which can be affixed to a metal case or a ground wire.
- Advantages:
- Simple, direct and always 100% effective
- Does not depend on an electronic function to operate
- Solid and resistant to vibration and shock
- Disadvantage:
- Requires connection point in the enclosure to install the shielding
- Advantages:
Electronic connection: The design of the membrane keypad shielding includes a tail placed directly above the tail of the circuit. The shielding tail includes one or more traces which will be connected through the connector. The other traces are set aside in order to avoid interference with the circuit. The positions corresponding to the shielding traces will be assigned with a grounding function directly on the electronic module on which the keypad will be installed.
- Advantages:
- The connection is made within the connector
- Solid mechanical contact within the connector
- Does not require any external mechanical attachment during the final keypad assembly
- Disadvantage:
- The grounding function must be integrated in the electronic module on which the keypad will be installed
- Advantages:
Mechanical connection using conductive adhesive:
The design of the membrane keypad shielding includes a tail or a tab extending beyond the surface area of the keypad. A pre-cut piece of conductive adhesive is applied on the tail or tab and the latter is affixed to a metal case or housing- Advantages:
- Simple and direct
- Does not depend on an electronic function to operate
- Disadvantages:
- Requires a conductive surface in the enclosure to bond to.
- Adhesive bond must not be tampered with as it will weaken.
- Advantages:
Connection with ferrite: Exclusively used in specific applications requiring an increased RFI protection. The ferrite is installed on the circuit tail of the membrane keypad.
- Advantages:
- Ease of installation
- Highly effective for this type of protection
- Disadvantages:
- Requires the presence of a longer circuit tail
- Space inside the assembly must be sufficient to accommodate the tail and ferrite
- Advantages:
- Connection using ITO mainly on windows: The connection is achieved on the inside of the keypad assembly. The ITO film is applied to the rear window of the graphic overlay using optically clear adhesive. A selective piece of conductive adhesive is applied to the rear of the ITO film, which will come into contact with the balance of the shielding during keypad assembly.
- Advantages:
- Internal connection with the membrane keypad.
- Provides a continuous shield of the membrane switches and display window.
- Disadvantages:
- ITO films can hinder the optical quality of a window
- Applying ITO film to windows with large surfaces can increase the risk of optical impurities
- Requires the application of a secondary shielding for the balance of the keypad
- Requires additional space around the window in order to achieve an effective contact between the layers
- Advantages: