Shielding - Design Considerations
Overview | Connection | Design Considerations | Types
OVERVIEW
In order for GGI International to achieve an efficient integration of the chosen shielding method, certain basic design criteria must be respected. GGI's engineering team is available to assist you with your shield selection.
- Copper mesh:
- Allow for an additional thickness of at least 0.015" in order to integrate this type of shielding in your keypad assembly.
- Aluminium foil or polyester sheet screenprinted with a grid pattern of graphite and silver ink:
- This type of shielding will not protect LCD or LED windows
- When designing the electronic connection of the keypad connector, always assign grounding to the exterior traces
- Example 1: for a membrane keypad having 15 traces, assign either trace 1 or 15 for grounding.
- Example 2: for a keypad requiring 2 traces for grounding and having a total of 15 traces, assign the grounding function to either traces 1 and 2, traces 14 and 15 or traces 1 and 15.
Polyester graphic overlay:
- Even if the polyester graphic overlay can absorb up to 2 Kv per thousandth of an inch in thickness of raw material, the electrostatic discharge (ESD) seeks a breach in the graphic overlay and will circumvent it to infiltrate the edge of the keypad. For this reason, an effective ESD shielding is carried out by adding additional shielding under the graphic layer.
- Shielded window using ITO pulverization:
- A pre-determined space without the presence of components must be reserved all around the window in order to allow the internal connection for the shielding.
- It is recommended to leave a space of at least 0.200" between the edge of the window and a cutout.