Covering areas such as the artwork design, embossing, force/travel considerations and key elements that need to be included when preparing CAD drawings, our Membrane Keypad Design guide gives designers an overview of all the elements that must be considered when specifying a membrane keyboard design.
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In many applications it is desirable to emboss the keys of a switch. The phrase “Pillow Embossing” is used to describe keys that are raised and flat on the top. This is most commonly used with metal domes. “Rim Embossing” is used to describe only the border of a key being raised and is frequently used in non-tactile applications but not limited to . “Dome Embossing” is when the button is formed into a raised circular dome shape.
Steel rule dies are normally used to fabricate the various layers of a membrane switch. Standard tolerances should be +/- 0.381 mm (.015”). Tolerances of +/- .254 mm (.010”) can be held on critical dimensions such as the perimeter or cut-outs.
Hole centre to hole centre tolerances of +/- .127 mm (.005”) can be held. Tolerances on very large parts will be greater.
The switch layers under the overlay will typically be fabricated smaller than the overlay. This allows for die cutting and assembly tolerances. All layers will typically be inset from the overlay at all edges and cut-outs by .015 inch