AN3431

Mechanical construction considerations

Doc ID 019017 Rev 1

7/18

2

Mechanical construction considerations

2.1

Stack up

The mechanical stack up is shown in Figure 3. The conductive top cover is normally metal.

An insulating layer may be added without modifying the behaviour of the PresSense buttons.

The middle layer is a spacer with cut-outs to allow for the deflection of the top cover at

predetermined positions. The bottom layer is the PCB with the sensor pads as copper

pours. An additional mechanical bracket/support layer can be added.

Figure 3.

Mechanical stack up

The parameters that impact touch and detection are:

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The insulation layer material and thickness

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The top cover material and thickness

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The thickness and the hole size of the spacer

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The size of the sensor pad and the routing of the touch sensing signals

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The mechanical construction and the rigidity of the overall touch module.