S-TouchTM Capacitive Touch Controller PCB Layout Guide 3

In the previous introduction of the two-layer FR4 PCB, grounding copper foil was used to fill the blank cross-sectional area of the PCB. Grounding copper foil can help shield the touch module from external noise sources and stabilize the inherent capacitance of the sensor circuit. diode

However, when using grounded copper foil, several issues need to be noted in advance. This is because grounding copper foil increases the inherent capacitance of the sensor and also increases the possibility of false detection caused by water droplets.

Design Guidelines for Grounding Copper Foil:

It is recommended to use mesh grounding copper foil instead of solid grounding copper foil. It is recommended to use 20% mesh grounding copper foil (trace width of 6 mil, mesh size of 30 mil). The angle of the grounding copper foil should be set at 45 degrees.

The distance between the sensor and the grounding copper foil should be at least 0.5 millimeters, and it is recommended to use 0.75 millimeters.

The gap between the sensor signal trace and the grounding copper foil should be at least twice the width of the trace.

For a four layer PCB, if the sensor signal traces placed on the third layer are larger than 10 centimeters, it is recommended not to place a grounding copper foil on the bottom layer in order to minimize the capacitance load of the long traces.

If partially conductive materials are used for the laminated board, it is recommended not to install grounding copper foil on the top layer.

If the capacitive induction system needs to work in a humid environment, it is recommended not to install grounding copper foil on the top layer.  diode

Basic Function Description and Guidelines for Sensors

Capacitive sensor electrode refers to a conductive electrode plate used to measure finger capacitance. It is connected to the input of the sensing channel of the S-TouchTM controller. Sensor electrodes can be made in various geometric shapes and sizes to have different functions and applications.

touch button

The basic function of touch buttons is to detect whether a finger is touching them. The S-TouchTM controller can measure the capacitance of touch button sensing electrodes. If the finger is close to the touch button, the occurrence of finger touch will be detected when the measured capacitance change exceeds the pre-set threshold.  diode