S-TouchTM Capacitive Touch Controller PCB Layout Guide 1

Introduction

This application guide provides design layout guidelines for the structure and layout of various PCBs (printed circuit boards) (such as FR4, flexible PCBs, or ITO panels) used in S-TouchTM capacitive touch sensing design.

Among the PCB substrates available in the current market, FR4 is the most commonly used. FR4 is a glass fiber-reinforced epoxy resin laminate, and PCBs can be single-layer or multi-layer.  diode

When the dimensions of the touch module are constrained, using a single-layer PCB is not always feasible, and four-layer or two-layer PCBs are typically employed. We will use the most common two-layer PCB as an example to introduce the PCB layout guidelines.

PCB Design and Layout

In a two-layer PCB, the S-TouchTM touch controller and other components are arranged on the bottom layer, while the sensor electrodes are placed on the top layer.

Figure 1 Structure of the Capacitive Touch Module Based on a Two-Layer Board

The tuning matching capacitors required for each sensor channel can be directly laid out beneath the corresponding sensor electrode. It should be noted that the S-TouchTM touch controller, also laid out in the lower layer, must ensure that no sensor electrodes are present on the corresponding upper layer. The blank areas of the upper and lower layers can be filled with meshed grounding copper foil.

Figure 2.1 Top Layer of a Two-Layer PCB Board

Figure 2.2 The bottom layer of a two-layer PCB board  diode

Design rules

Layer 1 (Top Layer)

The sensor electrode is located on the top layer of the PCB (the upper end of the PCB is fixed to the cover plate). To improve sensitivity, it is recommended to use a sensing electrode with dimensions of 10 x 10 millimeters. A smaller sensing electrode can be used, but this will reduce sensitivity. Additionally, the size of the sensing electrode should not exceed 15 x 15 millimeters. If the sensing electrode exceeds this size, it will not only reduce sensitivity but also increase susceptibility to noise.  diode