Mounting a laminated Touch Sensor on a Display

Integration

Mounting a glass with laminated Touch Sensor on a Display

Clean the LCD and the glass on which the Touch Sensor has been laminated. Use a soft, damp lint-free cloth with 10% dishwasher detergent to 90% water solution to clean the glass. The same solution can be used to clean the Touch Sensor, which should be cleaned with care to avoid damaging the sensor electrodes, the flat flexible cable, and its solder joints.

To mount the glass on an LCD, a suitable double-sided bonding tape (such as 3M VHB tape) should be applied on the bezel, around the perimeter of the LCD.

This mounting procedure creates an Air Gap between the LCD and the Touch Sensor. This air gap is necessary to reduce electromagnetic interference from the LCD panel. Interference levels differ depending on the LCD panel characteristics. The air gap may be between 1 and 10 mm, and should be as narrow as possible once there is no noise (EMI) visible in the touch signal. We recommend using an air gap of at least 2 mm. In all cases, this should be checked before the final integration (i.e. test different airgaps by introducing a temporary object, like a non-adhesive foam or cork spacers along the LCD bezel, to adjust the distance between the LCD and the touch sensor laminated on glass, and test the touch performance).

The double/sided bonding tape should be non-sulfurous and must maintain its adhesion properties at any temperature the LCD may reach during normal use.

Fig.1

Having applied the double-sided bonding tape, place the laminated Touch Sensor onto the LCD panel with the Touch Sensor facing the LCD (Fig.2 and 3)

Fig.2

Fig.3

When positioning the laminated Touch Sensor over the LCD, carefully align the viewing area of the LCD with the active area of the Touch Sensor laminated on the glass. It is also important to take into consideration the position of the tail (flexible flat cable) when planning the integration to determine the best position for mounting the PCB controller on the back of the LCD.

In this respect, take into account that the backlight of the LCD is usually the noisiest component (EMI). Traditionally, the controller is placed on one of the sides of the display. If your Touch Sensor is a "side tail" version, the side of the sensor where the PCB Controller attaches to should be on the same side of the LCD backlight since the signal is stronger here, thus minimizing the impact of the noise from the backlight. Contact your LCD manufacturer for more information regarding the backlight position.

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