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Projected Capacitive Touchscreen Integration

Proper integration is vital for the proper function of a touch system. The following will discuss the various methods of mounting an AMT PCI touch panel to a front bezel and to a LCD module.

Terms

Touch Screen Drawing

fig.1

There are two types of AMT PCI touch panel drawings: one shows both a ”Key Area” and an ”Active Area,” while the other shows only an ”Active Area.”

  1. Cover Glass: The touch side consists of a passive glass covering secured on top of the PCI sensor.
  2. Film Sensor: This is the size of the PCI sensor.
  3. Viewing Area: The dimension of the viewing area is the transparent area of the touch panel.
  4. Active Area: This is the touch panel function area.
  5. Key Area: Touch functionality in the Key Area is designed for high accuracy and sensitivity, thus allowing smooth touch operations at the perimeter.
  6. Tail: The tail is the touch panel circuit connection line.

LCD Display Module Drawing

fig.2

  1. Outside Dimension: The overall external size of the LCD module including the metal casing that houses the LCD screen and the PCB.
  2. Bezel Opening: Also known as Opening Area. This is the LCD metal frame opening. The metal frame must be fully covered by the system’s front bezel.
  3. Active Area:  This is the display area of the LCD module. The touch panel’s key area (or active area, if key area is not applicable) should match the LCD active area.

Design Notes

  1. AMT provides two different PCI structures:
    1. A standard Glass-Film-Film-Film (GFFF) touch panel structure and a Glass-Film-Film (GFF) for certain models.
    2. True flat PCI touch panel with décor cover glass.
  2. Integration
    The edge of the front bezel should be placed between the viewing area and active area of the touch panel. Bezels made of conductive materials must not touch the surface of the touch panel.
    Décor glass PCI does not require a front bezel. When installing Décor glass PCI, be sure to leave a sufficient gap between the LCD and the touch panel.
    fig.3
  3. Gap
    The PCI touch screen is sensitive and highly susceptible to electrical noise. Interference may result in false touch events. Thus, it is necessary to leave a gap between the touch panel, the LCD panel, and the bezel. See below.
    fig.4
  4. Front Gasket
    The front gasket acts as a buffer when the touch panel is mounted to the front bezel. Single-sided adhesive as a front gasket is recommended when bonding a LCD with the touch panel. The front bezel must not come in contact with the surface of the touch panel. The suggested thickness for the gasket is more than 0.5 mm (1.0 mm is recommended).
  5. Tail
    • The minimum bending radius of the FPC tail is 1.0mm. It is important to position the touch panel tail in such a way that its bending radius is greater than the tail’s specified bending radius.
    • If the route of tail comes into contact with sharp components, make sure both sides of the tail are protected with non-conductive materials (such as PORON® or gaskets) that are at least 1mm thick.
  6. Mounting Controllers
    • Ensure the surface, tail stiffener, and IC side of control board are facing up.
    •  Grasp the tail by the stiffener section and insert into the connector. Make sure the touch panel’s tail(s) is/are inserted all the way into the connector, and lock the connector properly. ZIF connectors should be fully locked.
    • Connect the other FCP connectors securely one by one.
    • Assembly completed.
  7. Others
    • For the best no-interference touch performance, 3 pin power plugs with ground for your PCI touch system are strongly recommended.
    • Do not touch the surface of the PCI sensor during system startup. This prevents the PCI touch system from picking up an in-accurate base signal.

Reiteration of Design Notes

  1. The touch panel’s viewing area should be placed between the LCD’s active area and bezel opening.
  2. The key area (or active area if key is not applicable) of the touch panel should match the LCD active area.
  3. The design of the front bezel must fully cover the touch panel’s silver bus lines.
  4. The touch panel should be insulated from the front bezel of the system with non-conductive materials if the front bezel is made of conductive materials.
  5. Make sure both sides of the tail are protected with non-conductive materials (such as PORON® or gaskets) that are at least 1mm thick.
  6. Please wear an antistatic wrist strap during the control board installation process.