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I am designing circular capacitive touch pads of Dia:20mm driving from TTP224 IC on my PCB. There will be 2mm glass panel above Touch pads. My PCB contains other circuits like Arduino, Antenna bands and driving LED's as well along with these touch pads. These 4 touch pads are at different positions (They are not side by side).

  • Will the tracks (Track width:10 mils) from touch pads to the TTP224 IC when touched will detect the touch or only touch pads will detect the touch? (I don't want tracks to detect the touch).

  • Can I place common copper ground pour on PCB's opposite layer of that of touch pads?

  • Can I place Antenna bands (of Bluetooth/WiFi) on PCB's opposite layer of that of touch pads?

  • Can I place any other IC's or components (Like TTP224, RC's etc.) on PCB's opposite layer of that of touch pads?

  • What maximum diameter I can take as touch pads?

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  • \$\begingroup\$ Because of the solder mask on the tracks you will not be able to touch them methinks \$\endgroup\$
    – Ananas_hoi
    Commented Jan 27, 2021 at 7:34
  • \$\begingroup\$ @Ananas_hoi I've kept solder mask above touch pads also and there will be 2mm glass above PCB through which I need to sense touch. And I've tested TTP224 module's sensitivity that above 2mm of PCB I'm able to detect the touch. That's why I think in my new design my tracks would also sense touch which is false touch for me? \$\endgroup\$
    – saurabh kandalkar
    Commented Jan 27, 2021 at 9:28
  • \$\begingroup\$ Makes sense, disregard my first comment. The best thing you could do is lay the tracks away from the finger, so on the back layer. Also make the tracks as thin as your pcb manufacturer allows. Lastly, the capacitance of the tracks is determined by dielectric, if you can choose choose a board with a low dielectric constant (and if your design allows cover the tracks where they will be touched with low-constant material. \$\endgroup\$
    – Ananas_hoi
    Commented Jan 27, 2021 at 11:21

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  1. If you do the touch only from touch pad than you should minimize the track width to 0.17 mm, and track should be surrounded by hatched ground plane.

  2. Yes, you should place the ground plane on opposite side plane.

  3. You should place on opposite side but some far away from touch track.

  4. It depends on the where you place touch and thickness of the backend material?

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