0 Replies Latest reply on Jan 10, 2019 12:47 AM by PaAr_3783191

    [How to] Capacitive Touch Sensor StackUp Guide

    PaAr_3783191

      Everything you Need to Know about the Structure and Functionality of a PCAP Touch Sensor StackUp.

       

      1) Common electrode patterns

      2) Relevant to touch sensor design abbreviations/acronyms

      3) Examples of the most common stackup configurations

       

      Each touch sensor features 2 sets of electrodes: the Transmitting ones (also known as Tx, or the driving electrodes, or simply X electrodes) and the Receiving ones (also known as Rx, or the sensing electrodes or simply Y electrodes).

       

      Electrodes are usually made of Indium Tin Oxide, also known as ITO. However, during the last years, ITO alternatives have gained momentum and this trend is expected to continue in the years to come.

       

      The most popular ITO alternative is Metal Mesh. Carbon nanotubes, PEDOT, copper mesh and silver nanowires are promising technologies that have emerged recently and

      show potential in replacing ITO too.

       

      When selecting electrode material, there are 3 major things to consider:

       

      Resistance of the material: ITO has a resistance  of about 100 ohms/square, while metal mesh has 10-30 ohms/ square.

       

      Optical transmission of the material: Non index-matched ΙΤΟ has a 90-95% light transmittance rate, while silver nanowires more than 94%.

       

      Design of the sensor itself: If it’s a large or a bent sensor, then ITO might not be preferred. These two design trends are those that have paved the way for ITO

      alternatives.

       

      ITO has high sheet resistance.The sheet resistance affects the charge time of the sensor and it’s proportional to its size. That’s why ITO is not favored in large touch sensors.

       

      Bent touch sensors require the electrodes to be bent too (not just the cover glass). That’s where another drawback of ITO is evident: ITO breaks easily when bent, while its alternatives, e.g. metal mesh can be bent to a radius of up to 4mm without breaking.

       

      You can read more here.