Metal Mesh Projected-Capacitive Touch Screens Simulated with Fieldscale SENSE
CASES SOLVED WITH SENSE
Indium Tin Oxide (ITO) VS Metal Mesh in Mutual-Capacitive Touch Sensors
Sensor electrodes are typically made of Indium Tin Oxide (ITO) due to its high optical transmittance.
Although widely used, ITO is nowadays losing ground to alternatives, due to the following disadvantages:
- limited supply
- considerable cost
- inflexibility, not suitable for wearables and flexible touch screens
- high resistivity, slow response; not suitable for large touch screens
Metal Mesh; ITO alternative
Metal Mesh patterns advantages:
- flexibility
- low resistivity
- high optical transmission
- low cost
Metal Mesh patterns are difficult to simulate
because of:
- complicated geometry
- huge aspect ratios
Simulation with SENSE
In this use case, we researched the following:
- influence of line width
- influence of line pitch
- influence of cover glass thickness
- influence of cover glass permittivity
in mutual capacitance response.
Conclusions
As metal mesh becomes more coarse:
- optical transmission increases.
- ΔCm/Cm0 increases: the touch sensor becomes more sensitive.
- but RC constant increases: the touch sensor has slower response