[How to] The Ultimate Touch Sensor StackUp Guide (part 2)

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The touch sensor industry can seem a bit overwhelming and confusing to a newcomer. A lot of different types of sensor configurations, many materials used and tons of jargon.

With capacitive sensing undergoing such a rapid growth and penetrating more and more industries, it attracts the interest of many engineers with little to none experience with it.

That’s why we have created this guide. It provides you with insights on the anatomy of a capacitive touch sensor and industry terms, including:

 

Part I: (you can get it here for free)
Common stackup components
Attributes of common materials in the stackup

 

Part II: 
Common electrode patterns
Relevant to touch sensor design
abbreviations/acronyms
Examples of the most common stackup configurations

 

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:

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

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

3) 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).

 

You can get the whole guide for free here.