Touch Sensor Electrode Layout for Noise Reduction
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Solution Overview
Problem
Touch sensors on display devices are vulnerable to noise interference and require complex bonding processes, affecting recognition sensitivity and rate, especially in single-sided ITO structures, and are cumbersome in double-sided ITO configurations.
Innovation Solution
A touch sensor design with transmitter and receiver electrode layers on opposite surfaces of a substrate, using a polarizing plate as a substrate, and pads positioned to facilitate a single bonding process with a flexible printed circuit board, enhancing noise robustness and simplifying the bonding process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If transmitter and receiver touch sensing electrodes are formed on the same surface of the substrate (single-sided ITO structure), then device complexity is reduced, but noise interference increases and recognition sensitivity deteriorates
Solution Approach 1:
The touch sensor is segmented into two separate electrode layers positioned on opposite surfaces of the substrate. The transmitter electrode layer is formed on the first surface while the receiver electrode layer is formed on the second surface, physically separating the two functions to eliminate mutual interference and improve noise robustness.
Solution Approach 2:
The electrode arrangement transitions from a two-dimensional planar configuration (both electrodes on the same surface) to a three-dimensional stacked configuration (electrodes on opposite surfaces). This dimensional change allows the transmitter and receiver electrodes to be spatially separated while maintaining electrical functionality, thereby reducing noise interference.
2Reliability
If transmitter and receiver touch sensing electrodes are formed on both sides of the substrate (double-sided ITO structure), then noise robustness is improved, but manufacturing complexity increases due to requiring two bonding processes
Solution Approach 1:
The bonding processes for the transmitter and receiver electrode layers are merged into a single simultaneous bonding operation. Both electrode layers are bonded to the FPCB at the same time using one bonding tool, reducing the total number of bonding processes from two to one while maintaining the dual-sided electrode structure.
Solution Approach 2:
The FPCB is designed with universal bonding capability to connect to both the transmitter and receiver electrode layers simultaneously. The FPCB serves multiple functions by providing electrical connections to both electrode types in a single bonding operation, simplifying the manufacturing process.
3Productivity
If pads are positioned to facilitate single bonding process, then manufacturing efficiency is improved, but pad layout complexity increases
Solution Approach 1:
The pad layout employs asymmetric positioning where the first pad is located at a first position on the first electrode layer and the second pad is located at a second position on the second electrode layer. This asymmetric arrangement optimizes the bonding geometry to enable simultaneous bonding while managing the inherent layout complexity.
Data Source
AI summary
A touch sensor includes a substrate and first and second touch sensor electrode layers. The first touch sensor electrode layer is disposed on a first surface of the substrate, and includes a first pad formed on an opposing surface to a surface in contact with the substrate. The second touch sensor electrode layer is disposed on a second surface of the substrate, exposes at least a portion of the surface in contact with the substrate to an outside of the substrate, and includes a second pad formed on the portion exposed to the outside of the surface in contact with the substrate. The first pad and the second pad do not overlap in a stacking direction.