Capacitive Touch Sensor Bridge Pattern for RC Time-Constant Matching
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Large projected capacitive touch sensors face issues with high resistor-capacitor time constants (RCtc) due to mismatched RCtc values between horizontally and vertically arranged electrodes, leading to prolonged electronic settling times and impacting user experience, especially in larger displays.
Innovation Solution
The use of asymmetric bridge patterns with varying dimensions for channels and links connecting electrode pads allows for the reduction and matching of RCtc values between horizontally and vertically arranged electrodes, facilitating faster touch location acquisition.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If symmetric square bridge connections are used to connect electrode pads, then the structure is simple and easy to manufacture, but the RCtc values of horizontally and vertically arranged electrodes do not match, leading to prolonged electronic settling times
Solution Approach 1:
The patent applies asymmetry by designing bridge connections with different geometries for horizontal and vertical electrode orientations. Specifically, horizontal bridges have different dimensions (width, length, orientation) compared to vertical bridges, allowing each to be optimized for its specific RCtc characteristics. This asymmetric design enables matching of RCtc values between horizontally and vertically arranged electrodes, thereby reducing electronic settling times while maintaining manufacturability through systematic geometric variation.
2Area of stationary object
If the touch sensor size is increased for larger displays, then the display area is improved, but the RCtc values increase quadratically, causing longer settling times and impacting user experience
Solution Approach 1:
The patent applies local quality by optimizing bridge connection parameters locally for different regions and orientations within the touch sensor. Instead of using uniform bridge designs across the entire sensor, the invention tailors bridge dimensions, shapes, and configurations to specific local requirements. This allows larger touch sensors to maintain matched RCtc values across different electrode orientations and regions, preventing quadratic growth of settling times as sensor area increases.
Solution Approach 2:
The patent employs parameter changes by systematically varying bridge connection parameters (width, length, orientation, shape) to compensate for the quadratic increase in RCtc values that occurs with larger sensor sizes. By adjusting these geometric parameters, the invention maintains optimal RCtc matching even as the overall sensor dimensions increase for larger displays, thereby preserving fast electronic settling times across different display sizes.
3Device complexity
If fixed drive frequency controllers are used with large touch sensors, then the control logic is simple, but the high RCtc values require longer scan times, reducing touch location determination rate
Solution Approach 1:
The asymmetric bridge design enables balanced RCtc characteristics between horizontal and vertical electrodes, which allows fixed drive frequency controllers to operate more efficiently. By ensuring that both electrode orientations have matched and minimized RCtc values, the system achieves faster overall scan times without requiring complex adaptive control logic, thus maintaining simple controller design while improving touch location determination rate.
Data Source
Figure 1~2
Figure 3A~3C
Figure 4A~4B
AI summary
A capacitive touch sensitive device includes a matrix of pads patterned in a first electrically conductive material on a substrate. Horizontally adjacent pads within each even row of the matrix are electrically coupled to one another via channels to form a plurality of horizontally arranged electrodes. Insulators are positioned over respective channels. Conductive links are formed over respective insulators and are configured to electrically couple vertically adjacent pads between odd rows of the matrix to form a plurality of vertically arranged electrodes. The dimensions of the channels and the conductive links are configured such that an RC time-constant (RCtc) of each of the vertically arranged electrodes substantially matches an RCtc of each of the horizontally arranged electrodes.