Interdigitated Capacitive Sense Array for Narrow Bezel Integration
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Solution Overview
Problem
The challenge in touch display screens is fitting a large number of capacitive sense array interconnects within a narrow bezel, which is exacerbated by the need to wire capacitive sense elements to an edge area, especially in devices with high aspect ratios and limited bezel width.
Innovation Solution
A capacitive sense array is reconfigured with interdigitated column electrodes and reduced row interconnects, allowing the interconnects to fit within a narrower bezel by using a two-layer mutual capacitance sensor design, where each capacitive sense element is formed by the intersection of a row and column electrode, and routing traces are strategically placed to access these electrodes from the edges, reducing the number of row interconnects required.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the resolution of the capacitive sense array is substantially large, then the touch detection precision is improved, but the number of wires required to access the electrical circuit increases, making it difficult to fit within the narrow bezel
Solution Approach 1:
The capacitive sense array is segmented into multiple regions with different electrode configurations. The first region uses a conventional grid pattern, while the second region uses shared row electrodes that are selectively activated. This segmentation allows high-resolution touch detection in the first region while reducing the number of physical wires needed in the second region, as multiple sense elements share common row electrode connections.
Solution Approach 2:
The row electrodes are designed to serve multiple functions: they act as drive electrodes for active rows and as shared sense electrodes for inactive rows. This multi-functionality allows the same physical electrode structure to support both high-resolution touch detection and reduced wire count, as the same row electrodes can be reused across multiple columns through selective activation schemes.
2Ease of manufacture
If the number of routing traces is reduced to fit within the narrow bezel, then the ease of manufacture is improved, but the number of accessible electrodes is reduced
Solution Approach 1:
The patent introduces a temporal dimension to the electrode access problem by implementing selective row activation. Instead of requiring all row electrodes to be simultaneously accessible through separate physical traces, the system activates rows sequentially or selectively based on touch detection needs. This allows the same physical routing infrastructure to support more logical electrode connections by reusing traces across different time periods or operational modes.
Solution Approach 2:
The system dynamically changes the electrical state parameters of the row electrodes, switching them between drive mode and sense mode, and between active and inactive states. This parameter changing allows a reduced set of physical electrodes to effectively control a larger number of sense elements, as the same electrode can serve different functional roles at different times, thereby maintaining electrode accessibility without increasing the physical wire count.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This configuration allows for effective touch detection and tracking within a bezel-less or nearly bezel-less display, maintaining interconnect quality and yield while accommodating higher aspect ratios and smaller bezel widths, enhancing the usability of touch-sensitive displays in modern devices.
Implementation Method 1
Self or mutual capacitance associated with a capacitive sense element varies when a conductive object (e.g., a finger, hand, or other object) comes into contact or close proximity with the capacitive sense element. The electrical circuit coupled to the capacitive sense array is configured to measure the capacitance of individual capacitive sense elements and to look for a variation of capacitance indicating a touch or presence of the conductive object.
Data Source
AI summary
This application is directed to a capacitive sense array including a two-dimensional array of capacitive sense elements. Each capacitive sense element is formed by a respective intersection of (i) a respective row electrode in a first electrode layer and (ii) a respective column electrode in a second electrode layer. Each column of the capacitive sense elements includes two or more interdigitated column electrodes. Each row electrode forms two or more rows of capacitive sense elements at intersections with the column electrodes.