Touchpad Electrode Layout for Shielding Without Extra Layers
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Solution Overview
Problem
Existing touchpad designs with complex applications like pressure-sensitive haptic feedback require additional layers to maintain shielding, increasing cost and affecting touch performance, especially when using BGA packaging components with many pins.
Innovation Solution
A sensing touchpad architecture with a substrate and multiple layers, including first and second driving electrodes, sensing electrodes, and ground elements, where the second driving electrodes and ground elements are positioned in different layers to enhance shielding without increasing layer count, using conductive elements to connect them.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If the number of layers is increased to maintain shielding effect, then shielding effectiveness is improved, but manufacturing cost increases and device complexity increases
Solution Approach 1:
The patent transitions from a planar arrangement of electrodes and ground layers to a three-dimensional stacked architecture. Ground elements are positioned at multiple vertical levels (first ground elements below first driving electrodes, second ground elements above second driving electrodes), creating a volumetric shielding structure that enhances electromagnetic shielding without requiring additional lateral layers. This vertical dimensionality change allows comprehensive shielding while maintaining a compact layer count.
Solution Approach 2:
The patent implements a nested configuration where ground elements are interleaved with driving electrodes in alternating layers. The first ground elements are nested below the first driving electrodes, while second ground elements are nested above the second driving electrodes. This nested arrangement creates multiple shielding zones within the same vertical space, enhancing shielding effectiveness without increasing the overall number of layers.
2Adaptability or versatility
If BGA packaging components with large quantity of pins are used, then functionality is improved, but ground shielding layer completeness deteriorates due to numerous blind vias
Solution Approach 1:
The patent applies different ground element configurations in different spatial zones. First ground elements are positioned in regions where BGA blind vias are present to provide localized shielding beneath the BGA component. Second ground elements are positioned in other regions to maintain overall shielding continuity. This localized adaptation allows the shielding structure to accommodate BGA packaging requirements while maintaining shielding effectiveness in critical areas.
Solution Approach 2:
Instead of relying solely on a continuous planar ground layer that is disrupted by BGA vias, the patent creates a three-dimensional shielding network with ground elements at multiple vertical levels. This volumetric approach compensates for the discontinuities introduced by blind vias, as the stacked ground elements provide alternative shielding paths that bypass the via-induced gaps in the traditional ground plane.
3Device complexity
If driving electrodes and sensing electrodes are placed in the same layer, then device complexity is reduced, but additional bridge through holes are required interconnecting driving electrodes
Solution Approach 1:
The patent segments the driving electrodes into separate groups positioned in different layers. First driving electrodes are placed in a first layer, while second driving electrodes are placed in a second layer. This segmentation eliminates the need for bridge through holes to interconnect driving electrodes within the same layer, as each layer's driving electrodes can be independently routed and connected to their respective readout circuits without crossing other electrode traces.
Solution Approach 2:
The patent resolves the routing conflict by transitioning from a two-dimensional planar arrangement to a three-dimensional stacked configuration. Driving electrodes that would require bridge through holes in a single layer are instead distributed across multiple vertical layers. This spatial separation in the vertical dimension allows independent routing of each driving electrode group without the need for inter-layer connections via bridge holes, simplifying the overall interconnect structure.
Data Source
AI summary
A sensing touchpad includes a substrate, a plurality of first driving electrodes, a plurality of sensing electrodes, at least one second driving electrode and at least one ground element. The substrate has a first surface and a second surface opposite to each other. The plurality of first driving electrodes are arranged in a first layer on the top surface of the substrate. The plurality of sensing electrodes are arranged in a second layer on the first layer. The at least one second driving electrode is arranged in the second layer. The at least one ground element is arranged in the first layer, and the at least one ground element overlaps with the at least one second driving electrode on a normal direction of the substrate.