Touchpad Electrode Layout for Shielding in BGA Integration
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Solution Overview
Problem
Existing touchpad designs with complex applications, such as pressure-sensitive haptic feedback, require additional layers to maintain shielding effects for driving electrodes, increasing cost and affecting touch performance, especially when using components with a large number of pins like BGA packaging.
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 the number of layers, 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 for driving electrodes, 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 to a three-dimensional stacked architecture where driving electrodes and sensing electrodes are arranged in alternating layers. This vertical stacking enables shielding functionality without proportionally increasing the horizontal footprint or overall layer count, as the shielding ground electrodes are integrated into the same stack structure rather than requiring separate dedicated shielding layers.
Solution Approach 2:
The patent implements nested functionality where ground shielding electrodes are positioned between driving and sensing electrodes within the same layer stack. The shielding function is nested within the existing electrode structure rather than requiring additional external shielding layers, thus maintaining compactness while providing effective electromagnetic shielding.
2Adaptability or versatility
If BGA packaged components with large quantity of pins are used, then functionality and integration are improved, but the ground shielding layer becomes incomplete due to numerous blind vias, losing shielding effect
Solution Approach 1:
The patent applies local quality by positioning ground shielding electrodes specifically in regions where shielding is most critical - between the driving electrodes and sensing electrodes - rather than requiring a complete continuous ground layer throughout the entire substrate. This localized shielding approach maintains effectiveness while accommodating BGA component vias.
Solution Approach 2:
The patent segments the shielding function into multiple discrete ground electrodes distributed throughout the layer stack, rather than relying on a single continuous ground layer. This segmentation allows the shielding function to be maintained even when individual ground electrode regions are interrupted by blind vias for BGA components, as adjacent ground segments provide continuous shielding coverage.
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 to interconnect driving electrodes
Solution Approach 1:
The patent resolves the interconnection problem by moving from a two-dimensional planar interconnection approach to a three-dimensional vertical stacking approach. Driving electrodes and sensing electrodes are separated into different layers along the vertical dimension, allowing each electrode type to be continuously patterned without requiring bridge through-holes to cross over other electrodes, thus simplifying manufacturing while maintaining low layer count.
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.