Capacitive Sensor Decoupling Galvanic Connections
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Solution Overview
Problem
Conventional MEMS accelerometers require complex fabrication processes and additional conducting layers for galvanic connections, leading to increased fabrication costs and planarization problems, especially when measuring high-G accelerations.
Innovation Solution
A capacitive sensor device with a movable element decoupled from the substrate, eliminating the need for galvanic connections and additional conducting layers, utilizing a simple planar layout with capacitors connected in series or parallel for improved measurement sensitivity and reduced fabrication steps.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If galvanic connections and additional conducting layers are used for measuring high-G accelerations, then measurement capability is improved, but fabrication complexity and costs increase
Solution Approach 1:
The patent extracts and eliminates the galvanic connection requirement from the accelerometer design. By using a capacitive sensing approach where the movable mass is electrically isolated from the substrate, the invention removes the need for additional conducting layers and complex galvanic connection fabrication, thereby reducing device complexity while maintaining high-G measurement capability
Solution Approach 2:
The patent replaces the mechanical/electrical galvanic connection system with a capacitive coupling system. Instead of using physical conducting layers to connect the movable mass to readout circuits, the invention uses capacitive coupling through the substrate, substituting a simpler fabrication process for the complex multi-layer conducting structure
2Reliability
If galvanic connections are implemented, then electrical connection reliability is improved, but planarization problems and fabrication difficulty increase
Solution Approach 1:
The patent substitutes the mechanical galvanic connection system with a capacitive coupling mechanism. The movable mass remains electrically isolated from the substrate, and electrical signals are transmitted through capacitive coupling rather than physical conducting layers, eliminating planarization problems while maintaining reliable signal transmission
Solution Approach 2:
The substrate serves multiple functions: it provides mechanical support for the movable mass, acts as a capacitor dielectric for signal coupling, and eliminates the need for separate conducting layers. This multi-functionality simplifies fabrication while maintaining electrical connection reliability
3Measurement precision
If complex fabrication processes with additional conducting layers are used, then measurement accuracy is improved, but manufacturing costs increase
Solution Approach 1:
The patent extracts and removes the expensive additional conducting layers from the fabrication process. By using capacitive coupling through the existing substrate, the invention eliminates material and processing costs associated with depositing and patterning multiple conducting layers, thereby reducing manufacturing costs while preserving measurement accuracy
Solution Approach 2:
The patent changes the electrical coupling parameter from galvanic (direct conductive connection) to capacitive (electric field coupling). This parameter change allows the use of standard substrate materials and simplified fabrication processes, reducing manufacturing costs while maintaining the ability to accurately measure accelerations
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
Enables efficient measurement of high-G accelerations with reduced fabrication complexity and costs, filtering out small accelerations and fabrication mismatches, while providing a non-linear response for accurate high-acceleration detection.
Implementation Method 1
the movable element is capacitively coupled to the first electrode, the movable element and the first electrode representing a first capacitor. The movable element is capacitively coupled to the second electrode, the movable element and the second electrode representing a second capacitor
Implementation Method 2
The movable element is elastically connected to the substrate by a spring element
Implementation Method 3
the force F on the mass due to an acceleration a is given by F=M·a
Data Source
AI summary
The invention relates to a capacitive sensor device 100. The capacitive sensor device (100) comprises a substrate (401), a first electrode (101) coupled to the substrate (401, a second electrode (102) coupled to the substrate (401) and a movable element (103). The movable element (103) is capacitively coupled to the first electrode (101), the moveable element (103) and the first electrode (101) representing a first capacitor (104). The movable element (103) is capacitively coupled to the second electrode (102), the moveable element (103) and the second electrode (102) representing a second capacitor (105). The movable element (103) is movable between the first electrode (101) and the second electrode (102) in such a manner, that an electrical impedance between the first electrode (101) and the second electrode (102) is changeable due to a change of a position of the movable element (103). The movable element (103) is decoupled from the substrate (401), in particular to a signal line.