Pressure Sensor Linearization via Segmented Electrodes

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Solution Overview

Problem

Existing touch-mode pressure sensors with recessed dielectric layers suffer from variations in processing, leading to non-linear changes in electrostatic capacitance and reduced measurement accuracy due to inconsistencies in the depth and smoothness of the recessed portion.

Innovation Solution

A pressure sensor device with multiple fixed electrodes, including a central and outer ring-shaped electrode, and a sensor controller that divides the pressure measurement range into segments, using correction formulas specific to each segment to ensure linear changes in electrostatic capacitance, eliminating the need for a recessed dielectric layer.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If a recessed portion is formed in the dielectric layer to improve linearity of electrostatic capacitance changes, then measurement accuracy is improved, but manufacturing precision deteriorates due to processing variations in the recessed portion

Engineering Contradiction:

Improvepressure measurement accuracyVSAvoidrecessed portion depth and smoothness consistency

Core Design Contradiction:

Measurement precisionVSManufacturing precision

Solution Approach 1:

The invention extracts and eliminates the problematic recessed portion from the dielectric layer. Instead of forming a recessed portion in the dielectric layer, the patent uses a flat dielectric layer combined with a protruding portion on the fixed electrode that extends into the gap between the membrane and dielectric layer. This extraction of the recessed portion structure resolves the manufacturing precision issues while maintaining the electrical field concentration effect needed for linear capacitance changes.

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

Instead of creating a recessed portion in the dielectric layer to concentrate the electrical field, the invention inverts the approach by creating a protruding portion on the fixed electrode that extends upward into the gap. This inverted structure achieves the same field concentration effect without the manufacturing difficulties of forming recesses in the dielectric layer, thereby improving both linearity and manufacturing precision.

Inventive Principle:

Principle #13The other way round (Inversion)

2Measurement precision

If multiple fixed electrodes are used to improve linearity across the entire pressure range, then measurement accuracy is improved, but device complexity increases

Engineering Contradiction:

Improvelinearity of electrostatic capacitance changesVSAvoidnumber of fixed electrodes and correction formulas

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The invention divides the pressure measurement range into multiple pressure segments, with each fixed electrode responsible for a specific segment. The central fixed electrode handles lower pressure ranges while outer fixed electrodes handle higher pressure ranges. This segmentation allows each electrode to operate in its optimal range, maintaining linearity across the entire pressure spectrum while providing a systematic approach to managing complexity through modular design.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Different fixed electrodes are positioned at different locations (central and outer regions) with different structural characteristics. Each electrode has optimized properties for its specific operational range, with the central electrode having different dimensions and positioning compared to the outer electrodes. This local optimization ensures that each electrode contributes maximally to linearity in its designated pressure segment.

Inventive Principle:

Principle #3Local quality

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 approach achieves high accuracy in pressure measurement by ensuring desired linearity of electrostatic capacitance changes across the entire pressure range, improving measurement precision without the variability associated with recessed dielectric layers.

Implementation Method 1

a membrane that is conductive and deformable under pressure

Methodology Applied

Scientific EffectElastic deformation: Elasticity

Implementation Method 2

the electrostatic capacitance between the membrane and the fixed electrode is increased by a decrease in the distance between the membrane and the dielectric layer

Methodology Applied

Scientific EffectElectrostatic capacitance: Capacitance

Implementation Method 3

a dielectric film disposed on the electrode surface of each of the plurality of fixed electrodes

Methodology Applied

Scientific EffectDielectric property: Dielectric

Data Source

PatentUS11280692B2Pressure sensor device and pressure sensor module including same

Publication Date: 2022.03.22 MURATA MFG CO LTD

AI summary

A pressure sensor device in a pressure sensor module includes a membrane that is conductive and deformable under pressure, fixed electrodes each including an electrode surface opposed to the membrane, and a dielectric film disposed on the electrode surface of each of the fixed electrodes. The fixed electrodes are disposed in a direction from the center of the membrane toward an outer portion.