Vibrating Device Ion Migration Drift Reduction

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Solution Overview

Problem

Acceleration sensors with glass substrates containing mobile ions, such as sodium ions, face issues with output drift due to electrostatic attraction caused by ion migration under applied voltages, leading to inaccurate acceleration detection.

Innovation Solution

A vibrating device configuration with a base body containing mobile ions, a movable member, and a conductor section where a first voltage with a periodically changing potential is applied to the movable member, and a second voltage at a constant reference potential is applied to the conductor section, reducing ion migration and electrostatic attraction.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Strength

If a glass substrate containing mobile ions (such as sodium ions) is used, then the glass substrate can be bonded to the silicon substrate and provide structural support, but the mobile ions migrate due to applied voltage causing electrostatic attraction and output drift

Engineering Contradiction:

Improvebonding strengthVSAvoidoutput drift

Core Design Contradiction:

StrengthVSReliability

Solution Approach 1:

An insulating layer (such as silicon oxide or silicon nitride) is introduced between the glass substrate and the movable electrode to prevent mobile ions from reaching the electrode. This intermediary layer blocks ion migration while maintaining the structural integrity and bonding strength of the glass substrate, thereby eliminating output drift without sacrificing mechanical strength.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Measurement precision

If a voltage is applied to the fixed electrode to detect acceleration, then acceleration detection is enabled, but mobile ions migrate causing electrostatic attraction between the glass substrate and the beam

Engineering Contradiction:

Improveacceleration detectionVSAvoidelectrostatic attraction

Core Design Contradiction:

Measurement precisionVSObject-affected harmful factors

Solution Approach 1:

The insulating layer serves as a mediator that allows the electric field necessary for acceleration detection to pass through while blocking the physical migration of mobile ions. This enables the fixed electrode to function for capacitance-based acceleration sensing without causing ion migration and subsequent electrostatic attraction to the movable beam.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The harmful mobile ions are effectively removed from the interaction zone between the electric field and the movable beam by the insulating layer. This extraction of the problematic component (mobile ions) from the detection mechanism allows clean capacitance measurement without electrostatic attraction effects.

Inventive Principle:

Principle #2Taking out (Extraction)

3Force

If the surface of the glass substrate becomes charged due to ion migration, then electrostatic attraction occurs, but this causes the movable electrode to be attracted toward the glass substrate without acceleration application

Engineering Contradiction:

Improveelectrostatic attractionVSAvoidoutput signal drift

Core Design Contradiction:

ForceVSMeasurement precision

Solution Approach 1:

The insulating layer prevents mobile ions from reaching the movable electrode and accumulating on the glass substrate surface. By blocking ion transport, this intermediary layer eliminates the charging effect that would otherwise create spurious electrostatic attraction forces and output signal drift during operation.

Inventive Principle:

Principle #24Intermediary (Mediator)

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 effectively reduces output drift and enhances the accuracy of acceleration detection by minimizing ion migration and electrostatic interactions between the base body and the movable member.

Implementation Method 1

the mobile ions in the glass substrate migrate due to a voltage applied to the fixed electrode

Methodology Applied

Scientific EffectIon migration: Electrophoresis

Implementation Method 2

the charging of the surface of the glass substrate on the side facing the silicon substrate can cause electrostatic attraction between the glass substrate and the beam

Methodology Applied

Scientific EffectElectrostatic attraction: Electrostatics

Implementation Method 3

A capacitance is generated between the movable electrode and the fixed electrode. When the movable electrode is displaced with respect to the glass substrate upon the application of acceleration, a gap dimension between the movable electrode and the fixed electrode is changed. In response to this displacement, the capacitance generated between the movable electrode and the fixed electrode changes

Methodology Applied

Scientific EffectCapacitance: Capacitance

Data Source

PatentUS11137415B2Vibrating device, vibrating device module, electronic apparatus, and vehicle

Publication Date: 2021.10.05 SEIKO EPSON CORP

AI summary

A vibrating device includes: a base body containing mobile ions; a movable member disposed facing and spaced apart from the base body; and a conductor section disposed so as to cover at least a portion of the movable member. A first voltage whose potential periodically changes based on a reference potential is applied to the movable member. A second voltage that is at the reference potential when time-averaged is applied to the conductor section. The second voltage is constant at the reference potential.