Piezoelectric Vibrator Stray Capacitance Suppression

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Solution Overview

Problem

Piezoelectric vibrators face challenges in achieving large electrostatic capacity while minimizing the influence of stray capacitance, particularly in MEMS vibrators with configurations that either result in reduced capacitance or increased resonant impedance due to stray capacitance issues.

Innovation Solution

A piezoelectric vibrator design featuring vibration members with silicon layers, piezoelectric layers, and electrodes configured such that the first and second piezoelectric layers have opposite polarization directions, and electrodes are connected in a manner that allows for large electrostatic capacity and suppresses stray capacitance by eliminating the need for insulation layers between silicon and lower electrodes.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Quantity of substance

If a parallel connection configuration is used to increase electrostatic capacity, then combined capacitance increases, but stray capacitance is generated due to short-circuiting of lower electrodes through the silicon layer

Engineering Contradiction:

Improveelectrostatic capacityVSAvoidstray capacitance

Core Design Contradiction:

Quantity of substanceVSObject-generated harmful factors

Solution Approach 1:

An insulation layer is introduced as an intermediary between the lower electrodes and the silicon layer. This mediator prevents direct electrical contact (short-circuit) between lower electrodes while allowing the electrodes to maintain their positioning function, thus eliminating stray capacitance generation while preserving the parallel connection configuration's electrostatic capacity advantage

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The lower electrodes are segmented into electrically isolated units by the insulation layer. Instead of having continuous conductive paths through the silicon layer, the insulation layer divides the lower electrode structure into separate segments that cannot short-circuit, thereby preventing stray capacitance while maintaining individual electrode functionality

Inventive Principle:

Principle #1Segmentation

2Object-generated harmful factors

If a series connection configuration is used to eliminate stray capacitance, then stray capacitance influence is reduced, but combined capacitance decreases and resonant impedance increases

Engineering Contradiction:

Improvestray capacitanceVSAvoidelectrostatic capacity

Core Design Contradiction:

Object-generated harmful factorsVSQuantity of substance

Solution Approach 1:

Instead of using series connection to eliminate stray capacitance (which reduces capacitance), the invention inverts the approach by using parallel connection combined with an insulation layer. This reversal maintains high capacitance while achieving stray capacitance elimination through the insulating barrier between lower electrodes

Inventive Principle:

Principle #13The other way round (Inversion)

3Object-generated harmful factors

If an insulation layer is added to prevent short-circuiting of lower electrodes, then stray capacitance is suppressed, but device complexity increases

Engineering Contradiction:

Improvestray capacitanceVSAvoidstructure complexity

Core Design Contradiction:

Object-generated harmful factorsVSDevice complexity

Solution Approach 1:

The insulation layer serves multiple functions simultaneously: it prevents short-circuiting between lower electrodes, suppresses stray capacitance, and maintains the mechanical positioning of electrodes. By combining multiple functions into a single component, the actual complexity increase is minimized while achieving comprehensive stray capacitance suppression

Inventive Principle:

Principle #6Universality (Multi-functionality)

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

The design achieves a larger electrostatic capacity and improved vibration performance by eliminating stray capacitance, enhancing the characteristics of piezoelectric vibrators compared to typical configurations.

Implementation Method 1

each of the first and second vibration members includes a silicon layer, a first piezoelectric layer disposed on the silicon layer, a first electrode disposed on the first piezoelectric layer, a second piezoelectric layer that is disposed on the first electrode and has polarization in an opposite direction to a direction of polarization of the first piezoelectric layer

Methodology Applied

Scientific EffectPiezoelectric effect: Piezoelectric Effect

Data Source

PatentUS10224896B2Piezoelectric vibrator and piezoelectric vibration device

Publication Date: 2019.03.05 MURATA MFG CO LTD

AI summary

A piezoelectric vibrator that includes first and second vibration portions that vibrate with mutually reverse phases. Each of the vibration portions includes a silicon layer, a first piezoelectric layer and a second piezoelectric layer that has polarization in an opposite direction to a direction of polarization of the first piezoelectric layer. First and second electrodes are disposed on opposite sides of the second piezoelectric layer. The piezoelectric vibrator has a structure such that a first potential is applied to the first electrode of the first vibration portion and the second electrode of the second vibration portion, and a second potential is applied to the second electrode of the first vibration portion and the first electrode of the second vibration portion.