Piezoelectric Vibrator Connection Alteration for Precise Frequency Tuning

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Solution Overview

Problem

Existing frequency adjustment methods for piezoelectric vibrators face issues such as residual substance generation, instability in frequency characteristics, risk of short circuits, and reduced Q-value due to laser irradiation, and increased package size from projections, while altering layers can weaken vibration arms, especially under large amplitude driving.

Innovation Solution

A piezoelectric vibrator with a single crystal vibration arm and a connection portion that includes an alteration portion formed inside by laser irradiation, preventing surface effects and maintaining strength, allowing precise frequency adjustment without residual substances or electrode scattering.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Manufacturing precision

If laser irradiation is applied to remove mass film for frequency adjustment, then frequency adjustment is achieved, but residual substance is generated and Q-value is lowered

Engineering Contradiction:

Improvefrequency adjustment precisionVSAvoidresidual substance generation

Core Design Contradiction:

Manufacturing precisionVSObject-generated harmful factors

Solution Approach 1:

An alteration layer is introduced as an intermediary between the laser irradiation process and the vibration arm surface. This alteration layer absorbs the harmful effects of laser irradiation, preventing direct interaction between the laser and the vibration arm, thereby eliminating residual substance generation while maintaining frequency adjustment capability

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The invention converts the harmful laser irradiation into a beneficial process by using it to create an alteration layer with specific properties. This alteration layer, while initially seeming to add complexity, actually protects the vibration arm from direct laser damage and prevents residual substance formation, turning a harmful process into a protective mechanism

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

2Manufacturing precision

If alteration layer is provided in vibration arm for frequency adjustment, then secondary mode is suppressed, but strength of vibration arm is lowered

Engineering Contradiction:

Improvefrequency adjustment precisionVSAvoidvibration arm strength

Core Design Contradiction:

Manufacturing precisionVSStrength

Solution Approach 1:

The alteration layer is applied locally only in the connection portion where it is most needed for frequency adjustment and secondary mode suppression, rather than throughout the entire vibration arm. This localized application minimizes the impact on overall strength while achieving the desired frequency control

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The invention carefully controls the parameters of the alteration layer, including its thickness (0.4 to 0.6 times the vibration arm length) and formation conditions, to achieve optimal frequency adjustment while minimizing strength reduction. By precisely controlling these parameters, the alteration layer provides necessary frequency control with minimal impact on mechanical properties

Inventive Principle:

Principle #35Parameter changes

3Reliability

If projection is provided on inner wall of package to prevent film reattachment, then film reattachment is prevented, but package height increases

Engineering Contradiction:

Improvefrequency stabilityVSAvoidpackage height

Core Design Contradiction:

ReliabilityVSLength of stationary object

Solution Approach 1:

The invention extracts the frequency stability function from the package structure by using an alteration layer on the vibration arm itself, rather than requiring additional package features like projections. This separates the frequency control function from the package design, maintaining reliability without increasing package dimensions

Inventive Principle:

Principle #2Taking out (Extraction)

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 high-precision frequency adjustment with minimal strength loss and stable, high Q-value performance by forming an alteration portion within the connection portion of the piezoelectric vibrator, preventing surface interference and electrode scattering.

Implementation Method 1

an alteration portion is formed inside the connection portion by irradiating the connection portion with a laser beam

Methodology Applied

Scientific EffectLaser irradiation: Laser

Implementation Method 2

a piezoelectric vibrator using a piezoelectric thin film

Methodology Applied

Scientific EffectPiezoelectric effect: Piezoelectric Effect

Data Source

PatentUS10333490B2Piezoelectric vibrator and frequency adjustment method for piezoelectric vibrator

Publication Date: 2019.06.25 MURATA MFG CO LTD

AI summary

A frequency adjustment method is provided in which a residual substance is unlikely to be generated, the frequency can be adjusted with high precision, and a decrease in strength is made small.A frequency adjustment method for a piezoelectric vibrator includes preparing the piezoelectric vibrator having a base portion, a vibration arm that includes a connection portion connected to the base portion as well as vibration arm main bodies extending from the connection portion and that is made of a single crystal, a lower electrode formed on the vibration arm, a piezoelectric thin film formed on the lower electrode, and an upper electrode formed on the piezoelectric thin film; and forming an alteration portion by irradiating the connection portion with a laser beam.