Piezoelectric Resonator Electrode Hole Layout for Inharmonic Mode Separation

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Solution Overview

Problem

When the thickness of the quartz crystal element is reduced to increase frequency, it becomes challenging to sufficiently separate the vibration frequency of inharmonic modes from the fundamental wave vibration of the main mode, leading to significant interference.

Innovation Solution

The piezoelectric resonator is designed with a specific relationship between the dimension of the excitation electrode along one direction and the thickness of the quartz crystal element, and a central hole is introduced in the excitation electrode to enhance the electromechanical coupling coefficient.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Speed

If the thickness of the quartz crystal element is reduced to increase frequency, then the operating frequency increases, but the vibration frequency of inharmonic modes cannot be sufficiently separated from the fundamental wave vibration

Engineering Contradiction:

ImprovefrequencyVSAvoidfrequency separation

Core Design Contradiction:

SpeedVSReliability

Solution Approach 1:

The patent applies local quality by creating a hole portion in the central region of the excitation electrode, specifically positioning it where inharmonic mode vibrations occur. This local modification changes the mass distribution and stiffness characteristics at the critical region, enabling frequency separation of inharmonic modes while maintaining the overall electrode function for fundamental mode excitation.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The patent changes geometric parameters of the excitation electrode by introducing a hole portion with specific dimensions and positioning. The hole's size, shape, and location are optimized to alter the vibrational characteristics, specifically increasing the frequency separation between inharmonic modes and the fundamental mode, thereby resolving the frequency separation problem.

Inventive Principle:

Principle #35Parameter changes

2Reliability

If a hole portion is added to the excitation electrode to separate inharmonic mode frequency, then frequency separation improves, but the device complexity increases

Engineering Contradiction:

Improvefrequency separationVSAvoidelectrode structure

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent applies the porous materials principle by introducing a hole portion in the excitation electrode, creating a porous or perforated structure. This modification achieves frequency separation of inharmonic modes while maintaining structural integrity and electrical functionality, balancing performance improvement with manageable structural complexity.

Inventive Principle:

Principle #31Porous materials

3Reliability

If the electromechanical coupling coefficient is improved by design modifications, then the resonator performance enhances, but the manufacturing precision requirements increase

Engineering Contradiction:

Improveelectromechanical coupling coefficientVSAvoidhole portion dimensions

Core Design Contradiction:

ReliabilityVSManufacturing precision

Solution Approach 1:

The patent optimizes the geometric parameters of the hole portion (size, shape, position) to achieve improved electromechanical coupling coefficient and frequency separation. By carefully selecting parameter ranges and relationships, the design balances performance enhancement with manufacturability, ensuring that precision requirements remain within practical manufacturing capabilities.

Inventive Principle:

Principle #35Parameter changes

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 design effectively improves the electromechanical coupling coefficient, reducing the influence of inharmonic modes on the main mode and enhancing the resonator's performance.

Implementation Method 1

a piezoelectric element having a main surface that extends in a first direction and a second direction that intersects with the first direction and having a thickness in a third direction that intersects with the first direction and the second direction

Methodology Applied

Scientific EffectPiezoelectric effect: Piezoelectric Effect

Implementation Method 2

an excitation electrode provided on the main surface, in which, when a dimension of the excitation electrode along the first direction is defined as Le1 and a dimension of the piezoelectric element along the third direction is defined as Tq, a relationship of 45≤Le1/Tq≤120 is established

Methodology Applied

Scientific EffectElectromechanical coupling: Piezoelectric Effect

Implementation Method 3

a first hole portion that penetrates the excitation electrode along the third direction is formed in a central portion of the excitation electrode in the first direction

Methodology Applied

Scientific EffectVibration frequency separation: Resonance

Data Source

PatentUS20250293665A1Piezoelectric resonator, piezoelectric resonator unit, and piezoelectric oscillator

Publication Date: 2025.09.18 MURATA MFG CO LTD

AI summary

A piezoelectric resonator that includes: a piezoelectric element having a main surface that extends in a first direction and a second direction that intersects with the first direction and having a thickness in a third direction that intersects with the first direction and the second direction; and an excitation electrode on the main surface, the excitation electrode including a first hole portion that penetrates the excitation electrode along the third direction in a central portion of the excitation electrode in the first direction, wherein, when a dimension of the excitation electrode along the first direction is defined as (Le1) and a dimension of the piezoelectric element along the third direction is defined as (Tq), 45≤Le1/Tq≤120.