AT-Cut Quartz Crystal Blank Thickness Profile for Lower CI

Solution Overview

Problem

Reducing the crystal impedance (CI) value in quartz crystal resonator units while minimizing the influence of vibration leakage and sub-vibrations, which increase with the reduction in size of the quartz crystal blank.

Innovation Solution

Designing an AT-cut quartz crystal blank with specific thickness and dimension ratios, where the thickness of certain regions decreases with distance from the center, and the long sides are parallel to the Z′ axis, reducing vibration leakage and confining main vibration energy effectively.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Volume of moving object

If the size of the quartz crystal blank is reduced, then the quartz crystal resonator unit size is reduced, but the series resistance increases due to pronounced sub-vibration influence and vibration leakage

Engineering Contradiction:

Improvequartz crystal resonator unit sizeVSAvoidseries resistance

Core Design Contradiction:

Volume of moving objectVSReliability

Solution Approach 1:

The patent applies local quality by creating a thickness gradient in the quartz crystal blank, where the thickness varies from a first thickness at the center to a second thickness at the peripheral portion. This local variation in thickness allows the peripheral portion to suppress vibration leakage while maintaining the overall small size of the resonator unit, thereby reducing series resistance without increasing the overall volume.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The patent introduces a thickness dimension variation within the quartz crystal blank structure. By controlling the thickness to vary from center to periphery, it adds a dimensional parameter that helps suppress vibration leakage and sub-vibrations, thus improving series resistance characteristics while maintaining compact size.

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

2Volume of moving object

If the size of the quartz crystal blank is reduced, then the quartz crystal resonator unit size is reduced, but vibration leakage increases

Engineering Contradiction:

Improvequartz crystal resonator unit sizeVSAvoidvibration leakage

Core Design Contradiction:

Volume of moving objectVSObject-generated harmful factors

Solution Approach 1:

The patent applies local quality by creating a thickness gradient in the quartz crystal blank, where the thickness varies from a first thickness at the center to a second thickness at the peripheral portion. This local variation in thickness allows the peripheral portion to suppress vibration leakage while maintaining the overall small size of the resonator unit, thereby reducing series resistance without increasing the overall volume.

Inventive Principle:

Principle #3Local quality

3Volume of moving object

If the size of the quartz crystal blank is reduced, then the quartz crystal resonator unit size is reduced, but sub-vibration influence increases

Engineering Contradiction:

Improvequartz crystal resonator unit sizeVSAvoidsub-vibration influence

Core Design Contradiction:

Volume of moving objectVSObject-generated harmful factors

Solution Approach 1:

The patent applies local quality by creating a thickness gradient in the quartz crystal blank, where the thickness varies from a first thickness at the center to a second thickness at the peripheral portion. This local variation in thickness allows the peripheral portion to suppress vibration leakage while maintaining the overall small size of the resonator unit, thereby reducing series resistance without increasing the overall volume.

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

The solution effectively reduces the CI value by separating the frequency of the main vibration from sub-vibrations, enhancing the efficiency of vibration energy conversion and output, and minimizing the impact of sub-vibrations on the resonator unit.

Implementation Method 1

an AT-cut quartz crystal blank that is plate-shaped and is rectangular when seen in a direction normal to a main surface

Methodology Applied

Scientific EffectPiezoelectric effect: Piezoelectric Effect

Implementation Method 2

A frequency of a main vibration of the quartz crystal blank is in a range of 49.0 MHz to 52.0 MHz

Methodology Applied

Scientific EffectResonance: Resonance

Data Source

PatentUS10361675B2Quartz crystal blank and quartz crystal resonator unit

Publication Date: 2019.07.23 MURATA MFG CO LTD

AI summary

A rectangular quartz crystal blank having long sides substantially parallel to a Z′ axis of the quartz crystal blank, and short sides substantially parallel to an X axis of the quartz crystal blank. The quartz crystal blank includes a center region, a second region and a third region that are adjacent to the center region along a long-side direction, and a fourth region and a fifth region that are adjacent to the first region along a short-side direction. A thickness of the second region and a thickness of the third region are smaller than a thickness of the first region, and/or a thickness of the fourth region and a thickness of the fifth region are smaller than a thickness of the first region, and 25.90≤W/T≤27.17, where W is a length of a short side and T is a thickness.