Quartz Crystal Resonator Structure With Thinned Coupling Portions

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Solution Overview

Problem

Conventional quartz crystal resonators face challenges in reducing size while maintaining vibration characteristics due to anisotropic etching of quartz crystals, leading to increased outer size and decreased vibration area.

Innovation Solution

A quartz crystal resonator design featuring a body portion with specific excitation electrodes and coupling members made of quartz crystal, where the coupling members have thinner sections than the body portion, allowing for reduced size without compromising vibration confinement.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Volume of moving object

If the size of the piezoelectric chip is reduced, then the outer size decreases, but the area of the vibration portion decreases and vibration characteristics deteriorate

Engineering Contradiction:

Improveouter size of piezoelectric chipVSAvoidvibration characteristics

Core Design Contradiction:

Volume of moving objectVSReliability

Solution Approach 1:

The patent applies local quality by making the coupling portions thinner only at specific locations (where they connect the vibration portion to the frame) while maintaining the full thickness of the vibration portion itself. This localized thinning allows the vibration portion to maintain its full area for good vibration characteristics, while the coupling portions are reduced in size to minimize their impact on vibration. The thinner coupling portions are positioned away from the center of the vibration portion, creating a gradient in thickness that optimizes both size reduction and vibration performance.

Inventive Principle:

Principle #3Local quality

2Reliability

If providing an appropriate area to the vibration portion is prioritized, then vibration characteristics are maintained, but the outer size of the piezoelectric chip increases

Engineering Contradiction:

Improvevibration characteristicsVSAvoidouter size of piezoelectric chip

Core Design Contradiction:

ReliabilityVSVolume of moving object

Solution Approach 1:

The patent segments the piezoelectric chip into distinct functional regions: a vibration portion with full thickness for maintaining vibration characteristics, and thinner coupling portions for size reduction. By dividing the structure into these segments with different thicknesses, the invention allows the vibration portion to maintain its appropriate area while the overall outer size is reduced through the thinner coupling portions that connect to the frame.

Inventive Principle:

Principle #1Segmentation

3Ease of manufacture

If through portions are formed between the frame and vibration portion periphery, then coupling is achieved, but the distance between vibration portion and frame must be comparatively large

Engineering Contradiction:

Improveformation of through portionVSAvoiddistance between vibration portion and frame

Core Design Contradiction:

Ease of manufactureVSVolume of moving object

Solution Approach 1:

Instead of forming through portions that require large distances, the patent inverts the approach by using thinner coupling portions that extend from the vibration portion to the frame. This inversion allows coupling to be achieved with a smaller distance between the vibration portion and frame, as the coupling portions are reduced in thickness rather than requiring large spacing to accommodate through portions.

Inventive Principle:

Principle #13The other way round (Inversion)

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 enables a compact quartz crystal resonator with preserved vibration characteristics, improved coupling strength, and reduced likelihood of extension electrode breakage, while maintaining effective electrical connectivity.

Implementation Method 1

a quartz crystal substrate is wet etched

Methodology Applied

Scientific EffectWet etching:

Implementation Method 2

Because a quartz crystal has an anisotropic crystal structure, the dissolution rate of wet etching differs in accordance with crystal orientation

Methodology Applied

Scientific EffectAnisotropic crystal structure: Anisotropy

Implementation Method 3

piezoelectric devices having a structure in which a piezoelectric chip is interposed between a lid and a base

Methodology Applied

Scientific EffectPiezoelectric effect: Piezoelectric Effect

Data Source

PatentUS11108377B2Quartz crystal resonator and quartz crystal resonator unit

Publication Date: 2021.08.31 MURATA MFG CO LTD

AI summary

A quartz crystal resonator is provided that includes a body portion with first and second main surfaces facing each other and, in plan view has a pair of long sides extending in a first direction and a pair of short sides extending in a second intersecting direction. Moreover, first and second excitation electrodes are disposed on the first and second main surfaces respectively; a frame surrounds the body portion at both ends and is separated from the both ends; and first and second coupling portions extend from the short sides in the first direction with widths of the short sides. At least one of the first and second coupling portions has a portion whose thickness in a third direction is smaller than a thickness in the third direction of a region of the body portion where the first excitation electrode and the second excitation electrode face each other.