Piezoelectric Resonator Thick-Walled Mesa Structure
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Solution Overview
Problem
AT-cut quartz crystal resonators face challenges in increasing output frequency while maintaining rigidity and impact resistance, as thinner vibrating portions lead to decreased rigidity and generation of etching residues that reduce the effective vibrating area and CI value ratios.
Innovation Solution
The design incorporates thick-walled portions protruding beyond the principal surfaces of the vibrating portion, forming a mesa structure to increase the effective area and support the vibrating portion, with slits in the thick-walled portions to mitigate stress and improve frequency-temperature characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the vibrating portion is made thinner to increase output frequency, then the output frequency increases, but the rigidity of the vibrating portion decreases and impact resistance deteriorates
Solution Approach 1:
The resonator structure is segmented into distinct regions: a thin vibrating portion for high-frequency operation and separate thick-walled portions (first, second, and third thick-walled portions) for structural support. This segmentation allows each region to optimize for its specific function without compromising the other.
Solution Approach 2:
Different thickness characteristics are applied to different locations: the vibrating portion has small thickness for high frequency, while the thick-walled portions have large thickness for rigidity and impact resistance. This local differentiation resolves the contradiction by allowing each region to have the thickness appropriate for its function.
2Shape
If etching is used to form the inverted mesa structure, then the vibrating portion and thick-walled portions are formed, but etching residues are generated at the boundaries reducing the effective vibrating area and CI value ratios
Solution Approach 1:
The harmful etching residues are extracted or removed through additional etching steps that specifically target the boundary regions. The patent employs multiple etching processes to eliminate residues at the interfaces between the vibrating portion and thick-walled portions, ensuring clean boundaries and accurate dimensional control.
Solution Approach 2:
The patent performs preliminary etching to form the basic inverted mesa structure, then follows with additional etching steps to remove residues before final processing. This sequential approach ensures that residues are eliminated before they can affect the final vibrating characteristics and CI value ratios.
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 configuration enhances the resonator's frequency stability, impact resistance, and CI value ratios, achieving higher frequency output while maintaining structural integrity and reducing stress-related frequency variations.
Implementation Method 1
An AT-cut quartz crystal resonator which is an example of a resonator is used in various fields such as in a piezoelectric oscillator and an electronic apparatus since it excites a thickness-shear vibration mode as its main vibration mode
Implementation Method 2
AT-cut quartz crystal resonator
Data Source
AI summary
A piezoelectric resonating element includes a piezoelectric substrate having a rectangular vibrating portion and a thick-walled portion, excitation electrodes and, and lead electrodes. The thick-walled portion includes a fourth thick-walled portion, a third thick-walled portion, a first thick-walled portion, and a second thick-walled portion. The third thick-walled portion includes a third slope portion and a third thick-walled body, and at least one slit is formed in the third thick-walled portion.