Resonator Mesa Structure for Low Crystal Impedance
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Solution Overview
Problem
Existing piezoelectric resonator elements face challenges in miniaturization and reducing crystal impedance (CI) values while maintaining optimal vibration characteristics, as they are prone to etching corrosion and unnecessary mode binding, which affects their performance.
Innovation Solution
A resonator element with a mesa structure substrate, specifically a rotated Y-cut quartz crystal substrate, is designed with a two-stage type mesa structure and optimized etching parameters, where the distance between the vibration section and bonding region, and the etching amount ratio, are carefully controlled to minimize CI values and prevent etching corrosion, allowing for miniaturization while maintaining improved vibration characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the resonator element is miniaturized, then the size is reduced, but the CI value increases
Solution Approach 1:
The substrate is divided into distinct functional regions: a vibration section with a first thickness for piezoelectric vibration, and a bonding region with a second thickness for mounting. This segmentation allows the vibration section to be miniaturized while the bonding region provides sufficient area for reliable bonding, thus reducing overall size while maintaining low CI values through optimized vibration confinement.
Solution Approach 2:
Different regions of the substrate are given different thicknesses to optimize local functions. The vibration section has a first thickness optimized for vibration characteristics and low CI, while the bonding region has a second thickness optimized for bonding strength. This local differentiation enables miniaturization of the vibration section without compromising bonding reliability.
2Reliability
If the etching amount is increased to reduce CI value, then the CI value decreases, but etching corrosion occurs
Solution Approach 1:
The patent optimizes the etching amount to a specific range (5-20 μm) that achieves the desired CI value reduction while avoiding etching corrosion. This parameter optimization balances the competing requirements of lowering CI through increased etching while preventing the harmful effects of excessive etching such as corrosion and structural damage.
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 decreases CI values while preventing etching corrosion and deteriorated vibration characteristics, enabling miniaturization of resonator elements with enhanced performance and reduced manufacturing costs.
Implementation Method 1
a piezoelectric resonator element tends to be small
Implementation Method 2
a vibration section that vibrates in a thickness shear vibration mode
Data Source
AI summary
When a length along a vibrating direction of the thickness shear vibration of a multi-stage type mesa substrate of A resonator element is x, a thickness of the vibration section is t, and a distance between the vibration section and the bonding region is y, y is in a range of −0.0151×(x/t)+0.3471≦y≦−0.0121×(x/t)+0.3471.