AT-Cut Quartz Resonator Electrodes for Stable Thickness Shear Vibration
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Solution Overview
Problem
The challenge is to enhance the frequency accuracy and stability of AT cut quartz crystal resonators while minimizing the thickness of the vibrating portion, as reducing thickness increases frequency adjustment sensitivity, leading to poor frequency accuracy and lower production yield, and introduces instability due to spurious vibration coupling.
Innovation Solution
A resonator element design with excitation electrodes shaped as virtual quadrangles, where three corners are cut out, concentrating main vibration energy and reducing spurious vibration area, thereby maintaining frequency stability and reducing capacitance ratio, while allowing efficient energy trapping and minimizing ohmic loss.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the thickness of the vibrating portion is reduced to increase frequency, then the frequency increases, but the adjustment sensitivity increases leading to poor frequency accuracy
Solution Approach 1:
The patent applies local quality by creating a non-uniform electrode area distribution - the central electrode area is larger while peripheral areas are reduced. This local variation in electrode geometry allows the central region to maintain strong main vibration excitation while peripheral regions contribute less to spurious vibrations, thereby maintaining frequency accuracy even at higher frequencies achieved through reduced thickness.
2Speed
If the thickness of the vibrating portion is reduced to increase frequency, then the frequency increases, but the production yield decreases
Solution Approach 1:
By implementing local quality through non-uniform electrode area distribution, the patent reduces sensitivity to manufacturing variations in the thickness direction. The larger central electrode area provides robust main vibration excitation that is less affected by thickness variations, while the reduced peripheral areas minimize spurious vibration coupling. This design tolerance to manufacturing variations directly improves production yield at higher frequencies.
3Quantity of substance
If the area of excitation electrode is reduced to reduce capacitance ratio, then the capacitance ratio decreases and frequency variable sensitivity increases, but the main vibration may couple with spurious vibration
Solution Approach 1:
The patent resolves this contradiction by applying local quality - the central electrode region maintains larger area to strongly excite main vibration and provide stability, while peripheral electrode regions have reduced area to minimize spurious vibration coupling. This spatially differentiated electrode design allows the overall electrode area to be effectively reduced for lower capacitance ratio, while local central area preservation maintains oscillation stability.
Solution Approach 2:
The electrode area is segmented into functionally different regions - a central region with larger area for main vibration excitation and peripheral regions with smaller areas. This segmentation allows different parts of the electrode to serve different functions: the central portion ensures stable main vibration while the reduced peripheral portions minimize spurious vibration coupling, achieving both low capacitance ratio and high stability.
4Reliability
If the excitation electrode shape is modified to reduce spurious vibration, then oscillation stability improves, but the electrode geometry becomes more complex
Solution Approach 1:
The patent implements local quality by creating a electrode geometry with a larger central area and reduced peripheral areas. This localized geometric modification targets specifically the peripheral regions where spurious vibrations originate, while preserving the central region for main vibration excitation. The resulting geometry is moderately complex but achieves significant improvement in oscillation stability by suppressing spurious vibration coupling.
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 achieves stable thickness shear vibration with reduced frequency variation, improved frequency accuracy, and increased production yield by concentrating main vibration energy and minimizing spurious vibration, resulting in a resonator with enhanced frequency-temperature characteristics and reduced frequency jump phenomena.
Implementation Method 1
a resonator element including a substrate that vibrates in a thickness shear vibration... a first excitation electrode that is provided on the first main surface; and a second excitation electrode that is provided on the second main surface
Data Source
AI summary
A resonator element includes a substrate that vibrates in a thickness shear vibration, a first excitation electrode that is provided on one main surface of the substrate and has a shape in which at least three corners of a virtual quadrangle are cut out, and a second excitation electrode that is provided on the other main surface of the substrate, and a ratio (S2/S1) of an area S1 of the virtual quadrangle and an area S2 of the first excitation electrode satisfies a relationship of 69.2%≦(S2/S1)≦80.1%.