Quartz Resonator Electrode Geometry for Spurious Vibration Suppression
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Solution Overview
Problem
The challenge is to enhance the frequency accuracy and production yield of AT cut quartz crystal resonators while minimizing the frequency jump phenomenon due to spurious vibration coupling, which occurs when reducing the thickness of the vibrating portion for higher frequency applications.
Innovation Solution
A resonator element design featuring excitation electrodes with specific area ratios and shapes, where three corners of a virtual quadrangle are cut out, concentrating main vibration energy and reducing the area of spurious vibration, thereby maintaining frequency stability and reducing capacitance ratio.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the thickness of the vibrating portion is reduced to increase frequency, then the frequency is increased, but the adjustment sensitivity of frequency is increased causing poor final frequency accuracy and lowered production yield
Solution Approach 1:
The patent applies local quality by creating a thick portion at specific locations (corners or peripheral portions) of the vibrating portion while maintaining a thinner central region. This localized thickness variation allows the resonator to achieve higher frequency through reduced overall thickness while the thick portions provide mechanical support and stability, reducing frequency adjustment sensitivity and improving manufacturing precision.
2Speed
If the thickness of the vibrating portion is reduced to increase frequency, then the frequency is increased, but the main vibration couples with spurious vibration causing frequency jump phenomenon and unstable oscillation
Solution Approach 1:
The patent creates localized thick portions at corners or peripheral areas of the vibrating portion. These thick portions act as mechanical anchors that suppress spurious vibration modes while allowing the central thinner region to vibrate at the desired frequency. This local thickness variation decouples the main vibration from spurious vibrations, preventing frequency jumping and ensuring stable oscillation.
3Adaptability or versatility
If four corners of the excitation electrode are cut out to reduce capacitance ratio and increase frequency variable sensitivity, then the capacitance ratio is reduced and frequency variable sensitivity is increased, but the main vibration couples with spurious vibration due to plane parallelism variation causing frequency jump
Solution Approach 1:
Instead of cutting out corners of the excitation electrode, the patent creates thick portions in the substrate at corner or peripheral locations. This approach maintains the full area of the excitation electrode for optimal capacitance coupling while the localized thick portions mechanically suppress spurious vibrations. This resolves the contradiction by achieving frequency variable sensitivity through electrode area optimization without compromising oscillation stability.
Solution Approach 2:
The patent extracts the spurious vibration suppression function from the excitation electrode geometry (corner cutting) and relocates it to the substrate structure (thick portions). This separation allows the excitation electrode to focus on providing optimal electrical coupling and capacitance ratio, while the substrate thick portions handle mechanical vibration control, preventing frequency jump phenomena.
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 design achieves stable main vibration, reduces spurious vibration frequency, and decreases the capacitance ratio, leading to improved frequency accuracy and production yield, with enhanced temperature characteristics and reduced ohmic loss.
Implementation Method 1
a substrate which vibrates in a thickness shear vibration
Implementation Method 2
AT cut quartz crystal resonator that excites thickness shear vibration
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%.