Quartz Vibrating Piece Electrode Layout for Unwanted Mode Suppression
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Solution Overview
Problem
Piezoelectric devices with SC-cut quartz crystal pieces face issues with unwanted responses (A-mode and B-mode) that require additional filtering, increasing complexity and cost, and flexure vibrations lead to energy loss and decreased Q factor, complicating the suppression of these unwanted modes.
Innovation Solution
A piezoelectric vibrating piece with doubly rotated quartz-crystal electrodes, arranged in a specific configuration on the X″Z″-surface, and obliquely disposed excitation electrodes, along with optional bar electrodes, to suppress unwanted modes and flexure vibrations, reducing the need for additional filtering and enhancing vibration efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If parallel electric field excitation is applied to suppress B-mode unwanted response, then the unwanted response is suppressed, but crystal impedance becomes high
Solution Approach 1:
The patent changes the orientation parameter of the excitation electrode from parallel to oblique relative to the Y''-axis, and modifies the electrode shape parameter by adding inclined portions that gradually decrease in thickness. These parameter changes enable suppression of B-mode unwanted response while maintaining low crystal impedance, resolving the technical contradiction.
2Object-generated harmful factors
If excitation electrodes are disposed to suppress unwanted modes, then unwanted responses are reduced, but flexure vibration is generated causing energy loss and decreased Q factor
Solution Approach 1:
The patent optimizes the orientation parameter of the excitation electrode to 260°-300° counterclockwise about the Y''-axis, and designs the electrode shape with inclined portions. These parameter changes suppress unwanted A-mode and B-mode responses while minimizing flexure vibration generation, thereby reducing energy loss and maintaining high Q factor.
3Object-generated harmful factors
If filter or similar part is added to suppress B-mode, then unwanted response is suppressed, but circuit complexity and production cost increase
Solution Approach 1:
The patent extracts the unwanted response suppression function from the external filter component and integrates it into the piezoelectric vibrating piece itself through the obliquely disposed excitation electrode with specific orientation (260°-300° about Y''-axis) and shape design. This eliminates the need for separate filter components, simplifying the circuit and reducing production cost.
4Power
If excitation electrode has predetermined shape or position, then main vibration C-mode is excited, but flexure vibration is generated superimposing on C-mode
Solution Approach 1:
The patent optimizes the position parameter by orienting the excitation electrode at 260°-300° counterclockwise about the Y''-axis, and modifies the shape parameter by incorporating inclined portions that gradually decrease in thickness toward the end portion. These parameter optimizations enable effective excitation of the main C-mode vibration while suppressing the generation of harmful flexure vibrations.
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 configuration effectively suppresses unwanted responses and flexure vibrations, simplifying the circuit, reducing production costs, and improving the Q factor and energy efficiency of the main vibration mode.
Implementation Method 1
A piezoelectric device includes a piezoelectric vibrating piece that vibrates at a predetermined frequency
Data Source
AI summary
A piezoelectric vibrating piece includes a vibrating piece body including a vibrator and at least one pair of excitation electrodes formed on a front surface and a back surface of the vibrator. The vibrating piece body is a twice rotated quartz-crystal vibrating piece. The pair of excitation electrodes are arranged in a Z′″-axis direction determined by an X′″-axis and obliquely disposed with respect to the Y″-axis direction. The X′″-axis is rotated by 260° to 300° counterclockwise about a Y″-axis using a +X″-axis direction as a reference. The pair of excitation electrodes are formed to have respective semicircle shapes including straight line portions extending in the X′″-axis direction and to be disposed in a state where the straight line portions overlapping with one another. The straight line portion of the excitation electrode includes an inclined portion that gradually decreases in thickness toward an end portion of the excitation electrode.