Thickness-Shear Crystal Unit Electrode Ratio for Stable Frequency
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Solution Overview
Problem
Existing crystal units, particularly those vibrating in a thickness-shear mode, face challenges in maintaining stable frequency characteristics when drive power changes, which affects their drive level characteristics.
Innovation Solution
A crystal unit design with excitation electrodes on both front and back surfaces of the crystal element, where the ratio of the total excitation electrode thickness to the crystal element thickness (t/T) is maintained between 0.026 to 0.030, enhancing the drive level characteristics by minimizing frequency fluctuations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the excitation electrode thickness is increased to improve adhesion and drive level characteristics, then the frequency stability improves, but the manufacturing precision becomes more difficult to control
Solution Approach 1:
The patent applies parameter changes by precisely controlling the excitation electrode thickness ratio (t/T) within the range of 0.026 to 0.030. This specific parameter range optimizes both the drive level characteristics and frequency stability, resolving the contradiction between reliability and manufacturing precision.
2Ease of manufacture
If the excitation electrode structure is simplified to ease manufacturing, then the manufacturing cost decreases, but the frequency stability deteriorates
Solution Approach 1:
The patent maintains a controlled electrode thickness ratio (t/T) of 0.026 to 0.030, which balances manufacturing simplicity with frequency stability requirements, allowing cost-effective production while maintaining reliable performance.
3Strength
If the crystal element thickness is increased to improve mechanical strength, then the structural integrity improves, but the drive level characteristics worsen
Solution Approach 1:
The patent optimizes the ratio of excitation electrode thickness to crystal element thickness (t/T) within 0.026 to 0.030, which allows the crystal element to maintain adequate thickness for structural integrity while ensuring excellent drive level characteristics through proper electrode sizing.
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 proposed design achieves a frequency change rate within ±6 ppm to ±4 ppm, ensuring stable frequency operation and improved drive level characteristics, independent of crystal element size or excitation electrode size variations.
Implementation Method 1
a crystal element that vibrates in a thickness-shear mode
Implementation Method 2
excitation electrodes that are disposed on front and back surfaces of the crystal element
Data Source
AI summary
A crystal unit includes a crystal element, excitation electrodes, and a container. The crystal element vibrates in a thickness-shear mode. The excitation electrodes are disposed on front and back surfaces of the crystal element. The crystal element is mounted to the container. The excitation electrodes are disposed on the crystal element. When a thickness of the crystal element is expressed as T, and a total thickness of the excitation electrodes disposed on the front and back surfaces of the crystal element is expressed as t, a ratio t/T is from 0.026 to 0.030.