Crystal Vibration Element Two-Step Mesa Structure
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Solution Overview
Problem
Existing crystal vibration elements face challenges in achieving improved vibration characteristics and energy trapping effects, particularly in small-sized devices, due to limitations in mesa shape and excitation electrode positioning, which affect the efficiency of thickness shear vibration.
Innovation Solution
A crystal vibration element with a plate-shaped crystal blank featuring a two-step mesa structure and strategically positioned excitation electrodes, where the first mesa parts are positioned inward from the outer edge of the major surface and the second mesa parts have widths equivalent to the first mesa parts, enhancing energy trapping and reducing spurious emissions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the crystal blank is made small-sized, then the device size is reduced, but the vibration characteristics and energy trapping effects deteriorate
Solution Approach 1:
The crystal blank is divided into multiple functional regions through the two-step mesa structure: a first mesa part for primary vibration and a second mesa part for energy trapping. This segmentation allows the small-sized device to maintain good vibration characteristics by separating the vibration generation function from the energy confinement function, resolving the contradiction between miniaturization and vibration performance.
Solution Approach 2:
Different regions of the crystal blank are given different structural qualities through the two-step mesa design. The first mesa part has a specific height for optimal vibration, while the second mesa part has a different height configuration for energy trapping. This local differentiation of structural properties enables the small-sized device to achieve both good vibration characteristics and effective energy trapping simultaneously.
2Use of energy by moving object
If the excitation electrode is positioned to maximize coverage, then the vibration efficiency is improved, but spurious emissions increase
Solution Approach 1:
The excitation electrode is positioned with specific local quality considerations: it is arranged to overlap with the first mesa part for efficient vibration excitation, while maintaining a controlled distance from the second mesa part to minimize spurious emissions. This selective positioning optimizes the balance between vibration efficiency and spurious emission reduction.
Solution Approach 2:
The two-step mesa structure acts as an intermediary between the excitation electrode and the crystal blank body. The first mesa part serves as the primary interaction zone for efficient energy transfer, while the second mesa part functions as an intermediary barrier that confines energy and reduces spurious emissions, thus mediating between electrode coverage and emission control.
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 improves vibration characteristics and energy trapping, while minimizing spurious emissions, particularly in small-sized devices, by optimizing the distribution of vibration energy and reducing unwanted vibrations.
Implementation Method 1
a plate-shaped crystal blank cut for thickness shear vibration in which a long direction is a vibration direction
Data Source
AI summary
A crystal blank includes a pair of tableland-shaped first mesa parts projecting from a flat plate and a pair of tableland-shaped second mesa parts projecting from the pair of first mesa parts. The flat plate's length in a long direction is less than 1000 μm. The first mesa part is on an inner side of the flat plate's major surface. The second mesa part is on the first mesa part's inner side of an upper surface's outer edge at two ends of the long direction and has a width equivalent to the first mesa part's upper surface at two sides of a short direction. An excitation electrode reaches the second mesa part's outer edge of the upper surface, is located on the inner side of the first mesa part, and on the second mesa part's inner side of the upper surface's outer edge at two sides of the short direction.