Quartz Crystal Blank Thickness Gradient for Low Impedance
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Solution Overview
Problem
Reducing the crystal impedance (CI) value in quartz crystal resonator units while minimizing the size of the quartz crystal blank, which is challenging due to increased series resistance and vibration leakage issues as the size decreases.
Innovation Solution
Designing an AT-cut quartz crystal blank with specific thickness and dimension ratios, where the thickness of certain regions decreases with distance from the center, and the long sides are parallel to the Z' axis, reducing vibration leakage and confining vibration energy effectively.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the size of the quartz crystal blank is reduced, then the resonator unit size is reduced, but the series resistance increases due to pronounced sub-vibration influence and vibration leakage
Solution Approach 1:
The patent applies local quality by creating a thickness gradient in the quartz crystal blank, where the thickness varies from a first thickness at the center to a second thickness at the periphery. This localized thickness variation confines vibration energy to specific regions, reducing vibration leakage at the edges while maintaining the overall small size of the blank, thereby achieving low series resistance in miniaturized resonators
2Volume of moving object
If the size of the quartz crystal blank is reduced, then the resonator unit size is reduced, but vibration leakage increases causing pronounced sub-vibration influence
Solution Approach 1:
By implementing a thickness gradient where the center region has a greater thickness than the peripheral regions, the patent locally modifies the vibration characteristics. This causes vibration energy to be concentrated in the thicker central region, preventing leakage to the thinner edges where sub-vibrations would otherwise be generated, thus eliminating harmful vibration leakage in miniaturized structures
Solution Approach 2:
The patent effectively segments the quartz crystal blank into a central vibration confinement region and peripheral regions, separated by the thickness gradient. This segmentation isolates the main vibration mode in the center while preventing energy transfer to the edges, thereby suppressing sub-vibrations and vibration leakage in small-sized resonators
3Volume of moving object
If the thickness of the quartz crystal blank is reduced, then the resonator unit size is reduced, but the crystal impedance (CI) value increases
Solution Approach 1:
The patent uses local quality by creating a thickness gradient that is thicker at the center and thinner at the periphery. This localized thickness variation increases the effective vibrating mass in the center region, which improves the crystal impedance (CI) value even when the overall blank size is reduced, thereby achieving low CI in miniaturized resonators
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 effectively reduces the CI value by separating the frequency of the main vibration from sub-vibrations, enhancing the conversion of vibration energy into electric signals and minimizing the influence of sub-vibrations, thereby improving the performance of the quartz crystal resonator unit.
Implementation Method 1
AT-cut quartz crystal blank that is plate-shaped and is rectangular when seen in a direction normal to a main surface
Data Source
AI summary
A rectangular quartz crystal blank having long sides substantially parallel to a Z′ axis of the quartz crystal blank, and short sides substantially parallel to an X axis of the quartz crystal blank. The quartz crystal blank includes a first center region, a second region and a third region that are adjacent to the first region along a long-side direction, and a fourth region and a fifth region that are adjacent to the first region along a short-side direction. A thickness of the second region and a thickness of the third region are smaller than the thickness of the first region, and/or a thickness of the fourth region and a thickness of the fifth region are smaller than the thickness of the first region, and 12.26≤W/T≤13.02, where W is a length of a short side and T is a thickness.