Crystal Unit Electrode Structure for Low ESR and Stable Vibration
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Solution Overview
Problem
Existing small crystal units face challenges in reducing equivalent series resistor (ESR) values due to increased susceptibility to sub vibrations, requiring precise processing that hinders high productivity and yield in mass production.
Innovation Solution
The electrode structure of the crystal unit features a driven electrode arranged centrally with a two-layer configuration that concentrates and confines vibration energy in the central region, reducing ESR values without precise processing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the crystal blank is made smaller to reduce device size, then the device becomes more compact, but the equivalent series resistor (CI) value increases and sub vibration susceptibility increases
Solution Approach 1:
The patent applies local quality by creating a mesa structure with different heights in different regions of the crystal blank. The central region has a higher mesa structure that concentrates vibration energy, while the peripheral region has a lower structure. This local differentiation allows the small crystal blank to maintain stable vibration characteristics by confining vibration to the central high-mesa region, thereby reducing CI value and sub vibration susceptibility despite the overall small size.
2Reliability
If precise processing is applied to the crystal blank side surface to suppress sub vibration, then vibration stability improves, but manufacturing complexity and production difficulty increase
Solution Approach 1:
The patent segments the crystal blank into distinct regions with different mesa heights - a central high-mesa region and peripheral low-mesa regions. This segmentation is achieved through selective etching that creates the mesa structure in one processing step, avoiding the need for complex multi-step precise processing. The segmented structure naturally confines vibration to the central region while simplifying manufacturing.
Solution Approach 2:
The patent replaces complex mechanical processing (precise side surface machining requiring μm-level control) with a chemical etching process that naturally forms the desired mesa structure. By using etching instead of mechanical machining, the patent achieves the vibration-stabilizing structure with simpler, more controllable chemistry-based processes, reducing manufacturing complexity while maintaining vibration stability.
3Reliability
If precise processing is applied to form desired crystal planes, then sub vibration is suppressed, but productivity decreases due to strict process control requirements
Solution Approach 1:
The patent employs a self-service approach where the etching process automatically forms the mesa structure with appropriate dimensions based on the etching conditions and crystal orientation. The process self-regulates to create the central high-mesa region and peripheral low-mesa regions without requiring complex real-time measurements or adjustments. This self-organizing capability enables mass production while maintaining consistent vibration characteristics.
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 configuration effectively reduces ESR values, improves yield and productivity, and stabilizes oscillation, while suppressing the influence of sub vibrations.
Implementation Method 1
a driven electrode arranged at least at a center on a main surface of a crystal blank, and the driven electrode has a structure for concentrating vibration energy of thickness shear vibration of the crystal blank
Data Source
AI summary
The present invention is able to reduce a CI value without requiring precise processing of a crystal blank.An electrode structure of a crystal unit (1) according to the present invention includes driven electrodes (21, 22) arranged at least at a center on main surfaces (11, 12) of a crystal blank (10). The driven electrodes (21, 22) have a structure in which vibration energy of thickness shear vibration of the crystal blank (10) is concentrated in a central region of the crystal blank (10).