AT-Cut Crystal Element Side Surface Geometry for Vibration Reduction
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Solution Overview
Problem
Conventional AT-cut crystal resonators face challenges in achieving improved properties due to limitations in fabrication methods, particularly with mechanical processing, which affects the precision and efficiency of forming crystal elements.
Innovation Solution
The development of an AT-cut crystal element with side surfaces intersecting the Z′-axis, comprising three specific surfaces: an m-surface and two additional surfaces obtained by rotating the principal surface by -74±5° and -56±5°, respectively, along the X-axis, combined with a unique etching process using hydrofluoric acid and strategically displaced etching resist masks to form a beak-shaped structure, reducing unnecessary vibrations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If mechanical processing is used to fabricate crystal elements, then manufacturing precision can be maintained, but productivity decreases and downsizing becomes difficult
Solution Approach 1:
The patent replaces mechanical processing methods with photolithography and wet etching techniques. The crystal elements are formed by depositing electrode patterns through photolithography and removing unwanted material through wet etching, eliminating the need for mechanical machining and enabling high-precision fabrication at smaller scales with higher productivity.
Solution Approach 2:
The patent introduces mask displacement in the Z'-direction (thickness direction) as a new dimensional parameter. By displacing the etching resist mask by a predetermined amount Δz = 0.75×T±20% from the front surface, the etching process creates the desired side surface geometry without mechanical intervention, resolving the contradiction between precision and productivity.
2Ease of manufacture
If conventional etching processes are used, then manufacturing simplicity is maintained, but vibration leakage increases reducing resonator performance
Solution Approach 1:
The patent applies preliminary action by pre-displacing the etching resist mask by a predetermined amount Δz before performing the etching process. This preliminary positioning of the mask determines the final side surface geometry, ensuring that the etching creates the optimal shape for reducing vibration leakage while maintaining process simplicity.
Solution Approach 2:
The patent changes the etching process parameter by introducing mask displacement Δz as a controlled variable. By adjusting the mask position in the Z'-direction by a specific amount (0.75×T±20%), the etching process transforms from a simple planar cut to a precision geometric formation that optimizes vibration characteristics without complicating the manufacturing process.
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 enhances the vibration characteristics of the AT-cut crystal resonator, improving its properties by minimizing unwanted vibrations and achieving better performance compared to conventional designs.
Implementation Method 1
an etching resist mask for forming an outer shape is formed on a quartz substrate, and a part on the quartz substrate without being covered with the mask is dissolved by the wet etching
Implementation Method 2
AT-cut crystal element
Data Source
AI summary
An AT-cut crystal element is provided for reducing unnecessary vibration and for improving impedance of a resonator. Two side surfaces intersecting with a Z′-axis of a crystallographic axis of crystal are constituted of three surfaces of a first surface as an m-surface of quartz crystal, a second surface that intersects with the first surface and is other than the m-surface, and a third surface that intersects with the second surface and is other than the m-surface. Moreover, the second surface is a surface corresponding to a surface obtained by rotating a principal surface of the AT-cut crystal element by −74±3° having an X-axis of crystal as a rotation axis, and the third surface is a surface corresponding to a surface obtained by rotating the principal surface by −56±3° having the X-axis of the crystal as the rotation axis.