AT-Cut Crystal Sidewall Geometry for Lower Vibration Leakage
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Solution Overview
Problem
The downsizing of AT-cut crystal units has made it challenging to manufacture crystal elements using mechanical processing methods, leading to a need for alternative techniques such as photolithography and wet etching to produce AT-cut crystal elements with specific side surface configurations that minimize vibration leakage and enhance properties.
Innovation Solution
An AT-cut crystal element is designed with two side surfaces intersecting the Z′-axis, each composed of three surfaces, where the surfaces are rotated relative to the crystallographic axes to achieve specific angles and dimensions, optimizing the conversion percentage from thickness twist to surface-shear vibration, thereby reducing vibration leakage and improving unit properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If mechanical processing is used to manufacture crystal elements, then manufacturing precision can be maintained, but it becomes difficult to manufacture as crystal units are downsized
Solution Approach 1:
The patent replaces mechanical processing methods with photolithography and wet etching techniques to manufacture AT-cut crystal elements. This substitution enables precise manufacturing of downsized crystal units while maintaining manufacturing precision, as photolithography allows for accurate pattern transfer and wet etching provides controlled material removal at small scales where mechanical processing becomes inadequate.
2Reliability
If side surfaces are configured with multiple surfaces to reduce vibration leakage, then crystal unit properties are improved, but device complexity increases
Solution Approach 1:
The patent optimizes specific parameters of the side surfaces, including the number of surfaces (three surfaces per Z′-surface), the angles of each surface relative to crystallographic axes (first surface at 4°±3.5°, second surface at -57.5°±3.5°, third surface at -42°±3.5°), and the dimensions (length D and thickness t with ratio M=D/t). By carefully controlling these parameters, the patent achieves reduced vibration leakage and improved crystal unit properties while managing the complexity through standardized geometric configurations.
3Loss of energy
If conversion percentage from thickness twist to surface-shear vibration is reduced, then vibration leakage is minimized, but manufacturing precision requirements increase
Solution Approach 1:
The patent establishes specific parameter ranges for surface angles (4°±3.5°, -57.5°±3.5°, -42°±3.5°) and dimensional ratios (M=D/t) that optimize the conversion percentage from thickness twist to surface-shear vibration. By defining these parameter ranges, the patent achieves reduced vibration leakage (conversion percentage at predetermined value Th or less) while providing manufacturing guidance that balances precision requirements with practical manufacturability through photolithography and wet etching processes.
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 optimized AT-cut crystal element with specific surface configurations achieves reduced vibration leakage and enhanced properties, as evidenced by lower impedance values and improved frequency stability, allowing for more precise control over crystal unit design and performance.
Implementation Method 1
AT-cut crystal element - refers to a crystal element using a cut which is AT-cut with respect to a crystallographic axis of a crystal
Data Source
AI summary
An AT-cut crystal element includes a crystal element having two side surfaces (namely, a Z′-surface) intersecting with a Z-axis of a crystallographic axis thereof. At least one of the two side surfaces is constituted of three of first to third surfaces. The first to the third surfaces meeting following conditions: the first to the third surfaces intersect with one another in this order and formed by rotating a principal surface of the crystal element by predetermined angles; and expressing the angle of the first surface as θ1, a length of the first surface as D, a thickness of a part of the crystal element having the principal surface as t, and M=D/t, and a conversion percentage as fn (M, (θ1)), the θ1 and the M are set such that the conversion percentage fn (M, (θ1)) becomes a predetermined value Th or less.