Crystal Oscillator Electrode Structure for Spurious Oscillation Reduction
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Solution Overview
Problem
Conventional crystal oscillators with thickness-shear vibrations face challenges in reducing spurious oscillations, which affect their performance as reference signal sources and band-pass filters.
Innovation Solution
A crystal oscillation element with a crystal piece and an excitation electrode unit, where the electrode unit has flat plate portions and thick film portions with protruding portions that extend along the principal planes, enhancing the electromechanical coupling constant and reducing spurious oscillations by concentrating strain on the protruding portions during thickness-shear vibrations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If the mesa thickness ratio of the inverted mesa shape of the excitation electrode is changed to flatten the vibration displacement shape, then spurious oscillations are reduced, but further reduction of spurious oscillations is still desired
Solution Approach 1:
The excitation electrode is divided into multiple functional regions: a flat plate portion and a thick film portion with protruding portions. This segmentation allows different parts of the electrode to serve different purposes - the flat plate portion provides a base structure while the thick film portion with protrusions specifically targets spurious oscillation reduction by concentrating strain at discrete locations.
Solution Approach 2:
The thick film portion is strategically positioned at specific locations on the excitation electrode, and the protruding portions create localized areas of concentrated strain. This local quality enhancement targets specific problem areas (spurious oscillations) without requiring changes to the entire electrode structure, thereby reducing overall complexity while achieving the desired effect.
2Reliability
If the excitation electrode has thick film portions with protruding portions to concentrate strain, then the electromechanical coupling constant is enhanced, but the electrode manufacturing complexity increases
Solution Approach 1:
The invention changes the geometric parameters of the excitation electrode by creating protruding portions with specific dimensions. The protruding portions have a defined height (e.g., 0.5-2.0 μm) and width (e.g., 10-50 μm) that can be controlled during fabrication. By optimizing these parameters, the electromechanical coupling constant is enhanced while maintaining manufacturability through standard semiconductor fabrication techniques.
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 effectively increases the electromechanical coupling constant, leading to reduced spurious oscillations and improved vibration characteristics, enhancing the crystal oscillator's performance as a reference signal source and band-pass filter.
Implementation Method 1
when a voltage is applied to the excitation electrode unit, the crystal piece performs thickness-shear vibrations
Implementation Method 2
the thick film portion has first protruding portions that are located at the ends in the axis direction of the first base axis on the principal plane, extend in the axis direction of the second base axis and protrude from the flat plate portion
Data Source
AI summary
A crystal oscillation element includes a crystal piece having principal planes defined by a first base axis and a second base axis that intersects the first base axis, and an excitation electrode unit at the principal planes of the crystal piece. The excitation electrode unit has flat plate portions and thick film portions located at electrode ends on the principal planes and that have a thickness larger than that of the flat plate portions. The thick film portion has first protruding portions at the ends in the axis direction of the first base axis, extend in the axis direction of the second base axis and protrude from the flat plate portion, and second protruding portions at the ends in the axis direction of the second base axis, extend in the axis direction of the first base axis and protrude from the flat plate portion.