Stepped-Thickness Crystal Element for High-Frequency Stability
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Solution Overview
Problem
The mechanical strength of crystal plates used in high-frequency crystal elements is compromised due to their thinness, leading to distortion and deterioration in electrical characteristics, particularly at oscillation frequencies of 150 MHz and above.
Innovation Solution
The crystal element is designed with a vibration part, a thicker flat plate part, and an even thicker fixing part, where the flat plate part supports the outer edge of the thin vibration part, and the fixing part supports the outer edge of the flat plate part, maintaining mechanical strength and stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the crystal plate is made thinner to achieve higher oscillation frequency, then the oscillation frequency is improved, but the mechanical strength deteriorates
Solution Approach 1:
The crystal plate is segmented into three distinct parts with different thicknesses: a thin vibration part (11) for high-frequency oscillation, a medium-thickness flat plate part (12) for support, and a thick fixing part (13) for mechanical strength. This segmentation allows each part to optimize its function without compromising the others.
Solution Approach 2:
Different parts of the crystal plate are given different local qualities (thicknesses) suited to their specific functions. The vibration part is locally thin for high frequency, while the fixing part is locally thick for mechanical strength, resolving the contradiction between frequency and strength.
2Speed
If the crystal plate is made thinner to achieve higher oscillation frequency, then the oscillation frequency is improved, but distortion occurs
Solution Approach 1:
By segmenting the crystal plate into vibration part, flat plate part, and fixing part with progressively increasing thickness, the structure provides stable support zones that prevent distortion of the thin vibration region while maintaining high oscillation frequency capability.
Solution Approach 2:
The thicker flat plate part and fixing part act as pre-positioned support structures that cushion and prevent distortion before it can affect the thin vibration part, ensuring stable operation at high frequencies.
3Speed
If the crystal plate is made thinner to achieve higher oscillation frequency, then the oscillation frequency is improved, but the electrical characteristics deteriorate
Solution Approach 1:
The segmentation into three thickness zones ensures that the thin vibration part achieves high frequency while the thicker supporting parts maintain structural integrity, thereby preserving electrical characteristics despite the thinness of the vibration region.
Solution Approach 2:
By providing locally different thickness qualities in different regions, the invention maintains the electrical characteristics reliability through adequate support structure thickness while allowing the vibration region to be thin for high frequency operation.
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 maintains the mechanical strength of the crystal element even as the vibration part becomes thinner with increasing oscillation frequency, ensuring stable electrical characteristics and reducing the likelihood of distortion.
Implementation Method 1
The crystal element of the thickness-shear vibration mode is acquired by forming excitation electrodes made of a metal film pattern on both main surfaces of an AT-cut crystal plate
Implementation Method 2
The crystal device generates a specific oscillation frequency by using the piezoelectric effect and the inverse piezoelectric effect of the crystal element
Data Source
AI summary
The crystal element includes: a vibration part including a first face and a second face; a flat plate part including a first face and a second face, which has a thickness thicker than a thickness of the vibration part and is disposed in an outer edge of the vibration part on a plan view; a fixing part including a first face and a second face, which has a thickness thicker than the thickness of the flat plate part and is disposed in an outer edge of the flat plate part on a plan view; an excitation electrode disposed on the first face and the second face of the vibration part; a mounting electrode disposed at least on one of the first face and the second face of the fixing part; and a wiring electrode that electrically connects the excitation electrode and the mounting electrode.