Quartz Resonator Structure for High Frequency and Low CI
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Solution Overview
Problem
Existing piezoelectric resonator elements face challenges in achieving high frequencies while maintaining a low CI value, as the CI value tends to increase with higher frequencies, limiting the performance of oscillators.
Innovation Solution
A resonator element design featuring a quartz crystal substrate with a resonator portion and a support portion of increased thickness, along with excitation electrodes, where the area of the excitation electrodes is limited to 35% or less of the resonator portion's area, and the resonator element is housed in a container to stabilize the oscillation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the oscillation frequency is increased to meet high-speed communication demands, then the communication speed and capacity are improved, but the CI value increases which degrades oscillator performance
Solution Approach 1:
The patent applies local quality by creating a thickness difference between the resonator portion and support portion of the quartz crystal substrate. The resonator portion has a smaller thickness than the support portion, which locally optimizes the resonator region to reduce CI value while maintaining overall structural integrity through the thicker support portion. This local differentiation allows high-frequency operation with reduced parasitic capacitance.
Solution Approach 2:
The patent changes the thickness parameter of the quartz crystal substrate to resolve the contradiction. By setting the resonator portion thickness to be smaller than the support portion thickness, the design achieves reduced CI value at high frequencies. This parameter optimization enables oscillation frequencies of 300 MHz or higher while maintaining CI values below 0.5 pF, thus preserving oscillator performance.
2Reliability
If the area of excitation electrodes is reduced to lower CI value, then the parasitic capacitance is reduced, but the excitation efficiency may be compromised
Solution Approach 1:
The patent positions excitation electrodes specifically within the resonator portion rather than distributing them across the entire substrate. This localized electrode placement in the thinner resonator region optimizes the electric field distribution for efficient excitation while minimizing parasitic capacitance to external structures.
Solution Approach 2:
The patent addresses the electrode area issue by transitioning from a two-dimensional area optimization problem to a three-dimensional solution. By reducing the thickness of the resonator portion beneath the electrodes, the patent achieves lower CI value through reduced volume and surface area exposed to external capacitance, while maintaining adequate electrode area for excitation.
3Reliability
If the thickness of the resonator portion is reduced to lower CI value, then the parasitic capacitance is reduced, but the mechanical strength and rigidity may be compromised
Solution Approach 1:
The patent segments the quartz crystal substrate into two distinct functional regions: a thin resonator portion for low CI value and a thick support portion for mechanical strength. This segmentation allows each region to be optimized independently - the resonator portion minimizes parasitic capacitance while the support portion provides structural integrity and mounting capability.
Solution Approach 2:
The patent applies local quality by giving different thicknesses to different portions of the substrate. The resonator portion has reduced thickness optimized for electrical performance, while the support portion maintains greater thickness for mechanical support. This local differentiation resolves the contradiction between electrical and mechanical requirements.
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 design achieves stable production of resonators and oscillators with high frequencies and low CI values, reducing plate thickness variation and turbulence during etching, thereby enhancing rigidity and maintaining performance.
Implementation Method 1
a quartz crystal substrate having a resonator portion and a support portion
Implementation Method 2
a resonator portion including a resonator region, and a support portion having a thickness larger than a thickness of the resonator portion
Data Source
AI summary
A resonator element includes: a quartz crystal substrate having a resonator portion and a support portion having a thickness larger than a thickness of the resonator portion; and an excitation electrode disposed in the resonator portion, in which an oscillation frequency is 300 MHz or more, and an area of the excitation electrode is 35% or less of an area of the resonator portion.