Piezoelectric Resonator Layout for Stable Frequency in Compact Designs
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Solution Overview
Problem
Resonators in electronic devices face challenges in maintaining resonant frequency stability due to Coulomb forces caused by charged insulators or conductors, which can lead to variations in vibration characteristics and size constraints, particularly when reducing the dimensions of the resonator to minimize these effects.
Innovation Solution
A resonator design featuring at least three vibrating arms with a piezoelectric film and electrodes, where the tips of the arms are spaced further from a holding frame, allowing for increased size while minimizing the impact of Coulomb forces and maintaining resonant frequency stability, by setting a larger release width between the tips and the frame, and using mass-loaded tips to enhance vibration characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the gap around the periphery of the vibrating arm is increased to reduce the effect of Coulomb force, then the resonant frequency stability is improved, but the dimensions of the resonator will increase
Solution Approach 1:
The patent introduces a holding arm structure that extends in a direction perpendicular to the vibrating arm, creating a three-dimensional release width configuration. This allows the gap to be optimized in multiple spatial dimensions rather than simply increasing the overall resonator size in one direction.
Solution Approach 2:
The holding arm acts as an intermediary structure between the vibrating arm and the frame, providing a controlled release width that mediates between the need for small resonator size and the need to reduce Coulomb force effects. The holding arm's specific dimensions and positioning create an optimal balance point.
2Volume of moving object
If the dimensions of the base or vibrating arm are reduced to increase the gap size, then the resonator size is reduced, but the vibration characteristics are degraded
Solution Approach 1:
The patent applies different dimensional constraints to different parts of the resonator structure. The base and vibrating arm dimensions are optimized for vibration characteristics, while the holding arm provides a localized increase in release width to reduce Coulomb force effects without compromising the overall vibration performance.
Solution Approach 2:
The resonator is segmented into distinct functional components: the vibrating arm for vibration generation, the base for structural support, and the holding arm for positioning and release width control. This segmentation allows each component to be independently optimized for its specific function.
3Reliability
If the area of the conductive film is increased to release charge, then the Coulomb force effect is reduced, but the device complexity increases
Solution Approach 1:
The patent extracts the charge release function from the conductive film area and relocates it to the holding arm structure through geometric design. By creating sufficient release width in the holding arm, the need for extensive conductive film areas is eliminated, simplifying the overall device structure.
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 allows for a reduced resonator size while suppressing variations in resonant frequency and maintaining stable vibration characteristics, thereby addressing the degradation of driving voltage dependence and parasitic capacitance issues.
Implementation Method 1
a piezoelectric film provided between the first electrode and the second electrode
Implementation Method 2
when an insulator or conductor provided on a surface or between layers becomes charged due to ion beam sputtering or the pyroelectric effect, an attractive or repulsive force may act on the resonator due to the Coulomb force
Implementation Method 3
when an insulator or conductor provided on a surface or between layers becomes charged due to ion beam sputtering
Implementation Method 4
when an insulator or conductor provided on a surface or between layers becomes charged due to ion beam sputtering or the pyroelectric effect
Data Source
AI summary
A resonator is provided that includes a base; at least three vibrating arms that include a piezoelectric film, an upper electrode, and a lower electrode; a frame; and a holding arm. Each vibrating arm includes an arm portion and a tip portion. The holding arm includes a holding side arm that extends parallel to the outer vibrating arm. A release width between the tip portion of the outer vibrating arm and the frame is larger than a release width between the holding side arm and the frame or a release width between the arm portion of the outer vibrating arm and the holding side arm.