Piezoelectric Resonator Electrode Layout for Coupling Stability
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The electromechanical coupling coefficient in quartz crystal resonators deteriorates due to positional deviations in the film thickness portion during manufacturing.
Innovation Solution
A piezoelectric vibration element is designed with a piezoelectric substrate and excitation electrodes, where a mass-adding film is strategically placed to overlap with the electrodes, creating specific acoustic velocity regions that mitigate the effects of positional deviations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a film thickness portion is added to the electrode end portion, then the electromechanical coupling coefficient is improved, but positional deviation during manufacturing causes deterioration in the electromechanical coupling coefficient
Solution Approach 1:
The patent applies local quality by creating different acoustic velocity regions at different locations on the piezoelectric substrate. Specifically, a first low acoustic velocity region is formed at the electrode end portion where the mass-adding film is provided, while a second low acoustic velocity region is formed at a position different from the electrode end portion. This localized variation in acoustic velocity properties allows the structure to compensate for positional deviations in the mass-adding film, thereby maintaining stable electromechanical coupling coefficient despite manufacturing variations.
2Reliability
If a mass-adding film is provided to create low acoustic velocity regions, then the electromechanical coupling coefficient is improved, but the device complexity increases
Solution Approach 1:
The patent segments the acoustic velocity characteristics into distinct regions: a first low acoustic velocity region at the electrode end portion and a second low acoustic velocity region at a different position. This segmentation is achieved by strategically placing mass-adding films in specific locations rather than uniformly across the substrate. The segmented approach allows independent optimization of different regions, improving electromechanical coupling while keeping the overall structure manageable through localized modifications rather than global complexity.
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 proposed design effectively suppresses the deterioration of the electromechanical coupling coefficient, maintaining its stability even with manufacturing variations.
Implementation Method 1
a second region where the piezoelectric substrate, the first excitation electrode, and the second excitation electrode overlap with the first part of the mass-adding film is defined as a first low acoustic velocity region, and a third region where the piezoelectric substrate, the first excitation electrode, and the second excitation electrode overlap with the second part of the mass-adding film is defined as a second low acoustic velocity region
Implementation Method 2
a piezoelectric substrate having a first main surface that extends in a first direction and a second direction intersecting the first direction, and a second main surface facing the first main surface; a first excitation electrode on the first main surface of the piezoelectric substrate
Data Source
AI summary
A piezoelectric vibration element that includes: a piezoelectric substrate; a first excitation electrode on a first main surface of the piezoelectric substrate; a second excitation electrode on a second main surface of the piezoelectric substrate; and a mass-adding film at least a part of which overlaps with the first excitation electrode, the mass-adding film including a first part and a second part which do not overlap a central portion of the first excitation electrode, the first part extends along a first outer edge portion of the first excitation electrode and the second part extends along a second outer edge portion of the first excitation electrode so as to define a high acoustic velocity region, a first low acoustic velocity region, and a second low acoustic velocity region in a plan view.