Acoustic Wave Electrode Layout Over a Cavity to Suppress Ripple
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Solution Overview
Problem
Acoustic wave devices with piezoelectric substrates experience deterioration in characteristics due to undesired ripples caused by electrodes connected to different potentials, leading to performance issues.
Innovation Solution
The design includes a piezoelectric layer with electrodes that overlap a cavity portion when viewed from the laminating direction, preventing leakage waves and thus reducing ripple effects, along with a manufacturing method that forms a terminal hole and pad electrode to enhance the device's structural integrity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If electrodes connected to different potentials are disposed adjacent to each other on the same surface of the piezoelectric substrate, then the device structure is simplified and manufacturing is easier, but undesired ripple occurs between the electrodes leading to deterioration in characteristics
Solution Approach 1:
The patent transitions from planar electrode arrangement to a three-dimensional configuration where wiring electrodes are positioned at different heights (on upper and lower surfaces of the piezoelectric substrate). This vertical separation in the thickness direction prevents direct adjacency of electrodes with different potentials, eliminating ripple formation while maintaining manufacturing feasibility through layered construction.
Solution Approach 2:
The patent introduces an insulating film as an intermediary layer between electrodes connected to different potentials. This insulating barrier prevents direct electromagnetic interaction and ripple formation between adjacent electrodes, allowing simplified manufacturing while protecting device characteristics from deterioration.
2Reliability
If electrodes are arranged to avoid ripple formation, then characteristics are improved, but device structure becomes more complex
Solution Approach 1:
The patent uses the thickness direction (vertical dimension) to separate wiring electrodes from functional electrodes, arranging them on opposite surfaces of the piezoelectric substrate. This three-dimensional arrangement prevents ripple formation through spatial separation without requiring complex lateral configurations or additional structural elements.
Solution Approach 2:
The patent divides the electrode system into functionally distinct groups: functional electrodes on one surface and wiring electrodes on the opposite surface. This segmentation allows each electrode type to perform its specific function while preventing harmful interactions, achieving characteristic improvement through systematic organization rather than structural complexity.
3Reliability
If wiring electrodes are positioned to overlap the cavity portion, then ripple is reduced, but manufacturing precision requirements increase
Solution Approach 1:
The patent positions wiring electrodes on the lower surface of the piezoelectric substrate to overlap the cavity portion in plan view, while functional electrodes are on the upper surface. This vertical separation allows the wiring electrodes to be precisely positioned relative to the cavity without affecting functional electrode placement, as they operate in different spatial planes, thereby reducing ripple while managing manufacturing precision 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
This configuration effectively reduces or prevents the deterioration of characteristics in acoustic wave devices by minimizing ripple formation, leading to improved performance and reliability.
Implementation Method 1
acoustic wave devices each of which includes a piezoelectric layer made of lithium niobate or lithium tantalate
Data Source
AI summary
An acoustic wave device includes a piezoelectric layer, a support substrate, at least a first and a second functional electrode and a wiring electrode connected to each of the functional electrodes. The wiring electrode includes one or more first wiring electrodes connected to the first and second functional electrodes. A cavity portion is located between the support substrate and the piezoelectric layer. An entirety of the first functional electrode and an entirety of a first wiring electrode connected to the first functional electrode are located on at least one of the first main surface and the second main surface of the piezoelectric layer in an overlapping manner with the cavity portion when viewed from a laminating direction of the support substrate and the piezoelectric layer.