Acoustic Wave Resonator Mass Film Layout for Spurious Suppression
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Solution Overview
Problem
Existing acoustic wave devices using piezoelectric members with anisotropic properties fail to sufficiently suppress spurious responses.
Innovation Solution
The acoustic wave device incorporates a piezoelectric member with anisotropic properties and includes a first and second electrode, with an additional mass film on at least one of the electrodes, where the configuration of the additional mass film portions on different sides of the piezoelectric member's plane are varied to compensate for anisotropy, reducing spurious responses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a piezoelectric member with anisotropic properties is used, then the device can utilize the specific directional characteristics of the material, but spurious responses are not sufficiently suppressed
Solution Approach 1:
The patent applies local quality by making the electrode thickness non-uniform across different regions. Specifically, the electrode has a first thickness in a first region and a second thickness in a second region, allowing different parts of the electrode to serve different functions in suppressing spurious responses while accommodating the anisotropic properties of the piezoelectric member
Solution Approach 2:
The patent employs asymmetry by creating an asymmetric electrode structure where the thickness varies between regions. This asymmetric configuration is designed to counterbalance the anisotropic properties of the piezoelectric member, thereby suppressing spurious responses that arise from the directional dependence of the material
2Reliability
If the electrode thickness is made non-uniform to suppress spurious responses, then resonance characteristics improve, but device complexity increases
Solution Approach 1:
The patent applies parameter changes by varying the thickness parameter of the electrode across different regions. This continuous parameter variation allows for optimization of resonance characteristics and suppression of spurious responses while maintaining a relatively simple overall electrode structure that can be fabricated using standard techniques
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 spurious responses by optimizing the additional mass film structure to match the anisotropic properties of the piezoelectric member, resulting in improved resonance characteristics.
Implementation Method 1
a piezoelectric member including a first main surface and a second main surface opposing each other
Implementation Method 2
an acoustic reflection section on a surface of the second electrode different from a surface of the second electrode on the piezoelectric member
Data Source
AI summary
An acoustic wave device includes a piezoelectric member, a first and second electrodes on first and second main surfaces of the piezoelectric member, an acoustic reflection section including an air gap, and an additional mass film in at least one of areas on the first and second electrodes and an area outward of the first or second electrodes. A region where at least one of the first electrode and the additional mass film overlaps the second electrode includes a first region and a second region surrounding the first region. In the second region, a configuration of additional mass film portions on corresponding sides of a first direction in a plane of the piezoelectric member and a configuration of additional mass film portions on corresponding sides of a second direction in the plane of the piezoelectric member are different from each other.