Elastic Wave Electrode Layout to Prevent Passband Ripple
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Solution Overview
Problem
Elastic wave devices suffer from ripple generation in the pass band due to electric charge stagnation and surge breakdown during the formation of IDT electrodes, leading to variability in ripple frequencies and magnitudes.
Innovation Solution
The elastic wave device design includes a piezoelectric film directly or indirectly laminated on a high acoustic velocity member, with a close contact layer improving adhesiveness, and conductive films used to define IDT electrodes and connection wiring, reducing the area of the first conductive film and minimizing surge breakdown and ripple generation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If a low acoustic velocity film formed with insulation material is provided under the piezoelectric film, then electric charge stagnation is reduced, but surge breakdown occurs between IDT electrode components
Solution Approach 1:
A close contact layer is introduced as an intermediary between the piezoelectric film and the low acoustic velocity film. This close contact layer serves as a mediator that prevents both electric charge stagnation and surge breakdown by providing a controlled interface that manages electrical field distribution while maintaining acoustic wave propagation characteristics.
Solution Approach 2:
The invention modifies the structural parameters of the film stack by introducing the close contact layer with specific material properties and thickness. This parameter change alters the electrical field distribution and charge accumulation characteristics, preventing surge breakdown while maintaining the low acoustic velocity film's ability to reduce charge stagnation.
2Volume of moving object
If the thickness of the piezoelectric film is small, then device size is reduced, but electric charge stagnation increases causing surge breakdown
Solution Approach 1:
The invention creates a composite structure consisting of the piezoelectric film, close contact layer, and low acoustic velocity film. This composite material system allows the thin piezoelectric film to maintain small device size while the combined structure prevents charge stagnation through the specialized properties of the close contact layer and low acoustic velocity film.
3Ease of manufacture
If connection wiring is defined by the first conductive film, then manufacturing process is simplified, but surge breakdown occurs and ripples are generated in pass band
Solution Approach 1:
The conductive films are segmented into different functional layers: the first conductive film defines the IDT electrodes while the second conductive film defines the connection wiring. This segmentation allows each conductive film to be optimized for its specific function, preventing surge breakdown and ripple generation while maintaining manufacturing simplicity through sequential formation processes.
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 prevents ripple generation in the pass band, enhances adhesiveness, and reduces the risk of surge breakdown, leading to improved frequency characteristics and increased Q-value.
Implementation Method 1
a piezoelectric film, a first conductive film provided on the piezoelectric film, and a second conductive film provided on the piezoelectric film and on at least a portion of the first conductive film
Implementation Method 2
a high acoustic velocity member in which an acoustic velocity of a bulk wave propagating in the high acoustic velocity member is larger than an acoustic velocity of a main mode elastic wave propagating in the piezoelectric film
Data Source
AI summary
An elastic wave device includes a piezoelectric film and a high acoustic velocity member in which an acoustic velocity of a bulk wave propagating in the high acoustic velocity member is larger than an acoustic velocity of a main mode elastic wave propagating in the piezoelectric film, the piezoelectric film that is directly or indirectly laminated on the high acoustic velocity member, a first conductive film provided on the piezoelectric film, and a second conductive film that is provided on the piezoelectric film and on at least a portion of the first conductive film. A plurality of IDT electrodes including electrode fingers and busbars are provided on the piezoelectric film, at least electrode fingers of a plurality of IDT electrodes are defined by the first conductive film, and at least a portion of connection wiring with which the plurality of IDT electrodes are connected to each other is defined the second conductive film.