Elastic Wave Filter Layout Using Region-Specific Dielectric Thickness
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing elastic wave devices face challenges in improving productivity and reducing insertion loss, particularly due to the need for multiple processes to form IDT electrodes with different film thicknesses, which can decrease efficiency.
Innovation Solution
The elastic wave device features first to third IDT electrodes on a piezoelectric substrate with a dielectric film covering them, where the dielectric film thickness varies across regions, and the IDT electrodes have different electrode finger pitches and materials, allowing for equal or substantially equal density equivalent thicknesses for the first and second electrodes while differing from the third, thereby optimizing the ratio of dielectric film thickness to electrode finger pitch for each.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If IDT electrodes of multiple elastic wave filters are formed in different processes to achieve different film thicknesses, then insertion losses are reduced, but productivity is decreased due to multiple formation processes
Solution Approach 1:
The patent merges the formation processes of multiple IDT electrodes into a single simultaneous formation process. By providing first, second, and third IDT electrodes that can be formed together in one process step, the patent eliminates the need for multiple separate formation processes while still achieving different film thicknesses through the use of a thickness conversion table that accounts for material density differences.
Solution Approach 2:
The patent changes the parameter of film thickness by controlling the thickness of the dielectric film in different regions rather than changing the IDT electrode thickness. By making the dielectric film thickness different in regions where different IDT electrodes are located, the patent achieves different effective thicknesses for each filter element while forming all IDT electrodes simultaneously.
2Loss of energy
If IDT electrodes have different film thicknesses to optimize filter characteristics, then insertion losses are reduced, but device complexity increases due to multiple thickness specifications
Solution Approach 1:
The patent applies local quality by making the dielectric film thickness vary in different regions of the substrate. Specifically, the dielectric film has a first thickness in the first region, a second thickness in the second region, and a third thickness in the third region, allowing each IDT electrode to have optimized characteristics for its specific function while using the same base formation process.
Solution Approach 2:
The patent introduces the dielectric film as an intermediary element that mediates between the uniform IDT electrode formation process and the required different thickness specifications. By controlling the dielectric film thickness rather than the IDT electrode thickness directly, the patent achieves thickness differentiation without increasing the complexity of the IDT formation process.
3Manufacturing precision
If multiple processes are used to form IDT electrodes with different thicknesses, then filter characteristics are optimized, but manufacturing time increases
Solution Approach 1:
The patent performs preliminary action by providing a thickness conversion table in advance that correlates dielectric film thickness with effective IDT electrode thickness. This table, which accounts for material density differences, allows the manufacturing process to directly specify dielectric film thickness without requiring multiple iterative IDT formation processes, thereby reducing manufacturing time while maintaining precision.
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 insertion losses and enhances productivity by allowing for the use of suitable materials for each IDT electrode, improving filter characteristics and manufacturing efficiency.
Implementation Method 1
an elastic wave device according to a preferred embodiment of the present invention includes a piezoelectric substrate
Data Source
AI summary
An elastic wave device includes a piezoelectric substrate, first to third IDT electrodes provided on the piezoelectric substrate, a dielectric film provided on the piezoelectric substrate and covering the first to third IDT electrodes, the thickness of the dielectric film in a first region in which the dielectric film covers the first IDT electrodes is different from the thickness of the dielectric film in a second region in which the dielectric film covers the second IDT electrodes and the thickness of the dielectric film in a third region in which the dielectric film covers the third IDT electrodes. The density equivalent thickness of each of the first IDT electrodes and the second IDT electrodes are equal to each other, and the density equivalent thickness of each of the third IDT electrodes is different from the density equivalent thickness of each of the first IDT electrodes and the second IDT electrodes.