Elastic Boundary Wave Substrate for Compact SAW Filters
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Solution Overview
Problem
Elastic surface wave filters require packaging to maintain free surface and propagation path, leading to larger element sizes and limitations in energy confinement within the substrate.
Innovation Solution
A substrate structure is developed with a metal electrode, dielectric thin films, and a piezoelectric substrate, where energy is concentrated near the boundary surface to minimize radiation and displacement, enhancing electromechanical coupling and temperature stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If elastic surface wave filters use free surface propagation paths, then wave propagation is enabled, but packaging is required which increases element size
Solution Approach 1:
The patent extracts the wave propagation function from the surface and confines it within the substrate by utilizing elastic boundary waves that propagate along the interface between the piezoelectric substrate and the thin film, eliminating the need for free surface propagation and packaging
Solution Approach 2:
The patent nests the wave propagation path within the substrate structure itself by forming a thin film on the piezoelectric substrate, creating a confined propagation path that eliminates the need for external packaging while maintaining wave propagation functionality
2Volume of moving object
If energy is confined into substrate using elastic boundary wave, then packaging is eliminated, but conditions for trapping boundary wave are strict requiring monolayered thin film
Solution Approach 1:
The patent changes the structural parameter from monolayered to multilayered thin films, demonstrating that boundary waves can be effectively trapped and confined using multiple dielectric layers with different acoustic impedances, thereby relaxing the strict monolayer requirement while maintaining energy confinement
Solution Approach 2:
The patent employs composite multilayered dielectric structures on the piezoelectric substrate, where each layer is designed with specific acoustic properties to create effective boundary wave trapping, replacing the simple monolayer structure with a more flexible composite architecture
3Power
If thin film surface displacement is produced, then electromechanical coupling occurs, but energy radiation to substrate increases
Solution Approach 1:
The patent applies local quality by creating a multilayered dielectric structure where each layer has specific acoustic impedance properties that locally control wave confinement, allowing electromechanical coupling at the interface while preventing energy radiation through the substrate by designing layers with progressively different properties
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 solution achieves a compact filter design with improved electromechanical coupling and temperature stability by confining energy within the substrate, reducing the need for packaging and minimizing energy radiation.
Implementation Method 1
an elastic boundary wave substrate on which energy is concentrated into a substrate surface and an electrode section
Implementation Method 2
a structure wherein a metal electrode, a dielectric thin film and a further dielectric thin film are adhered onto a piezoelectric substrate
Data Source
AI summary
The structure of the patent is a substrate wherein a metal electrode, a dielectric thin film, and a further dielectric thin film are adhered onto a piezoelectric substrate. A substrate wherein elastic wave energy is confined in the piezoelectric substrate can be obtained. In particular, when a SiO2 thin film and an AlN thin film are used as thin films 4 and 5, respectively, a substrate excellent in an electromechanical coupling coefficient (k2) and a temperature characteristic of frequency can be yielded by making the film thicknesses of electrodes 2 and 3 and those of the thin films 4 and 5 into optimal values.