Elastic Wave Device Wiring Layout to Suppress Spurious Bulk Waves
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Solution Overview
Problem
Elastic boundary wave devices suffer from poor electrical characteristics due to high-frequency spurious components caused by unwanted bulk waves, which are generated when the second wiring portion overlaps with the IDT electrodes, leading to suboptimal filter characteristics.
Innovation Solution
The second wiring portion is arranged over an area other than where the IDT electrodes or their interdigitated portions are located, preventing the generation of high-frequency spurious components and improving electrical characteristics by minimizing unwanted wave excitation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the second wiring portion is routed on the upper surface of the dielectric layer to electrically connect portions with the shortest possible length, then the device size is reduced, but high-frequency spurious components caused by unwanted bulk waves occur, resulting in poor filter characteristics
Solution Approach 1:
The second wiring portion is extracted from the area over the IDT electrodes by routing it on the insulating film instead. This separation removes the source of spurious component generation while maintaining electrical connectivity through the insulating film substrate, thus reducing device size without compromising filter characteristics.
Solution Approach 2:
The insulating film serves as an intermediary medium that allows the second wiring portion to be routed above the IDT electrode area without direct contact. This mediator enables short wiring paths for size reduction while preventing the generation of unwanted bulk waves that would occur with direct wiring over the electrodes.
2Device complexity
If the second wiring portion is arranged over the IDT electrode area to achieve shortest wiring length, then wiring density is improved, but unwanted waves such as bulk waves are excited, causing low filter characteristics
Solution Approach 1:
The second wiring portion is extracted from the harmful zone over the IDT electrodes. By routing it on the insulating film, the wiring maintains high density and short length while being removed from the area that generates spurious components, thus eliminating the harmful effect without sacrificing wiring efficiency.
Solution Approach 2:
The insulating film provides different local properties: it acts as an electrical insulator and mechanical support in the wiring area, while also serving as a substrate that prevents wave excitation when the wiring is routed on it. This local quality differentiation allows high-density wiring without spurious component generation.
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 arrangement significantly enhances filter characteristics and resonance performance by eliminating spurious frequency components, resulting in improved electrical characteristics and reduced device size without compromising wiring density.
Implementation Method 1
an elastic wave device including a piezoelectric substrate (11)
Implementation Method 2
an insulating film (12) arranged so as to cover the at least one IDT electrode (21 to 23) and the first wiring portion (41)
Data Source
AI summary
An elastic wave device that suppresses high-frequency spurious components caused by unwanted waves, such as bulk waves, and improves filter characteristics, includes a piezoelectric substrate, an electrode structure including an IDT electrode provided on the substrate, a first wiring portion that is electrically connected to the IDT electrode, and a second wiring portion provided on a first insulating film that includes a through-hole partially exposing the first wiring portion therethrough. The second wiring portion extends into the through-hole and is electrically connected to the first wiring portion. The second wiring portion is arranged over an area other than the area in which the IDT electrode is disposed.