Acoustic Wave Electrode Layout for Crack-Resistant Busbars
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
In acoustic wave devices, stress concentration between the intersection region and the busbar can lead to crack formation, causing electrode finger breakage and changes in filter characteristics.
Innovation Solution
The acoustic wave device includes a support with a cavity portion overlapping the intersection region, and busbar portions with protruding electrodes that extend towards the intersection region, dispersing stress and reducing crack extension.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the support body is provided with a through-hole and the piezoelectric layer covers the through-hole to form a membrane portion, then the device structure is simplified and manufacturing is easier, but stress concentrates between the intersection region and the busbar causing crack formation and electrode finger breakage
Solution Approach 1:
The patent applies local quality by providing recesses in the busbar portions at positions facing the cavity portion. This local structural modification concentrates stress relief at the critical location where cracks would otherwise form and propagate, without requiring changes to the overall device structure or manufacturing process. The recesses create a stress-distributing geometry that prevents crack initiation at the busbar-piezoelectric layer interface.
Solution Approach 2:
The patent implements beforehand cushioning by pre-configuring the busbar portions with recesses that anticipate and prevent crack formation. These recesses act as stress-relief features that are built into the structure before operation, cushioning against the concentration of stress that would otherwise lead to crack propagation between the intersection region and the busbar.
2Device complexity
If the membrane portion is used to simplify the structure, then device complexity is reduced, but crack extension occurs more easily between the intersection region and the busbar
Solution Approach 1:
The recesses in the busbar portions provide localized stress management at the critical interface region. This local structural feature strengthens the bond between the busbar and piezoelectric layer without adding overall device complexity, as the recesses are integrated into the existing busbar geometry rather than requiring additional components or layers.
Solution Approach 2:
The patent addresses the strength issue by introducing a vertical dimension feature (recesses) into the busbar structure. This dimensional modification changes the stress distribution profile from a planar concentration to a three-dimensional gradient, reducing peak stresses at the interface without affecting the horizontal layout or overall device footprint.
3Reliability
If electrode fingers are broken due to crack extension, then the electrical connection is compromised, but adding more protective structures increases device complexity
Solution Approach 1:
The recesses in the busbar portions provide targeted protection at the critical stress concentration points without requiring comprehensive protective structures across the entire device. This localized approach maintains electrical connection reliability by preventing crack propagation at the busbar interface while avoiding the addition of complex protective layers or structures over the electrode fingers themselves.
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 reduces or prevents the extension of cracks, minimizing electrode finger breakage and maintaining the electrical characteristics of the acoustic wave device.
Implementation Method 1
a piezoelectric layer on the support and including a first main surface and a second main surface facing each other, and an IDT electrode on at least one of the first main surface and the second main surface of the piezoelectric layer... By applying an AC voltage to the IDT electrode, a bulk wave in a thickness-shear mode is excited.
Data Source
AI summary
An acoustic wave device includes a support, a piezoelectric layer including first and second main surfaces, and an IDT electrode including first and second busbar portions, and first and second electrode fingers connected to the first and second busbar portions and being interdigitated with each other. A region in which first and second electrode fingers adjacent to each other overlap each other is an intersection region. A cavity portion is provided in the support and overlaps the intersection region. At least one of the first and second busbar portions includes an outer busbar not overlapping the cavity portion, and at least one of protruding electrodes extending from the outer busbar toward the intersection region. The at least one protruding electrode overlaps an outer peripheral edge of the cavity portion.