IDT Busbar Segmentation for Compact Elastic Wave Filters
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Solution Overview
Problem
Elastic wave devices face challenges in size reduction due to increased likelihood of formation failures or defects in busbars of IDT electrodes, leading to potential short-circuiting when arranged closely, which hinders further miniaturization and improves filter characteristics.
Innovation Solution
The design incorporates IDT electrodes with busbars featuring a two-layer electrode structure, where the second electrode layer is cut perpendicular to the elastic-wave propagating direction, reducing the likelihood of defects and allowing for closer arrangement and size reduction of elastic wave devices.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If elastic wave resonators are arranged closer to each other in the direction perpendicular to elastic-wave propagating direction, then device size is reduced, but formation failures or defects in busbars occur more frequently leading to short-circuiting
Solution Approach 1:
The second electrode layer of the second busbar is divided into multiple segments by cutting it at one or more positions along the elastic-wave propagating direction. This segmentation prevents continuous defects from causing short-circuits between adjacent busbars, enabling closer arrangement of elastic wave resonators while maintaining reliability
Solution Approach 2:
The problematic continuous second electrode layer is extracted and removed at specific positions through cutting. This eliminates the risk of defect propagation in the overlapping region between adjacent busbars, allowing for reduced device size without compromising busbar formation reliability
2Volume of moving object
If busbars are made with two-layer structure and arranged closely, then device size is reduced, but manufacturing precision requirements increase due to higher likelihood of formation defects
Solution Approach 1:
By segmenting the second electrode layer through cutting, the patent reduces the continuous length where manufacturing defects can occur. This allows for closer busbar arrangement while tolerating higher variability in manufacturing precision, as defects are confined to smaller segments rather than propagating across the entire busbar length
3Volume of moving object
If IDT electrodes are arranged in sufficiently close relation for size reduction, then device miniaturization is achieved, but short-circuiting between adjacent busbars becomes more likely
Solution Approach 1:
The harmful continuous conductive path in the second electrode layer is extracted and removed at cutting positions. This eliminates the mechanism that would cause short-circuiting between adjacent busbars, enabling the IDT electrodes to be arranged in sufficiently close relation for device miniaturization without the risk of short-circuits
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 minimizes defects in busbars, enabling the reduction of elastic wave device size while maintaining or improving filter characteristics by reducing electrical resistance and preventing short-circuiting, thus enhancing the device's performance and miniaturization potential.
Implementation Method 1
a piezoelectric substrate, and a plurality of elastic wave elements provided on the piezoelectric substrate and including IDT electrodes
Data Source
AI summary
An elastic wave device includes a piezoelectric substrate, and elastic wave elements on the piezoelectric substrate and including IDT electrodes, respectively. The IDT electrode of a first of the elastic wave elements includes first and second busbars, and the IDT electrode of a second of the elastic wave elements includes third and fourth busbars. The second busbar and the third busbar extend parallel or substantially parallel to each other, and are spaced by a gap in a direction perpendicular or substantially perpendicular to an elastic-wave propagating direction. Each of the second and third busbars includes first and second electrode layers at least a portion of which is laminated on the first electrode layer. The second electrode layer of the second busbar is cut in at least one location in a direction crossing the elastic-wave propagating direction.