Elastic Wave Filter Busbar Segmentation for Close IDT Spacing
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Solution Overview
Problem
The challenge in elastic wave devices is the likelihood of formation failures or defects in busbars when IDT electrodes with a two-layer structure are arranged closely, leading to potential short-circuiting and hindering size reduction.
Innovation Solution
The design includes IDT electrodes with busbars featuring a first and second electrode layer, 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 by incorporating serial and parallel arm resonators.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If IDT electrodes with two-layer busbar structure are arranged closely to reduce device size, then device size is reduced, but formation failures or defects in busbars occur more frequently
Solution Approach 1:
The second electrode layer of the second busbar is divided into multiple segments by cutting it at multiple locations in the direction crossing the elastic-wave propagating direction. This segmentation isolates potential defects to individual segments, preventing defect propagation across the entire busbar length, thereby maintaining reliability in closely arranged IDT electrodes
Solution Approach 2:
The cutting of the second electrode layer is applied specifically to the second busbar rather than all busbars, creating local structural differentiation. This targeted modification addresses the reliability issue in critical regions where IDT electrodes are closely arranged, while maintaining the integrity of other busbar structures
2Area of stationary object
If IDT electrodes are arranged closely in direction perpendicular to elastic-wave propagating direction, then device size is reduced, but short-circuiting between adjacent busbars occurs
Solution Approach 1:
By cutting the second electrode layer of the second busbar at multiple locations, the continuous conductive path is divided into isolated segments. This prevents potential short-circuiting between adjacent busbars by ensuring that even if insulation fails in one location, the electrical fault cannot propagate across the entire busbar length
Solution Approach 2:
The cuts in the second electrode layer act as intermediary insulating barriers between adjacent busbars. These cut regions create electrical isolation zones that prevent direct conductive paths between the second busbar and adjacent busbars, thereby maintaining electrical insulation in closely arranged configurations
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, enhances filter characteristics, and enables further size reduction of the elastic wave device without increasing insertion losses.
Implementation Method 1
an elastic wave device includes a piezoelectric substrate, and a plurality of elastic wave elements provided on the piezoelectric substrate
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.