Acoustic Wave Filter Busbar Layout With Through-Electrode Connections
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Solution Overview
Problem
Filter characteristics in acoustic wave resonators with IDT electrodes on both major surfaces of a piezoelectric layer are prone to deterioration due to improper wire connection positioning.
Innovation Solution
A filter device with a plurality of acoustic wave resonators featuring through electrodes that connect busbars of IDT electrodes across major surfaces, reducing electrical resistance and phase differences, thereby maintaining symmetry and preventing filter characteristic deterioration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If IDT electrodes are provided on both major surfaces of a piezoelectric layer, then filter characteristics can be improved, but wire connection positioning becomes complex and filter characteristics deteriorate unless properly located
Solution Approach 1:
The patent introduces through electrodes that extend vertically through the piezoelectric layer, adding a vertical connection dimension. This allows wire connections to be made from the upper surface through the layer rather than requiring precise positioning on the lower surface, effectively moving the connection problem from a 2D planar constraint to a 3D volumetric solution.
Solution Approach 2:
The through electrodes act as intermediary elements that mediate the connection between upper and lower wire connections. Instead of directly connecting wires on opposite surfaces (which requires precise positioning), the through electrodes serve as intermediate conductive paths that simplify the connection geometry and reduce positioning constraints.
2Reliability
If through electrodes are used to connect busbars across major surfaces, then connection reliability improves, but manufacturing complexity increases
Solution Approach 1:
The patent merges the through electrode formation with the IDT electrode fabrication process. The through electrodes are formed simultaneously with the IDT electrodes using the same sputtering and patterning steps, eliminating separate manufacturing operations and reducing overall manufacturing complexity despite the added structural feature.
Solution Approach 2:
The through electrodes serve multiple functions: they provide mechanical support, establish electrical connections, and define the acoustic wave path. This multi-functionality reduces the need for additional separate components or processes, thereby simplifying the overall manufacturing system despite the added complexity of the through-electrode structure.
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 effectively reduces insertion loss and spurious components by ensuring reliable and easy connection of IDT electrodes, enhancing filter performance.
Implementation Method 1
a piezoelectric substrate including a piezoelectric layer with a first major surface and a second major surface located opposite from each other
Implementation Method 2
a first IDT electrode on the first major surface, and a second IDT electrode on the second major surface
Data Source
AI summary
A filter device includes acoustic wave resonators each including a piezoelectric substrate including a piezoelectric layer with first and second major surfaces, a first IDT electrode on the first major surface, and a second IDT electrode on the second major surface, and through electrodes penetrating the piezoelectric layer. Continuous circuits including acoustic wave resonators each including the first and second IDT electrodes are continuously connected. Each of the first and second IDT electrodes of the acoustic wave resonators includes a pair of busbars. The continuous circuits include wires each including the busbars. The wires located at ends of the continuous circuits are each an end portion wire including the busbars of the first and second IDT electrodes in each of the acoustic wave resonators provided with the busbars included in the end portion wires are connected by the through electrode.