Acoustic Wave Filter Ground Wiring Layout for Lower Coupling
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Solution Overview
Problem
Existing acoustic wave filters face issues with electromagnetic coupling between wiring portions on a piezoelectric substrate, leading to signal propagation between non-physically connected wiring portions, which results in deteriorated attenuation characteristics.
Innovation Solution
An acoustic wave filter design featuring a piezoelectric substrate with a functional electrode and first wiring portion, a mounting substrate with a second wiring portion connected to ground, where the inter-wiring distance is less than the wiring width of the first wiring portion, reducing electromagnetic coupling and improving attenuation characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If wiring portions are placed close together on the piezoelectric substrate, then device integration is improved, but electromagnetic coupling between wiring portions increases causing signal propagation between non-physically connected wiring portions
Solution Approach 1:
A ground wiring portion is introduced as an intermediary element between signal wiring portions on the piezoelectric substrate and the mounting substrate. This ground wiring acts as a mediator that provides electromagnetic shielding, preventing harmful electromagnetic coupling between adjacent signal wirings while maintaining compact device integration.
Solution Approach 2:
The harmful electromagnetic coupling effect is extracted and redirected by introducing dedicated ground wiring portions that are electrically connected to ground potential. By separating the ground function into distinct wiring portions, the patent eliminates the harmful electromagnetic interaction between signal-carrying wirings while preserving close spacing for high integration.
2Area of stationary object
If wiring portions are placed close together, then space utilization is improved, but attenuation characteristics deteriorate due to signal propagation between non-physically connected wiring portions
Solution Approach 1:
Ground wiring portions are positioned between signal wiring portions to act as electromagnetic shields. This intermediary ground wiring prevents unwanted signal propagation while maintaining close spacing between functional wirings, thus preserving both compact space utilization and proper attenuation characteristics.
Solution Approach 2:
The patent utilizes the vertical dimension by placing ground wiring portions on both the piezoelectric substrate and the mounting substrate, creating a three-dimensional electromagnetic shielding structure. This multi-layer approach effectively blocks electromagnetic coupling while allowing horizontal wiring spacing to remain compact for good space utilization.
3Object-generated harmful factors
If ground wiring portion is added between first wiring portion and mounting substrate, then electromagnetic coupling is reduced, but device complexity increases
Solution Approach 1:
The ground wiring portions on the piezoelectric substrate and mounting substrate are electrically connected through via holes, merging them into a unified ground reference system. This integration reduces device complexity by creating a coordinated electromagnetic shielding structure rather than treating each ground wiring as an independent element.
Solution Approach 2:
The ground wiring portions serve multiple functions: they provide electromagnetic shielding between signal wirings, establish a common ground reference potential, and enable electrical connection between substrates. This multi-functionality reduces the need for additional dedicated shielding structures, thereby limiting the increase in device complexity.
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 configuration effectively reduces electromagnetic coupling between wiring lines, ensuring that signals pass through the filter properly, thereby enhancing the attenuation characteristics of the acoustic wave filter.
Implementation Method 1
a wiring portion on a piezoelectric substrate becomes electromagnetically coupled to another wiring portion on the piezoelectric substrate
Data Source
AI summary
An acoustic wave filter includes a piezoelectric substrate, a functional electrode, a first wiring portion, a mounting substrate, and a second wiring portion. The functional electrode and the first wiring portion are located at a first major surface of the piezoelectric substrate. The first wiring portion is connected to the functional electrode. The second wiring portion is located at a third major surface of the mounting substrate. The second wiring portion is connected to ground. The first major surface of the piezoelectric substrate, and the third major surface of the mounting substrate are opposite to each other. An inter-wiring distance is less than a wiring width of the first wiring portion. The inter-wiring distance is a distance between the first wiring portion, and a portion of the second wiring portion that overlaps the first wiring portion in plan view seen in the direction of thickness of the mounting substrate.