IDT Busbar Cut Structure for Compact Elastic Wave Filters

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Solution Overview

Problem

Elastic wave devices face challenges in size reduction due to increased risk 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 elastic wave device 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 while maintaining improved filter characteristics.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Volume of moving object

If the distance between adjacent busbars is decreased to enable closer arrangement of IDT electrodes, then the device size is reduced, but the risk of formation failures or defects in busbars increases, leading to potential short-circuiting

Engineering Contradiction:

Improvedevice sizeVSAvoidbusbar formation reliability

Core Design Contradiction:

Volume of moving objectVSReliability

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 prevents continuous defects from causing short-circuits between adjacent busbars, allowing the busbars to be arranged closer together while maintaining reliability.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The second electrode layer is selectively removed (cut) at specific locations between the first and second busbars. This extraction creates isolation regions that prevent defect propagation and eliminate the risk of short-circuiting, enabling closer spacing of the busbars.

Inventive Principle:

Principle #2Taking out (Extraction)

2Area of stationary object

If the busbars are arranged closer together to reduce device size, then the area occupied by the device is reduced, but the likelihood of short-circuiting between adjacent busbars increases

Engineering Contradiction:

Improvedevice areaVSAvoidshort-circuit risk

Core Design Contradiction:

Area of stationary objectVSObject-affected harmful factors

Solution Approach 1:

The cut portions of the second electrode layer act as intermediary isolation regions between adjacent busbars. These intermediary structures prevent direct electrical contact between busbars even when they are closely spaced, thereby eliminating the harmful short-circuit effect while allowing minimal spacing.

Inventive Principle:

Principle #24Intermediary (Mediator)

3Reliability

If the IDT electrodes are arranged in a horizontally elongated configuration to improve filter characteristics, then the busbar length increases, but the risk of formation failures or defects in busbars increases

Engineering Contradiction:

Improvefilter characteristicsVSAvoidbusbar formation precision

Core Design Contradiction:

ReliabilityVSManufacturing precision

Solution Approach 1:

By cutting the second electrode layer at multiple locations along the length of the busbar, the continuous electrode structure is segmented into isolated sections. This segmentation prevents defects from propagating across the entire busbar length, thereby improving manufacturing precision and yield even when the busbar length is increased for better filter characteristics.

Inventive Principle:

Principle #1Segmentation

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, enables closer packing of IDT electrodes, and enhances filter characteristics, allowing for a more compact elastic wave device without compromising performance.

Implementation Method 1

a piezoelectric substrate, and a plurality of elastic wave elements provided on the piezoelectric substrate and including IDT electrodes

Methodology Applied

Scientific EffectPiezoelectric effect: Piezoelectric Effect

Data Source

PatentUS10418966B2Elastic wave device having a cut in a busbar electrode layer

Publication Date: 2019.09.17 MURATA MFG CO LTD

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.