Layered Al-Cu Electrode Structure for Durable Acoustic Wave Devices
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Solution Overview
Problem
Existing acoustic wave devices face issues with increased electrical resistance and deteriorating characteristics when copper concentration in the electrode is increased to improve power durability.
Innovation Solution
The acoustic wave device incorporates a layered electrode structure with a first layer containing Al and CuAl2 crystal grains orthogonal to the substrate's thickness direction, and a second layer with Cu concentration controlled to prevent CuAl2 grains from extending to the main surface, thereby improving power durability while minimizing resistance increase.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If copper concentration in the electrode is increased to improve power durability, then power durability is improved, but electrical resistance increases and characteristics deteriorate
Solution Approach 1:
The electrode is divided into multiple layers with different Cu concentrations and compositions. The first layer (closest to piezoelectric substrate) has higher Cu concentration for power durability, while subsequent layers have lower Cu concentration to maintain low electrical resistance. This local differentiation resolves the contradiction by optimizing each layer's composition for its specific functional requirement.
Solution Approach 2:
The electrode uses a composite multi-layer structure combining Al-Cu alloys with different Cu concentrations. This composite approach allows the electrode to simultaneously achieve high power durability (from Cu-rich first layer) and low electrical resistance (from Al-rich upper layers), resolving the contradiction through material composition optimization.
2Reliability
If copper concentration is increased to improve power durability, then power durability is improved, but characteristics of the surface acoustic wave element deteriorate
Solution Approach 1:
Different layers of the electrode are assigned different Cu concentrations tailored to their specific functional roles. The first layer near the substrate uses higher Cu content for power durability, while upper layers use lower Cu content to preserve acoustic wave characteristics, thus resolving the contradiction through spatially differentiated material properties.
Solution Approach 2:
The multi-layer Al-Cu composite electrode structure enables simultaneous optimization of power durability and acoustic characteristics by combining materials with different Cu concentrations in a stratified configuration, where each layer contributes its optimal properties to the overall performance.
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 enhances power durability and reduces characteristic degradation by optimizing the distribution of CuAl2 crystal grains, maintaining electrical performance.
Implementation Method 1
a surface acoustic wave element including a piezoelectric substrate and an electrode formed on the piezoelectric substrate
Data Source
AI summary
An acoustic wave device includes a piezoelectric substrate and an electrode on the piezoelectric substrate and including first and second layers. The first layer includes Al and Cu. The second layer is on a side opposite to a piezoelectric substrate side of the first layer and includes Al. The first layer includes an Al crystal and at least a portion of CuAl2 crystal grains that are provided in a direction orthogonal or substantially orthogonal to a thickness direction of the piezoelectric substrate. In the electrode, the CuAl2 crystal grains do not extend to the main surface of the second layer on a side opposite to a first layer side.