Elastic Wave Device Through-Electrode Stability
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Solution Overview
Problem
Conventional elastic wave devices using plate waves face significant changes in characteristics due to variations in the thickness of the piezoelectric substrate or electrode, leading to unstable manufacturing and increased loss in high-frequency bands.
Innovation Solution
An elastic wave device with a piezoelectric substrate of LiNbO3 and an IDT electrode made from metals like Al, Cu, W, Au, Pt, Ta, or Ni, where the IDT electrode passes through the substrate, maintaining consistent fractional bandwidth and acoustic velocity even with changes in thickness, and having a duty of 0.5 or less.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the thickness of the piezoelectric substrate or electrode is reduced to achieve wide bandwidth, then the fractional bandwidth increases, but the resistance loss of the electrode increases significantly in high frequency bands
Solution Approach 1:
The patent changes the geometric parameters of the IDT electrode, specifically setting the duty ratio to 0.5 or less and optimizing the electrode thickness to be 0.05λ to 0.2λ. This parameter optimization allows achieving wide bandwidth characteristics while maintaining low resistance loss by finding the optimal balance point between these two competing requirements.
Solution Approach 2:
The patent employs composite material structures by combining the piezoelectric substrate with the metal electrode layer, where the electrode material is selected from metals with low resistivity such as Al, Cu, W, Au, Pt, Ta, Mo, or Ni. This composite structure optimizes both the electromechanical coupling for bandwidth and the electrical conductivity for reducing resistance loss.
2Adaptability or versatility
If the thickness of the piezoelectric substrate or electrode is varied to optimize performance, then the bandwidth may improve, but the characteristics (acoustic velocity, stop band) change significantly making stable manufacture difficult
Solution Approach 1:
The patent establishes specific parameter ranges that are optimized to provide both wide bandwidth and stable characteristics: duty ratio of 0.5 or less, electrode thickness of 0.05λ to 0.2λ, and piezoelectric substrate thickness of 0.01λ to 0.1λ. These parameter specifications create a manufacturing window where characteristics remain stable while achieving the desired bandwidth 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 stabilizes the fractional bandwidth and acoustic velocity, reducing resonant resistance and loss, facilitating the manufacture of devices with desired characteristics and widening manufacturing tolerances.
Implementation Method 1
an elastic wave device includes a piezoelectric substrate having a thickness equal to or less than a wavelength of a propagating elastic wave, and an IDT electrode
Data Source
AI summary
An elastic wave device includes a piezoelectric substrate and an interdigital transducer electrode disposed in a piezoelectric vibrating portion of the piezoelectric substrate to pass through the piezoelectric substrate.