Composite Electrode Acoustic Wave Structure for Bending Control
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Acoustic wave devices experience excessive bending of the piezoelectric layer due to differences in linear expansion coefficients between the busbar electrode and the piezoelectric layer, leading to deteriorated characteristics.
Innovation Solution
Incorporating a support structure with a space overlapping the functional electrodes, where the electrodes consist of a first metal layer and a second metal layer with a smaller linear expansion coefficient, to reduce or prevent excessive bending of the piezoelectric layer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single-layer busbar electrode is used, then the device structure is simple, but excessive bending of the piezoelectric layer occurs due to large linear expansion coefficient difference
Solution Approach 1:
The busbar electrode is constructed as a composite structure with a first metal layer (Al or Al alloy) and a second metal layer (Cu, Au, Ag, or their alloys) with different linear expansion coefficients. This composite configuration balances the thermal expansion characteristics, reducing the overall expansion coefficient difference with the piezoelectric layer and preventing excessive bending while maintaining structural simplicity.
2Reliability
If the linear expansion coefficient of the electrode is reduced, then piezoelectric layer bending is prevented, but the electrode material selection becomes more restricted
Solution Approach 1:
By combining metals with different linear expansion coefficients in a layered structure, the invention achieves an effective intermediate expansion coefficient that matches the piezoelectric layer better. The first metal layer provides structural foundation while the second metal layer adjusts the overall expansion characteristics, offering versatile material selection possibilities.
Solution Approach 2:
The invention changes the linear expansion coefficient parameter of the electrode by selecting specific metal combinations and thickness ratios. By adjusting the thickness of each layer, the effective linear expansion coefficient can be tuned to match different piezoelectric materials, providing adaptability across various device configurations.
3Volume of moving object
If the device is miniaturized, then the Q-value reduction is significant, but larger device size maintains performance
Solution Approach 1:
The composite electrode structure reduces piezoelectric layer bending and associated energy losses, allowing the device to maintain high Q-values even at miniaturized dimensions. By preventing excessive bending, the composite structure preserves the mechanical integrity and acoustic performance necessary for high Q-values in smaller devices.
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 effectively minimizes excessive bending of the piezoelectric layer, maintaining the device's performance and resonance characteristics while allowing for miniaturization without significant Q-value reduction.
Implementation Method 1
a linear expansion coefficient of the second metal layer is smaller than a linear expansion coefficient of the first metal layer
Data Source
AI summary
An acoustic wave device includes a support including a support substrate, a piezoelectric layer on the support substrate, a space overlapping at least a portion of the piezoelectric layer, and a functional electrode on the piezoelectric layer. The support includes a space at a position at least partially overlapping the functional electrode in plan view. The functional electrode includes a first metal layer and a second metal layer on at least a portion of the first metal layer. A linear expansion coefficient of the second metal layer is smaller than a linear expansion coefficient of the first metal layer.