Acoustic Wave Membrane Electrode Layout for Crack-Resistant Boundaries
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Solution Overview
Problem
Acoustic wave devices with piezoelectric layers experience cracks due to stress concentration at the boundary between supported and unsupported portions, leading to potential failure.
Innovation Solution
Incorporating a cavity portion in the support structure to create a membrane and supported portion in the piezoelectric layer, with boundary covering electrodes over the entire boundary to distribute stress evenly.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a through-hole is provided in the support body and the piezoelectric layer covers the through-hole, then the acoustic wave device can be manufactured, but stress concentrates at the boundary between supported and unsupported portions causing cracks
Solution Approach 1:
The invention applies a boundary covering electrode specifically at the boundary region between the membrane portion and supported portion of the piezoelectric layer. This localized structural modification provides additional mechanical support and stress distribution precisely where stress concentration occurs, without affecting other regions of the device. The boundary covering electrode has different properties from the functional electrodes, creating local quality enhancement at the critical boundary zone.
2Adaptability or versatility
If the piezoelectric layer is provided over the cavity portion to enable functional electrode operation, then acoustic wave functionality is achieved, but the boundary region becomes vulnerable to stress concentration
Solution Approach 1:
The boundary covering electrode is formed in advance during the manufacturing process, before the device undergoes operational stress. This preliminary structural reinforcement is integrated into the fabrication sequence, ensuring that the boundary region is strengthened before any stress concentration or crack formation can occur during device operation.
Solution Approach 2:
The boundary covering electrode acts as an intermediary structural element between the membrane portion and supported portion of the piezoelectric layer. It provides a transition zone that mediates the stress distribution between these two regions, preventing direct stress concentration at the sharp boundary and reducing the likelihood of crack initiation.
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
Prevents cracks in the piezoelectric layer by distributing stress uniformly, enhancing the device's reliability and longevity.
Implementation Method 1
a piezoelectric layer is provided on a support body. A pair of electrodes are provided on the piezoelectric layer. By applying an AC voltage to a gap between the above electrodes, a bulk wave in a thickness-shear mode is excited.
Data Source
AI summary
An acoustic wave device includes a support including a support substrate, a piezoelectric layer on the support, and a functional electrode on the piezoelectric layer and including at least one pair of electrodes. The support includes a cavity portion overlapping at least a portion of the functional electrode in plan view. The piezoelectric layer includes a membrane portion overlapping the cavity portion in plan view, and a supported portion supported by the support. A boundary covering electrode is provided on the piezoelectric layer over an entire or substantially an entire portion overlapping a boundary between the membrane portion and the supported portion in plan view.