Acoustic Wave Electrode Layout With Through-Holes for Crack Relief
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Solution Overview
Problem
Acoustic wave devices with air gaps between support substrates and piezoelectric layers are prone to cracks in the piezoelectric layer, which can lead to reduced performance and reliability.
Innovation Solution
The design incorporates a support substrate with an air gap and a piezoelectric layer featuring through-holes and interdigitated electrode fingers that overlap the air gap, allowing for stress alleviation and preventing cracks by ensuring the piezoelectric layer is not fixed to the substrate, thereby reducing the likelihood of cracking.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If the piezoelectric layer is fixed to the support substrate, then structural stability is improved, but cracks occur in the piezoelectric layer due to stress concentration
Solution Approach 1:
The support substrate is segmented into regions with air gaps that divide the piezoelectric layer into separate supported regions. This segmentation allows different parts of the piezoelectric layer to move independently, reducing stress concentration and preventing cracks while maintaining overall structural stability.
Solution Approach 2:
Air gaps are introduced as intermediary spaces between the piezoelectric layer and support substrate. These air gaps act as stress-relief zones that decouple the piezoelectric layer from the rigid substrate, allowing thermal expansion and mechanical stress without causing cracks.
2Volume of moving object
If the number of electrode pairs is reduced for size minimization, then device size is reduced, but resonance characteristics and coupling coefficients may deteriorate
Solution Approach 1:
The air gaps are strategically positioned in specific local regions beneath the piezoelectric layer to create stress-relief zones without affecting the overall electrode structure. This localized modification allows size reduction while preserving the resonance characteristics and coupling coefficients in the functional electrode regions.
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 reduces or prevents cracks in the piezoelectric layer, maintaining the structural integrity and performance of the acoustic wave device, even when the number of electrode pairs is reduced for size minimization, while maintaining good resonance characteristics and high coupling coefficients.
Implementation Method 1
a piezoelectric layer provided in a first direction of the support
Data Source
AI summary
An acoustic wave device includes a support with a thickness in a first direction, a piezoelectric layer provided in the first direction of the support, first electrode fingers provided in the first direction of the piezoelectric layer and extending in a second direction orthogonal to the first direction, and second electrode fingers facing any of the first electrode fingers in a third direction orthogonal to the first and second directions and extending in the second direction. A through-hole extends through the piezoelectric layer in the first direction. The electrode fingers and the through-hole at least partially overlap an air gap in the support in plan view in the first direction. At least one of the electrode fingers is provided in the second direction of the through-hole. The electrode fingers are not provided in the third direction of the through-hole.