Boundary Acoustic Wave Layout for Thin Multi-Element Integration
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Solution Overview
Problem
Boundary acoustic wave devices face challenges in achieving a small mounting space and thickness suitable for thin apparatuses while maintaining effective frequency characteristics, as existing devices often require complex packaging and are unsuitable for thin applications due to their large thickness.
Innovation Solution
A boundary acoustic wave device is designed with a substrate and dielectric films where the substrate's slow transverse wave velocity is greater than the dielectric films', and optionally includes recessed or projecting portions and sound-absorbing films to prevent spurious modes, allowing for integration of multiple elements on a single chip and reducing manufacturing costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If boundary acoustic wave elements are laminated in the thickness direction to reduce mounting space, then the mounting space is reduced, but the device thickness increases making it unsuitable for thin apparatuses
Solution Approach 1:
The patent transitions from three-dimensional lamination (stacking elements in the thickness direction) to two-dimensional planar integration (arranging elements on the same substrate plane). This dimensional change allows multiple boundary acoustic wave elements to be mounted in parallel on a single substrate without increasing device thickness, thereby reducing both mounting space and maintaining thin profile suitable for portable apparatuses.
2Reliability
If surface acoustic wave devices use cavities on piezoelectric substrates, then acoustic wave propagation is enabled, but the package structure becomes complicated and device size increases
Solution Approach 1:
The patent extracts and eliminates the cavity structure from the device design by utilizing the substrate surface itself for acoustic wave propagation. Instead of requiring three-dimensional cavities, the invention uses surface acoustic waves that propagate along the substrate surface, thereby simplifying the package structure while maintaining acoustic wave propagation functionality.
Solution Approach 2:
The patent replaces the mechanical cavity structure with a surface-based acoustic wave propagation system. By using surface acoustic waves that travel along the substrate surface rather than requiring physical cavities, the invention substitutes a complex mechanical packaging structure with a simpler surface-wave-based system.
3Ease of manufacture
If multiple boundary acoustic wave elements are integrated on one chip, then manufacturing cost is reduced, but spurious modes may occur affecting frequency characteristics
Solution Approach 1:
The patent introduces acoustic absorption films as intermediary elements between adjacent boundary acoustic wave elements. These absorption films act as acoustic isolators that prevent spurious mode coupling between neighboring elements, thereby maintaining frequency characteristics while allowing multiple elements to be integrated on a single substrate for cost-effective manufacturing.
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
The solution enables a compact, low-cost boundary acoustic wave device with improved frequency characteristics by preventing unwanted spurious modes and allowing for efficient manufacturing, making it suitable for thin applications.
Implementation Method 1
Either the substrate or the first and second dielectric films have piezoelectric characteristics
Implementation Method 2
boundary acoustic waves propagating along a boundary surface between different media
Data Source
AI summary
A boundary acoustic wave device has a small thickness, which is suitable for thin apparatuses, and can be manufactured at low cost. The boundary acoustic wave device includes a first IDT electrode disposed on a first surface of a substrate, a first insulating film covering the first IDT electrode, a second IDT electrode disposed on a second surface of the substrate, and a second insulating film covering the second IDT electrode. Either the substrate or the first and second insulating films have piezoelectric characteristics.