SAW Composite Substrate Reflective Layer for Heat-Resistant Wave Confinement
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Solution Overview
Problem
Existing composite substrates for surface acoustic wave (SAW) filters face challenges in maintaining heat resistance while effectively confining elastic wave energy within the piezoelectric layer.
Innovation Solution
A composite substrate is designed with a piezoelectric layer and a reflective layer that includes a high-impedance layer and a low-impedance layer, specifically containing silicon oxide, with a high-impedance layer structure comprising more than 70% columnar or granular structures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a composite substrate with a reflective layer is used to confine elastic wave energy in the piezoelectric layer, then the confinement of elastic wave energy is improved, but the heat resistance during thermal processing deteriorates
Solution Approach 1:
The patent changes the structural parameters of the high-impedance layer by controlling the ratio of first structures (columnar or granular) to be more than 70% of the total area. This parameter change optimizes both the elastic wave confinement capability and the heat resistance, resolving the technical contradiction between these two requirements.
Solution Approach 2:
The reflective layer is constructed as a composite structure with high-impedance layers and low-impedance layers (silicon oxide). This composite material structure enables simultaneous achievement of elastic wave energy confinement and improved heat resistance during thermal processing.
2Temperature
If the high-impedance layer contains a high ratio of first structures (columnar or granular), then the heat resistance is improved, but the manufacturing precision of the layer structure deteriorates
Solution Approach 1:
The patent specifies that the ratio of first structures in the high-impedance layer should be more than 70% of the total area. This parameter range was determined to provide optimal balance between heat resistance and manufacturing feasibility, allowing sufficient thermal stability while remaining achievable with conventional manufacturing processes.
3Device complexity
If the thickness of the high-impedance layer and low-impedance layer is reduced to 0.01 μm to 1 μm, then the device complexity is reduced, but the reliability of elastic wave confinement deteriorates
Solution Approach 1:
The patent determines the optimal thickness range of 0.01 μm to 1 μm for both high-impedance and low-impedance layers. This parameter optimization ensures that the layers are thin enough to reduce device complexity and manufacturing difficulty, while still maintaining sufficient elastic wave confinement capability through the optimized first structure ratio.
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 proposed composite substrate achieves excellent heat resistance and effective confinement of elastic wave energy, reducing the occurrence of peeling and cracking during thermal processing.
Implementation Method 1
the reflective layer includes a high-impedance layer and a low-impedance layer containing silicon oxide
Implementation Method 2
a piezoelectric layer
Data Source
AI summary
A composite substrate includes: a piezoelectric layer; and a reflective layer arranged on a rear surface side of the piezoelectric layer, wherein the reflective layer includes a high-impedance layer and a low-impedance layer containing silicon oxide, and wherein a ratio of a region of first structures in the high-impedance layer is more than 70%.