Composite Substrate Waviness Control for SAW Filter Q-Value
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Solution Overview
Problem
The performance of Surface Acoustic Wave (SAW) filters in communication devices has not kept pace with increasing communication traffic, necessitating an improvement in the composite substrates used in these filters.
Innovation Solution
A composite substrate is developed with a support substrate and a piezoelectric layer, where the amplitude of waviness with a spatial frequency greater than 0.045 cyc/mm is 10 nm or less, and the thickness difference between two points on the piezoelectric layer is 100 nm or less, with the piezoelectric layer being 5 μm or less in thickness, to enhance the performance of SAW filters.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional composite substrates are used in SAW filters, then the basic filtering function is achieved, but the performance cannot keep pace with increasing communication traffic
Solution Approach 1:
The patent applies parameter changes by precisely controlling the waviness amplitude (≤10 nm) and spatial frequency (>0.045 cyc/mm) of the support substrate, and the piezoelectric layer thickness (≤5 μm with ≤100 nm variation). These parameter optimizations enable the SAW filter to handle higher communication traffic while maintaining reliability.
2Reliability
If the piezoelectric layer thickness is reduced to improve performance, then Q-value and temperature characteristics improve, but manufacturing precision requirements increase
Solution Approach 1:
The patent applies preliminary action by pre-forming the support substrate with controlled waviness parameters before depositing the piezoelectric layer. This preliminary preparation ensures that when the thin piezoelectric layer (≤5 μm) is formed, it inherits the substrate's precision, achieving both high Q-value and acceptable manufacturing precision.
Solution Approach 2:
The patent controls the piezoelectric layer thickness parameter to be ≤5 μm with a maximum variation of 100 nm between different points. This precise parameter control enables improved Q-value and temperature characteristics while maintaining manufacturability through standardized precision requirements.
3Manufacturing precision
If the waviness amplitude of the support substrate is reduced to improve thickness accuracy, then manufacturing complexity increases
Solution Approach 1:
The patent specifies precise parameter ranges for the support substrate waviness: amplitude ≤10 nm and spatial frequency >0.045 cyc/mm. By defining these specific parameter boundaries, the patent achieves high thickness accuracy without requiring overly complex substrate shapes, as long as the waviness remains within the specified parameter limits.
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 composite substrate improves the performance of SAW filters by achieving high thickness accuracy and reducing characteristic variations, leading to improved Q-value and temperature characteristics of the surface acoustic wave elements.
Implementation Method 1
a composite substrate having a piezoelectric layer
Implementation Method 2
a filter utilizing a surface acoustic wave (SAW filter) has been used
Data Source
AI summary
A composite substrate according to includes: a support substrate; and a piezoelectric layer arranged on one side of the support substrate, wherein an amplitude of a waviness having a spatial frequency of more than 0.045 cyc/mm according to a shape of the support substrate is 10 nm or less.