SAW Filter Package Structure for Suppressing Cavity Bending
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Solution Overview
Problem
Existing acoustic wave filters face challenges in achieving low insertion loss across the entire passband, and conventional designs are prone to cavity bending and instability due to heat or stress during production, affecting filter performance.
Innovation Solution
The implementation of a surface acoustic wave (SAW) filter package with trenches and a cavity forming layer, optionally with a resin layer, and the use of temperature compensation layers to stabilize the structure and reduce bending, combined with a multiplexer design incorporating series TCSAW resonators and shunt BAW resonators for improved insertion loss.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional acoustic wave filter designs are used, then the structure is simple, but cavity bending occurs due to heat or stress during production, affecting filter performance
Solution Approach 1:
The cavity forming layer is divided into multiple segments separated by trenches, with each segment independently supporting a filter. This segmentation prevents stress propagation across the entire cavity, reducing bending and improving structural stability during production.
Solution Approach 2:
The cavity forming layer is constructed using composite materials with different thermal expansion coefficients and mechanical properties to compensate for stress and heat-induced deformation, thereby suppressing cavity bending and maintaining filter performance stability.
2Loss of energy
If conventional designs without trenches are used, then manufacturing is easier, but insertion loss across the entire passband cannot be sufficiently reduced
Solution Approach 1:
The introduction of trenches segments the cavity forming layer, enabling better control over acoustic wave propagation and reducing energy loss. The segmented structure allows for optimized filter design in each section, achieving lower insertion loss across the entire passband.
Solution Approach 2:
Different regions of the cavity forming layer are designed with locally optimized properties, such as varying thickness or material composition in different sections, to minimize insertion loss at specific frequency bands while maintaining overall structure functionality.
3Area of stationary object
If the cavity forming layer extends across the entire substrate, then coverage is maximized, but bending increases under heat or stress
Solution Approach 1:
The continuous cavity forming layer is segmented into discrete sections by trenches, allowing each section to independently accommodate thermal expansion and stress without causing bending across the entire structure. This maintains full substrate coverage while improving bending resistance.
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 design enhances stability and uniformity during production, maintaining filter performance by reducing cavity bending and achieving better low channel insertion loss and overall insertion loss compared to conventional designs.
Implementation Method 1
a SAW filter formed in each trench of the one or more trenches... and a cavity forming layer extending horizontally across the substrate and each trench
Implementation Method 2
A surface acoustic wave resonator can include an interdigital transductor (IDT) electrode on a piezoelectric substrate. The surface acoustic wave resonator can generate a surface acoustic wave on a surface of the piezoelectric layer
Data Source
AI summary
A surface acoustic wave (SAW) filter package comprises a substrate, one or more trenches formed in the substrate, a SAW filter formed in each trench of the one or more trenches, and a cavity forming layer extending horizontally across the substrate and each trench.