Single-Substrate Acoustic Multiplexer for Heat-Stable SAW Filtering
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Solution Overview
Problem
Current multiplexers with discrete electroacoustic components are prone to thermal mismatch issues, poor heat dissipation, and difficulty in optimizing multiple filter functions on a single chip, leading to increased size, material losses, and sensitivity to cracks and failure.
Innovation Solution
A monolithic multiplexer with a single Si carrier substrate, thin film piezoelectric layer, and dielectric layers, featuring SAW filter circuits connected in parallel, and a package design that allows for effective heat dissipation and flexible resonator placement, using materials with high thermal conductivity to minimize thermal resistance and spurious modes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If multiple filter functions are combined on a single chip, then device size is reduced and space consumption decreases, but the chip becomes more sensitive to cracks and failure due to thermal mismatch
Solution Approach 1:
The patent combines multiple filter functions (at least three acoustic filters) onto a single chip substrate, integrating what would traditionally be separate discrete components. This merging reduces the overall device volume and eliminates the need for a large carrier board, while the unified thermal field reduces thermal mismatch issues that plague multi-chip assemblies.
Solution Approach 2:
The patent changes the thermal and mechanical parameters of the substrate by selecting materials with specific properties (such as ceramic substrates with high thermal conductivity and matched thermal expansion coefficients). This parameter optimization allows the single chip to handle multiple filter functions without excessive thermal stress or mechanical failure.
2Manufacturing precision
If discrete filter chips are used on a carrier board, then each filter function can be separately optimized, but the carrier board must be large enough to maintain minimum distances, increasing device size
Solution Approach 1:
Instead of using separate filter chips on a carrier board, the patent merges multiple filter functions into a single integrated chip structure. This eliminates the need for a large carrier board and maintains all necessary minimum distances within the unified chip design, significantly reducing the overall device area.
Solution Approach 2:
The single chip is designed to perform multiple filter functions simultaneously, with each filter circuit independently optimized for its specific frequency band. The universal chip structure accommodates different filter technologies and optimized layer stacks for each function without requiring separate physical chips.
3Strength
If discrete filter chips are used, then individual chip size remains small for mechanical stability, but heat dissipation is not optimal and material losses increase during wafer dicing
Solution Approach 1:
The patent merges multiple filter functions into a single chip, creating a larger thermal mass that improves heat dissipation efficiency. The unified thermal field allows heat generated by multiple active filters to be distributed and dissipated more effectively than in discrete chip configurations, reducing overall energy loss.
Solution Approach 2:
The patent optimizes the chip size and thermal parameters to achieve both mechanical stability and efficient heat dissipation. By carefully controlling the chip dimensions, substrate material properties, and thermal conductivity, the design achieves a balance where the chip is large enough for effective heat dissipation but maintains adequate mechanical strength.
4Volume of moving object
If a single chip with multiple filter functions is used, then device size is reduced, but optimization of different filter functions is difficult to meet simultaneously
Solution Approach 1:
The patent applies local quality by allowing different regions of the single chip to have different optimized structures and materials tailored to specific filter functions. Each filter circuit can have its own optimized layer stack and acoustic resonator design, enabling simultaneous optimization of multiple filter functions while maintaining a compact single-chip form factor.
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 solution reduces material losses, improves heat dissipation, and enhances mechanical stability, allowing for precise frequency trimming and reduced size, while maintaining sufficient isolation between frequency bands without crosstalk.
Implementation Method 1
a thin film piezoelectric layer above the substrate
Implementation Method 2
uses materials with high thermal conductivity to minimize thermal resistance
Implementation Method 3
three SAW filter circuits... Each of the filter circuits comprises a series signal line and a number of SAW resonators
Data Source
AI summary
At least three acoustic filters circuits FC are arranged on a single chip CH. At least two of them are electrically connected already on the chip for multiplexing. This reduces space consumption and leads to smaller device size.