Co-Packaged BAW Filters With Shared Trimming for Smaller RF Modules
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Solution Overview
Problem
The increasing demand for miniature, low-loss, and low-temperature-drift radio frequency (RF) filters in crowded mobile communication frequency spectra poses challenges in achieving desirable filter performance while reducing size and cost effectively, particularly for bulk acoustic wave (BAW) filters.
Innovation Solution
The solution involves co-packaging multiple BAW filters on a single die, sharing a common material stack and trimming steps to achieve overlapping passbands and resonant frequencies, reducing the number of trimming steps and mask costs, and allowing for flexible and complex designs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If multiple BAW filters are packaged separately, then each filter can be optimized independently, but the overall module size increases and fabrication costs increase
Solution Approach 1:
The patent combines multiple BAW filters onto a single die, integrating first and second filters with overlapping passbands in close proximity. This merging approach reduces the overall module size by eliminating separate packaging requirements while maintaining independent filter functionality through shared substrate and selective electrical connections.
Solution Approach 2:
The patent implements a universal material stack that serves multiple filter functions simultaneously. The common substrate and shared material layers support both first and second BAW filters with different passband characteristics, allowing a single structure to perform multiple filtering functions across overlapping frequency ranges.
2Manufacturing precision
If multiple separate trimming steps are performed for each filter, then each filter achieves precise frequency control, but fabrication time and mask costs increase
Solution Approach 1:
The patent merges trimming operations by performing selective trimming on shared material stacks that affect multiple filters. A single trimming step can adjust the resonant frequencies of both first and second BAW filters simultaneously by removing material from common layers, thereby achieving precise frequency control while reducing the total number of trimming steps required.
Solution Approach 2:
The patent applies preliminary trimming to shared material stacks before final filter assembly, establishing baseline frequency characteristics that can be fine-tuned later. This preliminary action on common structures enables subsequent precise frequency adjustments with fewer steps, as the foundational frequency alignment is already established.
3Adaptability or versatility
If filters use different material stacks, then each filter can be optimized for its specific frequency range, but fabrication complexity and cost increase
Solution Approach 1:
The patent employs a universal material stack comprising common layers that support multiple BAW filters with different passband requirements. The shared substrate and material layers are designed to accommodate both first and second filters, enabling a single fabrication process to produce filters across different frequency ranges without requiring separate material deposition sequences.
Solution Approach 2:
While using a universal material stack, the patent applies local quality variations through selective trimming and regional material modifications. Specific areas of the shared material stack are selectively removed or modified to tune individual filter characteristics, allowing each filter to be optimized for its specific frequency range while maintaining overall manufacturing simplicity through the common base structure.
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 approach enables reduced module sizes, lower fabrication costs, and improved filter performance by leveraging shared processing steps and material stacks, while maintaining or improving frequency selectivity and stability.
Implementation Method 1
In BAW filters, acoustic waves propagate in a bulk of a piezoelectric layer
Implementation Method 2
A SAW filter can include an interdigital transductor electrode on a piezoelectric substrate and can generate a surface acoustic wave on a surface of the piezoelectric layer
Data Source
AI summary
Bulk acoustic wave resonators of two or more different filters can be on a common die. The two filters can be included in a multiplexer, such as a duplexer, or implemented as standalone filters. With bulk acoustic wave resonators of two or more filters on the same die, the filters can be implemented in less physical space compared to implementing the same filters of different die. Related methods, radio frequency systems, radio frequency modules, and wireless communication devices are also disclosed.