Integrated RF Filter Layout Protecting the Acoustic Dome
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Solution Overview
Problem
Conventional RF filters using surface mounted device (SMD) inductors face issues such as physical dimension limitations, cost, and performance degradation due to manufacturing variations, which lead to space constraints and acoustic dome damage during fabrication.
Innovation Solution
The integration of 3D solenoid inductors within RF filters using a lower mold that encapsulates the acoustic dome, allowing for electrical coupling with bond pads through conductive pillars and redistribution layers, while protecting the acoustic dome and enhancing filter performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If SMD inductors are used in RF filters, then the filter can be assembled, but the physical dimensions increase and space efficiency decreases
Solution Approach 1:
The patent merges the inductor and acoustic die into a single integrated structure where the inductor is formed directly on the acoustic die using the same fabrication process. This eliminates the need for separate SMD inductor components and their associated assembly steps, thereby improving space efficiency while reducing assembly complexity
Solution Approach 2:
The patent transitions from using discrete SMD inductors (three-dimensional components requiring vertical stacking) to forming planar inductors directly on the acoustic die surface. This two-dimensional integration approach improves space efficiency by utilizing the substrate plane rather than requiring additional vertical space for separate components
2Manufacturing precision
If SMD inductors are used in RF filters, then the filter can be manufactured, but manufacturing variations increase and performance degrades
Solution Approach 1:
The patent combines the inductor fabrication with the acoustic die manufacturing process, using the same deposition and patterning steps for both components. This unified approach eliminates variability introduced by separate assembly processes, improving performance consistency while the process integration actually simplifies the overall manufacturing workflow
Solution Approach 2:
The patent changes the manufacturing parameters from discrete component assembly (handling, placement, reflow) to direct deposition and patterning processes. This parameter change from mechanical assembly to material deposition improves manufacturing precision by eliminating assembly-related variations while maintaining process simplicity through standard semiconductor fabrication techniques
3Reliability
If the acoustic dome is exposed for inductor connection, then electrical coupling is achieved, but acoustic integrity is compromised
Solution Approach 1:
The patent segments the acoustic die into distinct functional regions: the acoustic dome area that remains covered and protected, and the peripheral areas where inductors are formed and electrical connections are made. This spatial segmentation allows the acoustic dome to maintain its integrity while still enabling electrical coupling through separately formed connection structures
Solution Approach 2:
The patent introduces an intermediary connection structure (such as a connection pad or via) that provides electrical coupling between the inductor and the acoustic die without requiring direct exposure of the acoustic dome. This intermediary element mediates between the electrical connection requirement and the acoustic integrity requirement, allowing both to be satisfied simultaneously
Data Source
AI summary
Disclosed is a radio frequency (RF) filter that vertically integrates an acoustic die with inductors formed in one or more layers above the acoustic die. The acoustic die may be over-molded so that the acoustic dome, important for maintaining acoustic integrity, may be protected.