Hybrid Acoustic Wave Filter Layout for Shorter LC Paths
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Solution Overview
Problem
Conventional BAW filters face issues with long conductive paths and space utilization, limiting frequency tuning and increasing substrate size, due to the inclusion of SMT capacitors and inductors.
Innovation Solution
A compact hybrid acoustic wave filter structure is designed with a multi-layer metallization structure, pillar structures, and an acoustic unit (AU) that includes a metal-insulation-metal capacitor and inductor, reducing path lengths and substrate space by integrating these components within the metallization layers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If conventional surface mount technology (SMT) capacitors and inductors are used with long conductive paths, then the BAW filter can be assembled, but the device occupies valuable space and cannot effectively shape or tune the BAW response
Solution Approach 1:
The patent merges the capacitor and inductor components directly into the metallization structure of the substrate, eliminating the need for separate SMT components. The first metallization structure includes a capacitor portion and inductor portion that are integrated into the same substrate layer, reducing the overall device footprint while maintaining assembly capability.
Solution Approach 2:
The patent transitions from planar SMT component placement to three-dimensional vertical stacking, where the acoustic unit is positioned above the substrate and connected through vertical metallization paths. This dimensional change allows components to be arranged in the Z-direction rather than consuming horizontal substrate area.
2Ease of manufacture
If conventional SMT components with long conductive paths are used, then the BAW filter can be assembled, but the response shaping and tuning capability is lost
Solution Approach 1:
The integration of the capacitor and inductor into the metallization structure creates direct electrical connections between the acoustic unit and the LC components, eliminating long conductive paths. This merging enables effective response shaping and tuning by placing the tuning components immediately adjacent to the acoustic resonator.
3Ease of manufacture
If the acoustic unit is positioned far from the LC components, then assembly is simplified, but the conductive paths become excessively long
Solution Approach 1:
The capacitor and inductor are merged into the substrate's metallization structure, placing them in immediate proximity to the acoustic unit. This integration minimizes the conductive path length to virtually zero, as the electrical connections are made through the same metallization layers that form the component structures themselves.
4Device complexity
If separate SMT components are used, then the design is straightforward, but the overall device size increases
Solution Approach 1:
The patent combines multiple discrete functions (substrate, capacitor, inductor, and mounting structure) into a single integrated metallization structure. This merging eliminates the need for separate SMT components and their associated packaging, significantly reducing the device footprint while maintaining design simplicity through a unified structure.
Solution Approach 2:
The capacitor and inductor are nested within the substrate's metallization layers, with the acoustic unit positioned above and connected through vertical vias. This nesting arrangement allows multiple components to occupy the same horizontal footprint by utilizing the vertical dimension, effectively reducing the overall device volume.
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 new design achieves a 30% reduction in size, 1.5-2.0 dB performance improvement, and 10-20% thermal performance enhancement, along with a 20% reduction in assembly costs, while enabling effective frequency shaping.
Implementation Method 1
the capacitor comprises a metal-insulation-metal (MIM) capacitor
Implementation Method 2
the inductor is comprised of a second portion of the first metallization structure
Implementation Method 3
Surface acoustic wave (SAW) and bulk acoustic wave (BAW) filters are devices which make use of the properties of piezoelectric material to convert electrical signals to acoustic waves and back to electrical signals
Data Source
AI summary
A compact, hybrid, acoustic wave filter structure is disclosed. In an aspect an apparatus comprises a substrate; a first, multi-layer metallization structure disposed above the substrate; a plurality of pillar structures disposed above, and electrically coupled to, the first metallization structure; a second metallization structure disposed above, an electrically coupled to, the plurality of pillar structures. An acoustic unit (AU) is disposed between the first and second metallization structures and adjacent to at least one of the pillar structures. The AU comprises a surface acoustic wave or bulk acoustic wave acoustic resonator that is electrically coupled to a capacitor and an inductor. The capacitor comprises a metal-insulation-metal capacitor that is formed from a portion of the first metallization structure and optionally also from at least one pillar structure and a portion of the second metallization structure. The inductor is comprised of a second portion of the first metallization structure.