BAW Package Structure With Integrated Passives for Compact MMICs
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Solution Overview
Problem
Conventional BAW filter packaging processes are complex, requiring multiple steps and resulting in larger package sizes due to the use of two wafers and metal formation processes, which complicates integration into Monolithic Microwave Integrated Circuits (MMICs).
Innovation Solution
A BAW package structure is fabricated separately and then coupled to the BAW filter, using photosensitive polymer for the wall and roof layers, and passive elements like capacitors and inductors are integrated into the package structure, eliminating the need for mounting them on the BAW filter or PCB, thereby simplifying the process and reducing size.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If wafer bonding with metal material is used to protect BAW filter, then the BAW filter is protected from external environment, but the package size and thickness increase due to two wafers and large bonding layer area
Solution Approach 1:
The patent merges the protective cap and the BAW filter into a single integrated structure. The cap is formed by extending the substrate laterally to surround the resonator portion, eliminating the need for separate wafer bonding. This integration reduces the overall package size while maintaining protection of the BAW filter from external environment.
Solution Approach 2:
The patent extracts the metal bonding layer and redistribution layer formation processes from the packaging procedure. By using a laterally extended substrate instead of metal bonding, the complex metal formation steps are removed, simplifying the manufacturing process and reducing package complexity.
2Reliability
If wafer bonding with metal material is used to protect BAW filter, then the BAW filter is protected from external environment, but the manufacturing process becomes more complex due to metal formation and silicon via layer formation
Solution Approach 1:
The patent removes the metal bonding layer and silicon via layer formation steps from the manufacturing process. The protective cap is formed by simple lateral extension of the substrate, eliminating the need for complex metal deposition, patterning, and via formation processes required in conventional wafer bonding methods.
3Reliability
If BAW filter is manufactured with conventional wafer bonding, then protection is achieved, but integration into MMIC is difficult due to increased size and process complexity
Solution Approach 1:
The patent merges the BAW filter and protective cap into a single integrated structure that can be directly mounted on MMIC substrates. The laterally extended substrate forms both the protective enclosure and the mounting interface, enabling seamless integration into MMIC assemblies while maintaining compatibility with standard mounting procedures.
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 simplifies the manufacturing process and allows for the formation of a thinner and smaller BAW package, suitable for MMIC applications, by integrating passive elements within the package structure.
Implementation Method 1
a piezoelectric layer formed above the lower electrode... causes resonance due to the piezoelectric properties
Implementation Method 2
using photosensitive polymer for the wall and roof layers
Data Source
AI summary
A bulk acoustic wave (BAW) package according to an embodiment of the present disclosure comprises a BAW filter including a substrate having at least one cavity on an upper surface thereof, a lower electrode formed above the substrate, a piezoelectric layer formed above the lower electrode, and an upper electrode formed above the piezoelectric layer; and a package structure formed above the BAW filter to protect the BAW filter, wherein the package structure comprises a roof layer including a passive element and a wall layer extending vertically along edges of the roof layer.