Wafer Level SAW Device Packaging with Tapered Viahole
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Solution Overview
Problem
Conventional SAW device packaging methods limit miniaturization and increase manufacturing costs due to the size and complexity of the SAW filter, as the SAW element becomes smaller, making it difficult to achieve compact and high-efficient packaging.
Innovation Solution
A SAW device wafer level package with a cap wafer bonded to the SAW device, featuring a viahole with a first via portion of gradually smaller diameter and a second via portion of gradually greater diameter, filled with a conductive member, including a first metal layer covering the viahole and a second metal layer electroplated to connect with the cap pad, allowing for a more compact and efficient packaging structure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If conventional SAW device packaging methods are used, then the SAW element can be hermetically sealed, but the package size becomes large and manufacturing complexity increases
Solution Approach 1:
The packaging structure is divided into a device wafer and a cap wafer that are separately fabricated and then bonded together. This segmentation allows for simplified manufacturing of each component and reduces overall package complexity while maintaining hermetic sealing.
Solution Approach 2:
The device wafer and cap wafer are merged through bonding to form a compact integrated package. This combining approach eliminates the need for separate packaging components and complex assembly processes, reducing both size and manufacturing complexity.
2Volume of moving object
If the SAW element size is reduced for miniaturization, then compactness is improved, but manufacturing becomes more complicated and costs increase
Solution Approach 1:
The SAW element is fabricated on the device wafer before bonding to the cap wafer. This preliminary fabrication allows for precise control of small SAW elements using standard semiconductor manufacturing techniques, making miniaturization easier and more cost-effective.
Solution Approach 2:
Traditional mechanical packaging methods are replaced with wafer-level bonding techniques. This substitution enables precise fabrication and packaging of miniaturized SAW elements using automated semiconductor processes, reducing manufacturing complexity and cost.
3Ease of manufacture
If a simple packaging structure is used, then manufacturing cost is reduced, but electrical connection reliability may be compromised
Solution Approach 1:
Electrical connections are established through vertical via holes in the cap wafer rather than through lateral wire bonds. This dimensional change from 2D wire bonding to 3D vertical connections improves reliability while maintaining manufacturing simplicity through direct plating processes.
Solution Approach 2:
The cap wafer incorporates multiple materials including conductive fill materials for via holes and bonding materials for wafer attachment. This composite structure ensures reliable electrical connections and hermetic sealing while maintaining manufacturing efficiency.
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 proposed solution enables miniaturization of the SAW device package, reduces manufacturing complexity and costs, and improves electrical characteristics by allowing for a more compact design and efficient electrical connections, while maintaining a hermetic seal.
Implementation Method 1
a second metal layer which is formed on the first metal layer to fill the second via portion, to be electrically connected with the cap pad
Data Source
AI summary
A wafer level package for a surface acoustic wave (SAW) device and a fabrication method thereof. The SAW device wafer level package includes a SAW device in which a SAW element is formed on a top surface of a device wafer, a cap wafer which is bonded with a top surface of the SAW device and has a viahole penetrating the cap wafer, and a conductive member to fill a part of the viahole. The viahole has a first via portion and a second via portion, the first via portion has a gradually smaller diameter from a bottom surface of the cap wafer until a certain depth, and the second via portion has a gradually greater diameter from the first via portion until a top surface of the cap wafer.