Piezoelectric Filter Structure for Moisture-Resistant Hollow Cavities
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Solution Overview
Problem
Existing filter devices, such as acoustic wave devices and piezoelectric substrate-based filters, face reliability issues due to moisture entering the vibration space or hollow portion from outside, which can decrease the device's performance and longevity.
Innovation Solution
A filter device design that includes a piezoelectric substrate, a lid, a support, an insulating layer, and a through conductor, where the insulating layer has a cavity with a specific star-shaped hexagonal shape, and the through conductor has an insertion portion and a shoulder portion, is used to reduce moisture entry into the hollow portion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional filter device structure is used, then the device can be manufactured with standard processes, but moisture enters the hollow portion from outside along interfaces between layers, decreasing reliability
Solution Approach 1:
The insulating layer is segmented into multiple regions: a first insulating layer region and a second insulating layer region with different thicknesses. This segmentation creates a stepped structure that prevents moisture penetration along the interface while maintaining manufacturing feasibility through standard layering processes.
Solution Approach 2:
The patent introduces a dimensional variation in the insulating layer thickness, transitioning from a two-dimensional uniform layer to a three-dimensional stepped structure. This dimensional change creates an additional barrier against moisture entry along the interface between the support and insulating layer.
2Reliability
If the insulating layer thickness is increased to prevent moisture entry, then moisture resistance improves, but manufacturing complexity and cost increase
Solution Approach 1:
Instead of uniformly increasing the insulating layer thickness throughout, the layer is segmented into regions of different thicknesses. The first insulating layer region maintains standard thickness for ease of manufacture, while the second insulating layer region provides enhanced thickness specifically where moisture penetration risk exists at the interface.
Solution Approach 2:
The insulating layer thickness is optimized locally rather than globally. The second insulating layer region provides increased thickness specifically at the interface area where moisture entry is most likely, while other areas maintain standard thickness, thus improving moisture resistance without proportionally increasing manufacturing complexity.
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 design effectively reduces moisture entry into the hollow portion, thereby enhancing the reliability and performance of the filter device by preventing thermal stress and maintaining heat conduction functionality.
Implementation Method 1
The through conductor includes an insertion portion inside the cavity and a shoulder portion on a virtual boundary surface with the insertion portion. A portion between a portion of the cavity located outside the edge of the shoulder portion and the insertion portion is filled with a portion of the support.
Implementation Method 2
The piezoelectric substrate includes a main surface on which a functional element and a conductive layer electrically connected to the functional element are disposed.
Data Source
AI summary
An insulating layer includes a cavity in a portion covering a conductive layer. A through conductor includes an insertion portion inside the cavity and a shoulder portion on a virtual boundary surface with the insertion portion when viewed in a direction parallel or substantially parallel to a main surface. The cavity is located alternately outside and inside an edge of the shoulder portion in a circumferential direction of the shoulder portion when viewed in a direction orthogonal or substantially orthogonal to the main surface. A portion between a portion of the cavity located outside the edge of the shoulder portion and the insertion portion is filled with a portion of the support when viewed in the direction orthogonal or substantially orthogonal to the main surface.