Acoustic Wave Device Resin Interface for Migration Prevention
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Solution Overview
Problem
Acoustic wave devices experience electrochemical migration issues due to the contact between extended wiring lines and sealing resin layers, leading to short circuits, which existing technologies have not adequately addressed.
Innovation Solution
The acoustic wave device incorporates a second resin portion with a lower Young's modulus and filler content than the first resin portion, positioned between the element substrate and the first resin portion, and an interface located closer to the mount substrate than the extended wiring lines, preventing the movement of metallic substances and reducing electrochemical migration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a sealing resin layer is formed to cover the protective layer, then the acoustic wave device is sealed and protected, but electrochemical migration occurs at the interface between the protective layer and sealing resin layer causing short circuits
Solution Approach 1:
A second resin portion is introduced as an intermediary layer between the element substrate and the first resin portion (sealing resin). This intermediate layer positions the resin-resin interface closer to the mount substrate than the extended wiring lines, thereby preventing direct contact between the sealing resin interface and the wiring lines, which eliminates the pathway for electrochemical migration while maintaining device sealing.
Solution Approach 2:
The second resin portion is specifically positioned only in the region between the element substrate and the first resin portion, with its interface strategically located closer to the mount substrate than the extended wiring lines. This localized structural modification addresses the electrochemical migration issue at the critical interface region without altering the overall sealing function of the first resin portion.
2Reliability
If the interface between resin portions is located closer to the mount substrate than the extended wiring lines, then electrochemical migration is prevented, but the device structure becomes more complex
Solution Approach 1:
The second resin portion is integrated with the existing protective layer structure, merging the protective and sealing functions into a unified resin system. The interface between the first and second resin portions is positioned to serve dual purposes: maintaining device sealing while preventing electrochemical migration, thereby reducing the need for additional separate protective structures.
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 configuration significantly reduces or prevents electrochemical migration between extended wiring lines, enhancing the reliability of the acoustic wave device and reducing the risk of short circuits.
Implementation Method 1
an interface between the protective layer and the sealing resin layer is in contact with both the extended wiring lines adjacent to each other, and thus electrochemical migration may occur in which a metallic substance included in the extended wiring lines moves outward along the interface
Data Source
AI summary
An acoustic wave device includes a functional electrode provided on a first main surface of an element substrate, extended wiring lines that are electrically connected to the functional electrode and that are adjacent to each other on a second main surface facing away from the first main surface, external terminals that are connected to the extended wiring lines, respectively, and that are provided on the second main surface, a first resin portion that seals the acoustic wave device, and a second resin portion that is provided at a position which is between the element substrate and the first resin portion and which is on the second main surface.