Acoustic Wave Device Columnar Electrode Void Reduction
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Solution Overview
Problem
Existing acoustic wave devices, such as SAW devices, face issues with reliability due to void formation around columnar electrodes and weak bonding between the protective cover and substrate, leading to increased breakage and connection failures during mounting and usage.
Innovation Solution
The acoustic wave device features a substrate with an acoustic wave element, an outside connection conductor, and a protective cover that surrounds the columnar electrode, reducing void formation and enhancing the contact area and bonding force between the substrate and the protective cover, thereby improving the device's reliability and sealing capabilities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If sealing resin is molded around columnar electrodes to prevent breakage, then electrode protection is improved, but voids form around the electrodes reducing support strength
Solution Approach 1:
The protective cover is formed beforehand to define the vibration space and provide structural support. The frame member is preliminarily shaped to surround the columnar electrodes, creating a supportive framework before the sealing resin is applied. This preliminary structure prevents void formation and ensures proper resin distribution around the electrodes.
Solution Approach 2:
The protective cover acts as an intermediary structure between the columnar electrodes and the external environment. The frame member specifically serves as a mediator that provides mechanical support to the electrodes while allowing the sealing resin to properly bond and fill the spaces, eliminating voids and ensuring reliable electrical connections.
2Strength
If protective cover is added to secure vibration space, then acoustic wave element protection is improved, but bonding force between cover and substrate remains weak
Solution Approach 1:
The frame member is designed with varying cross-sectional dimensions, being wider at the bottom portion that contacts the substrate and narrower at the top portion. This local quality variation ensures strong bonding at the critical substrate interface while maintaining the protective enclosure function at the upper sections. The frame member's geometry is optimized locally to maximize bonding strength where it matters most.
3Volume of moving object
If device size is reduced for surface mount applications, then mounting density is improved, but structural integrity and sealing reliability deteriorate
Solution Approach 1:
The protective cover structure is nested within the overall device footprint, with the frame member efficiently enclosing the vibration space and columnar electrodes in a compact arrangement. The lid member closes the top opening, creating a nested, space-efficient structure that maintains robust sealing and structural integrity while minimizing the device's overall volume for surface mount applications.
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 reduces the likelihood of columnar electrode breakage and maintains a stable, tight seal, resulting in a small-sized and highly reliable acoustic wave device.
Implementation Method 1
a surface acoustic wave (hereinafter, sometimes abbreviated as 'SAW') device
Implementation Method 2
SAW element 2 on one main surface of the piezoelectric substrate 1
Data Source
AI summary
A small and highly reliable acoustic wave device and a method for production of the same will be provided. The acoustic wave device has a piezoelectric substrate 1; a SAW element 2 on one main surface of the piezoelectric substrate 1; an outside connection-use conductor 3 formed on the one main surface of the piezoelectric substrate 1 and electrically connected to the SAW element 2; a columnar electrode 10 on the outside connection-use conductor 3; and a protective cover 6 defining inner walls of a vibration space 7 for vibration of the SAW element 2 and planarly surrounding a side surface of the columnar electrode 10.