SAW Duplexer Reflector Layout for Resin-Molding Reliability
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Solution Overview
Problem
The existing surface acoustic wave devices face challenges in miniaturization and maintaining filter characteristics due to potential deformation of the lid during resin molding, which can lead to contact with the IDT electrode and subsequent degradation of filter and resonance characteristics.
Innovation Solution
A surface acoustic wave device design featuring a piezoelectric substrate with IDT electrodes and reflectors on both sides, an insulator member forming a closed space with a weighted reflector and inclined sidewall, and a through-type electrically conductive member for surface mounting, reducing the area of the closed space and preventing deformation during resin molding.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the lid is made thinner to achieve miniaturization and flat design, then the device size is reduced, but the lid becomes prone to deformation during resin molding which may cause contact with the IDT electrode and degradation of filter characteristics
Solution Approach 1:
The patent performs preliminary action by forming a protrusion on the lid before resin molding, and positioning a support structure in the closed space to prevent lid deformation during the subsequent resin molding process. This preliminary preparation ensures the thin lid maintains its shape and prevents contact with the IDT electrode, resolving the contradiction between miniaturization and reliability.
2Reliability
If a closed space is formed to prevent vibration impediment, then the acoustic wave performance is maintained, but the device occupies more space and becomes bulkier
Solution Approach 1:
The patent applies nesting by placing the support structure inside the closed space formed by the lid and substrate. The support structure is nested within the existing closed space, providing structural reinforcement without adding external volume. This allows the device to maintain both the necessary closed space for acoustic wave performance and a compact overall size.
3Length of stationary object
If the lid is positioned close to the IDT electrode to reduce device height, then miniaturization is achieved, but any deformation or contact between the lid and IDT electrode will severely degrade filter characteristics
Solution Approach 1:
The patent introduces an intermediary element - the support structure positioned in the closed space between the lid and IDT electrode. This intermediary prevents direct contact between the lid and IDT electrode even when the device is miniaturized, acting as a mechanical buffer that maintains the necessary clearance and prevents degradation of filter characteristics due to manufacturing variations or deformation.
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 design effectively prevents deformation of the insulator member and maintains reliable filter characteristics, ensuring the surface acoustic wave device remains functional and resistant to characteristic degradation even with further miniaturization and flat design implementation.
Implementation Method 1
A formation region of the IDT electrode is excited with an alternating current applied to the IDT electrode
Implementation Method 2
a surface acoustic wave device including reflectors arranged in a surface acoustic wave traveling direction on both sides of a region of an IDT electrode
Data Source
AI summary
A surface acoustic wave device in which miniaturization and a flat design implemented, is resistant to a deformation responsive to a pressure of a molten resin in the formation of a mold resin layer, and is less susceptible to a characteristic degradation. In the surface acoustic wave device, an IDT electrode is located on a piezoelectric substrate, and an insulator member is arranged such that a space B surrounding the IDT electrode is provided. For the purpose of reducing the area of the space B, reflectors having weighted portions are arranged on both sides of the IDT electrode. The weighted portions include electrode fingers of the reflectors that become shorter in length as they extend farther away from the IDT electrode. The shape of the space B is reduced accordingly.