Filter Device Wiring Exposed to Reduce IMD
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Solution Overview
Problem
Filter devices used in communication terminals experience intermodulation distortion (IMD) and harmonic wave distortion, particularly when handling both WiFi and Band 7 frequency bands, which deteriorates reception sensitivity.
Innovation Solution
The filter device includes a substrate with piezoelectricity, an IDT electrode, a terminal electrode, and wiring electrodes, where at least a portion of the wiring electrodes are not covered with a dielectric film to prevent current obstruction, and an air layer is used to reduce dielectric constant, thereby reducing IMD and harmonic wave distortion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a dielectric film is provided to cover the IDT electrode for moisture resistance, then moisture resistance is improved, but current flow in wiring electrodes is obstructed causing IMD and harmonic wave distortion
Solution Approach 1:
The dielectric film is selectively formed only in regions where moisture resistance is needed (over IDT electrodes and substrate), while deliberately leaving wiring electrodes exposed. This local differentiation allows the system to achieve moisture protection where required without causing current flow obstruction in wiring regions.
Solution Approach 2:
The dielectric film coverage is segmented into specific regions rather than providing uniform coverage across all electrodes. The film is divided into first and second dielectric films that cover different areas, with wiring electrodes intentionally excluded from coverage to maintain electrical performance.
2Reliability
If wiring electrodes are covered with dielectric film for protection, then moisture resistance is improved, but current flow is obstructed deteriorating reception sensitivity
Solution Approach 1:
The dielectric film coverage is locally applied only to regions requiring moisture protection (IDT electrodes and substrate areas), while wiring electrodes are deliberately left uncovered. This localized approach ensures moisture resistance is achieved where critical without compromising the electrical conductivity and signal quality of wiring electrodes.
3Object-generated harmful factors
If the entire wiring electrode is left uncovered to prevent current obstruction, then IMD and harmonic wave distortion are reduced, but moisture resistance is compromised
Solution Approach 1:
The dielectric film is selectively applied only to regions where moisture resistance is critical (IDT electrodes and substrate), while wiring electrodes are left exposed to prevent current obstruction. This creates different protective qualities in different locations, optimizing both moisture resistance and electrical performance.
Solution Approach 2:
The dielectric protection is segmented into specific zones rather than providing uniform coverage. The first dielectric film covers the IDT electrode area while the second dielectric film covers other substrate regions, with wiring electrode areas intentionally excluded to maintain current flow quality.
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 effectively reduces or prevents IMD and harmonic wave distortion, improving reception sensitivity by minimizing current obstruction and maintaining moisture resistance.
Implementation Method 1
a substrate having piezoelectricity
Data Source
AI summary
A filter device includes a substrate having piezoelectricity, a first filter including an IDT electrode disposed on the substrate, a terminal electrode disposed on the substrate, a first wiring electrode disposed on the substrate and connecting the first filter and a terminal electrode, and a dielectric film disposed above the substrate to cover the IDT electrode. At least a portion of the first wiring electrode is not covered with the dielectric film.