Elastic Wave Device Identification Marking Parasitic Capacitance
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Solution Overview
Problem
Elastic wave devices with metal identification patterns suffer from increased propagation loss due to parasitic capacitance, and enlarging the distance between the identification pattern and IDT electrode to mitigate this issue results in increased device size.
Innovation Solution
An elastic wave device with a piezoelectric substrate, interdigital transducer electrode, wire, and electrically insulating film, where the identification marking is defined by an uneven portion of the electrically insulating film that does not overlap the interdigital transducer electrode, reducing propagation loss and allowing for a smaller device size.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of information
If an identification pattern is made of a metal material, then chip identification is enabled, but radio-frequency signal leakage occurs through parasitic capacitance between the IDT electrode and the identification pattern
Solution Approach 1:
An electrically insulating film is introduced as an intermediary between the metal identification pattern and the IDT electrode. This insulating film prevents direct electrical interaction while allowing the identification pattern to remain in close proximity to the IDT electrode, thus eliminating parasitic capacitance effects and signal leakage without increasing device size.
2Reliability
If the distance between the identification pattern and the IDT electrode is increased to prevent signal leakage, then parasitic capacitance effects are reduced, but the device size increases
Solution Approach 1:
The electrically insulating film serves as a mediator that enables the identification pattern to be positioned close to the IDT electrode without creating harmful parasitic capacitance. This resolves the contradiction by maintaining small device dimensions while preventing signal leakage through the insulating property of the film.
Solution Approach 2:
The electrical properties of the space between the identification pattern and IDT electrode are changed by introducing the insulating film. This parameter change (from conductive to insulating) allows close spacing without parasitic capacitance effects, thus maintaining small device size while ensuring low propagation loss.
3Reliability
If a separate protective film is added to prevent signal leakage, then propagation loss is reduced, but device complexity and size increase
Solution Approach 1:
The protective film and the insulating film are merged into a single integrated structure. The electrically insulating film simultaneously provides both protection for the IDT electrode and prevention of parasitic capacitance effects, eliminating the need for separate protective and insulating layers, thus reducing device complexity while maintaining low propagation loss.
Solution Approach 2:
The electrically insulating film performs multiple functions: it protects the IDT electrode from environmental damage, prevents parasitic capacitance between the identification pattern and IDT electrode, and maintains mechanical stability. This multi-functionality reduces the number of separate components needed, thereby simplifying device structure.
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 solution effectively reduces deterioration of surface acoustic wave propagation characteristics and enables a compact design by utilizing an electrically insulating film for both protection and identification, preventing nonuniform frequency changes and minimizing the device's size.
Implementation Method 1
The substrate has piezoelectricity
Implementation Method 2
a radio-frequency signal that propagates through the IDT electrode may leak through a parasitic capacitance that occurs between the IDT electrode and the identification pattern
Data Source
AI summary
An elastic wave device includes a substrate, an IDT electrode, a wire, an electrically insulating film, and an identification marking. The substrate has piezoelectricity. The IDT electrode is provided on the substrate and includes a pair of comb-shaped electrodes facing each other. The wire is provided on the substrate and connected to the IDT electrode. The electrically insulating film is provided at least on the IDT electrode and the wire. The identification marking is defined by an uneven portion of a surface of the electrically insulating film. The identification marking does not to overlap the IDT electrode in plan view of the substrate.