Elastic Wave Device Inductor Surface Smoothing
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Solution Overview
Problem
Conventional elastic wave devices face challenges in maintaining high Q-factor and inductance characteristics due to difficulties in forming conductive traces on piezoelectric substrates, often requiring additional inductors and experiencing variations in inductance and dielectric loss.
Innovation Solution
The elastic wave device incorporates a resin layer with a lower filler density between the insulator and inductor electrodes, smoothing the surface and reducing dielectric loss, while using a filler-rich insulator to maintain physical strength and prevent moisture ingress, thereby improving high-frequency characteristics and reducing inductance variations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional insulator with uniform filler density is used, then the insulator provides adequate physical strength and moisture protection, but the surface roughness causes variations in inductance and increases dielectric loss
Solution Approach 1:
The insulator is designed with non-uniform filler density: a first region adjacent to the inductor electrode contains filler particles with a first average diameter, while a second region contains filler particles with a second average diameter. This local differentiation allows the surface region to provide smoothness for stable inductance while the bulk maintains physical strength and moisture protection.
Solution Approach 2:
The insulator uses a composite structure with two different filler particle sizes distributed in the resin matrix. This composite approach enables simultaneous achievement of contradictory properties: smooth surface for low dielectric loss and stable inductance, while maintaining bulk mechanical strength and moisture barrier properties.
2Reliability
If additional separate inductors are added to achieve required inductance and Q-factor, then the electrical characteristics are improved, but the device complexity and size increase
Solution Approach 1:
The insulator is integrated with the inductor electrode structure, where the insulator's filler particle distribution is specifically optimized to work in conjunction with the inductor trace. This merging eliminates the need for separate additional inductors while achieving the required electrical characteristics through the insulator-inductor interaction.
3Manufacturing precision
If the insulator surface is made smooth to reduce inductance variations, then inductance stability improves, but the insulator may lose physical strength and moisture protection
Solution Approach 1:
The insulator employs spatially differentiated filler distribution: smaller filler particles in the region adjacent to the inductor electrode provide surface smoothness for precise inductance control, while larger filler particles in the bulk region provide mechanical strength and moisture barrier properties. This local quality differentiation resolves the contradiction between surface smoothness and bulk strength.
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 enhances the high-frequency electrical characteristics of inductor electrodes, stabilizes inductance, and minimizes variations, achieving excellent performance even under high molding pressures, suitable for use in mobile telecommunications apparatuses.
Implementation Method 1
piezoelectric substrate
Data Source
AI summary
An elastic wave device includes an interdigital transducer (IDT) electrode disposed on an upper surface of a piezoelectric substrate, a wiring electrode disposed on the upper surface of the piezoelectric substrate and connected to the IDT electrode, and a first insulator layer disposed on the upper surface of the piezoelectric substrate. The first insulator layer seals the IDT electrode and the wiring electrode and includes a first resin and a first filler. A resin layer including no filler is provided on an upper surface of the first insulator layer. An inductor electrode is disposed on an upper surface of the resin layer. A second insulator layer is disposed on the upper surface of the resin layer and covers the inductor electrode. A terminal electrode is disposed on an upper surface of the second insulator layer. A connecting electrode electrically connects the wiring electrode, the terminal electrode, and the inductor electrode.