Acoustic Wave Insulator Stack for Moisture-Resistant Filtering

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Solution Overview

Problem

Conventional acoustic wave devices used in mobile communications suffer from reliability issues due to parasitic factors and moisture sensitivity, particularly when exposed to high moisture conditions over a long duration, leading to degradation of resin materials and compromised high-frequency filtering characteristics.

Innovation Solution

The acoustic wave device employs a combination of inorganic and organic insulators to suppress parasitic factors and enhance moisture resistance, featuring inorganic insulators with a silicon nitride layer and organic insulators like polyimide, which are strategically layered to cover wiring intersections and the piezoelectric substrate, forming a robust oscillation space that protects against hydrolytic reactions and maintains high-frequency performance.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Loss of energy

If resin material insulators are used to suppress parasitic factors, then high-frequency characteristics are improved, but reliability deteriorates under high moisture conditions due to damage to the resin material

Engineering Contradiction:

Improveparasitic factorsVSAvoidreliability under high moisture condition

Core Design Contradiction:

Loss of energyVSReliability

Solution Approach 1:

The patent applies composite materials by combining organic insulator material (resin) and inorganic insulator material in a layered structure. The organic insulator suppresses parasitic factors with its low dielectric constant, while the inorganic insulator provides moisture resistance, thus resolving the contradiction between improving high-frequency characteristics and maintaining reliability under high moisture conditions.

Inventive Principle:

Principle #40Composite materials

2Loss of energy

If thick insulator layers are used to suppress parasitic factors, then high-frequency characteristics are improved, but device complexity increases

Engineering Contradiction:

Improveparasitic factorsVSAvoidinsulator layer structure

Core Design Contradiction:

Loss of energyVSDevice complexity

Solution Approach 1:

The patent segments the insulator function into two distinct layers: an organic insulator layer for suppressing parasitic factors and an inorganic insulator layer for providing moisture resistance. This segmentation allows each layer to be optimized for its specific function with appropriate thickness, avoiding the need for a single thick insulator layer and thus reducing overall device complexity.

Inventive Principle:

Principle #1Segmentation

3Reliability

If inorganic insulator only is used, then moisture resistance is improved, but parasitic factor suppression deteriorates due to high dielectric constant

Engineering Contradiction:

Improvemoisture resistanceVSAvoidparasitic factors

Core Design Contradiction:

ReliabilityVSLoss of energy

Solution Approach 1:

The patent uses composite materials where the organic insulator layer (with low dielectric constant) is combined with the inorganic insulator layer (with high moisture resistance). This composite structure allows the organic layer to suppress parasitic factors effectively while the inorganic layer provides the necessary moisture resistance, resolving the contradiction between these two requirements.

Inventive Principle:

Principle #40Composite materials

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 parasitic effects, improves moisture resistance, and enhances the reliability and high-frequency characteristics of the acoustic wave device, ensuring stable performance even under high moisture conditions.

Implementation Method 1

an inorganic insulator covering at least a second portion of an upper surface of the organic insulator... The second portion of the upper surface of the organic insulator faces an oscillation space across the inorganic insulator

Methodology Applied

Scientific EffectDielectric isolation: Dielectric

Implementation Method 2

The acoustic wave device includes the piezoelectric substrate made of a single crystal piezoelectric substance, such as lithium tantalate or lithium niobate, and comb-shaped electrodes disposed on a surface of the piezoelectric substrate

Methodology Applied

Scientific EffectPiezoelectric effect: Piezoelectric Effect

Data Source

PatentUS9099981B2Acoustic wave device having an inorganic insulator and an organic insulator

Publication Date: 2015.08.04 SKYWORKS PANASONIC FILTER SOLUTIONS JAPAN

AI summary

An acoustic wave device includes a piezoelectric substrate, a first wiring disposed on an upper surface of the piezoelectric substrate, an organic insulator covering at least a portion of the first wiring, a second wiring disposed on a first portion of the upper surface of the organic insulator, and an inorganic insulator covering at least a second portion of an upper surface of the organic insulator. The second portion of the upper surface of the organic insulator faces an oscillation space across the inorganic insulator. The acoustic wave device has preferable high-frequency characteristics and high long-term reliability.