SAW Filter Layout Using Narrow Grooves for Pyroelectric Isolation

Solution Overview

Problem

Conventional SAW filters have low productivity and high costs due to the complex process of forming conductor removing parts on piezoelectric substrates, which are necessary to prevent pyroelectric breakdown during manufacturing.

Innovation Solution

The SAW filter design incorporates conductor removing portions in the form of narrow grooves and pattern portions on the substrate, allowing the surface acoustic wave devices to remain non-conductive and reducing the need for extensive conductor removal, thereby simplifying the manufacturing process and reducing costs.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If conductor removing parts are provided at most places of the piezoelectric substrate except for the surface acoustic wave device and reflectors, then pyroelectric breakdown is prevented, but manufacturing complexity increases and productivity decreases

Engineering Contradiction:

Improveprevention of pyroelectric breakdownVSAvoidmanufacturing efficiency

Core Design Contradiction:

ReliabilityVSProductivity

Solution Approach 1:

The conductor removing parts are segmented into specific strategic locations rather than being uniformly distributed across the entire substrate. The conductor removing parts are positioned at locations where conductor patterns converge or where potential difference exists, providing pyroelectric breakdown prevention only where needed rather than across the whole substrate.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Conductor removing parts are provided only at specific local positions where conductor patterns are present and where pyroelectric breakdown risk exists. The patent specifies that conductor removing parts are positioned at locations adjacent to surface acoustic wave devices or reflectors where conductor patterns converge, rather than uniformly across the entire substrate, optimizing both protection and manufacturing efficiency.

Inventive Principle:

Principle #3Local quality

2Reliability

If conductor removing parts are provided at most places of the piezoelectric substrate, then pyroelectric breakdown is prevented, but manufacturing process becomes difficult and costs increase

Engineering Contradiction:

Improveprevention of pyroelectric breakdownVSAvoidmanufacturing process simplicity

Core Design Contradiction:

ReliabilityVSEase of manufacture

Solution Approach 1:

The conductor removing parts are segmented into specific strategic locations rather than being uniformly distributed across the entire substrate. The conductor removing parts are positioned at locations where conductor patterns converge or where potential difference exists, providing pyroelectric breakdown prevention only where needed rather than across the whole substrate.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Conductor removing parts are provided only at specific local positions where conductor patterns are present and where pyroelectric breakdown risk exists. The patent specifies that conductor removing parts are positioned at locations adjacent to surface acoustic wave devices or reflectors where conductor patterns converge, rather than uniformly across the entire substrate, optimizing both protection and manufacturing efficiency.

Inventive Principle:

Principle #3Local quality

3Reliability

If extensive conductor removal is performed to form conductor removing parts, then pyroelectric breakdown is prevented, but manufacturing time and costs increase

Engineering Contradiction:

Improveprevention of pyroelectric breakdownVSAvoidmanufacturing cycle time

Core Design Contradiction:

ReliabilityVSLoss of time

Solution Approach 1:

The conductor removing parts are segmented into specific strategic locations rather than being uniformly distributed across the entire substrate. The conductor removing parts are positioned at locations where conductor patterns converge or where potential difference exists, providing pyroelectric breakdown prevention only where needed rather than across the whole substrate.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Conductor removing parts are provided only at specific local positions where conductor patterns are present and where pyroelectric breakdown risk exists. The patent specifies that conductor removing parts are positioned at locations adjacent to surface acoustic wave devices or reflectors where conductor patterns converge, rather than uniformly across the entire substrate, optimizing both protection and manufacturing efficiency.

Inventive Principle:

Principle #3Local 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 design enhances productivity by simplifying the manufacturing process, reducing signal leakage, and achieving strong isolation between surface acoustic wave devices, while maintaining the integrity of the filter without pyroelectric breakdown.

Implementation Method 1

a piezoelectric substrate, and a plurality of surface acoustic wave devices formed on one side of the piezoelectric substrate

Methodology Applied

Scientific EffectPiezoelectric effect: Piezoelectric Effect

Data Source

PatentUS7498905B2SAW filter and method of manufacturing the same

Publication Date: 2009.03.03 QORVO US INC

AI summary

In an SAW filter on one side of a piezoelectric substrate are formed a pattern portion constituted by a conductor and provided on the outer circumferential portion of the surface acoustic wave device, and a conductor removing portion formed between the surface acoustic wave device and the pattern portion. The shape of the surface acoustic wave device is formed by the conductor removing portion and the surface acoustic wave device remains non-conductive with the pattern by the conductor removing portion.