Piezoelectric Bulk Wave Structure to Prevent Layer Cracking

Resolve Bottlenecks,
Find Innovative SolutionsGenerate Solutions

Solution Overview

Problem

Piezoelectric bulk wave devices with through holes in the support body can experience stress concentration at the boundary between supported and unsupported regions of the piezoelectric layer, leading to potential cracking.

Innovation Solution

A piezoelectric bulk wave device design featuring a cavity portion in the support that superposes over the functional electrode and the entirety or substantial entirety of the piezoelectric layer, ensuring the layer is supported by the electrode rather than the support, thereby reducing stress concentration and preventing cracks.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Device complexity

If a through hole is provided in the support body to reduce weight or simplify structure, then manufacturing complexity is reduced, but stress concentration occurs at the boundary between supported and unsupported regions of the piezoelectric layer leading to potential cracking

Engineering Contradiction:

Improvesupport body structureVSAvoidpiezoelectric layer integrity

Core Design Contradiction:

Device complexityVSReliability

Solution Approach 1:

The patent introduces a filling material as an intermediary substance that occupies the through hole space and provides mechanical support to the piezoelectric layer. This filling material acts as a mediator between the support body and the piezoelectric layer, preventing direct contact at the through hole boundary that would cause stress concentration and cracking.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The patent applies beforehand cushioning by filling the through hole with a material that cushions and distributes the stress before it can concentrate at the boundary. The filling material is placed in advance to prevent the harmful stress concentration effect from occurring when the device operates.

Inventive Principle:

Principle #11Beforehand cushioning (Prior cushioning)

2Volume of moving object

If the piezoelectric layer is made thinner to reduce device size, then miniaturization is achieved, but the layer becomes more susceptible to stress-induced cracking

Engineering Contradiction:

Improvedevice sizeVSAvoidpiezoelectric layer resistance to cracking

Core Design Contradiction:

Volume of moving objectVSStrength

Solution Approach 1:

The filling material provides beforehand cushioning by being positioned in the through hole to cushion and distribute stresses before they can concentrate on the thin piezoelectric layer, preventing cracking while allowing the layer to remain thin for miniaturization.

Inventive Principle:

Principle #11Beforehand cushioning (Prior cushioning)

Solution Approach 2:

The patent changes the physical parameters of the support structure by introducing a filling material with specific mechanical properties that alter the stress distribution pattern, allowing the piezoelectric layer to be made thinner without sacrificing its cracking resistance.

Inventive Principle:

Principle #35Parameter changes

3Reliability

If a cavity portion is added to the support body to improve stress distribution, then piezoelectric layer reliability is enhanced, but manufacturing complexity increases

Engineering Contradiction:

Improvepiezoelectric layer crack preventionVSAvoidsupport body structure

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The support body is segmented by creating a through hole that is then filled with a separate material. This segmentation allows the filling material to independently provide stress distribution functionality without requiring complex integrated structures, simplifying the overall manufacturing process.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The support body becomes a composite structure combining the support body material with the filling material in the through hole. This composite structure achieves improved stress distribution and piezoelectric layer protection while maintaining relatively simple manufacturing processes for each component.

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

The design effectively prevents cracks in the piezoelectric layer, enhancing the device's reliability and stability by distributing stress evenly, thus maintaining the electrical characteristics and operational performance.

Implementation Method 1

When an alternating-current voltage is applied across the electrodes, the bulk wave in the thickness slip mode is excited

Methodology Applied

Scientific EffectPiezoelectric effect: Piezoelectric Effect

Data Source

PatentUS20240097643A1Piezoelectric bulk wave device and method for manufacturing the same

Publication Date: 2024.03.21 MURATA MFG CO LTD

AI summary

A piezoelectric bulk wave device includes a support including a support substrate, a piezoelectric layer including a first main surface on the support side and a second main surface opposite from the first main surface, and at least one functional electrode including at least a portion on at least one of the first and second main surfaces. The at least one functional electrode is supported by the support and includes a functional electrode including a portion on the first main surface of the piezoelectric layer. A cavity portion is provided in the support and superposed on a portion of the functional electrode and an entirety or substantially an entirety of the piezoelectric layer in plan view. The piezoelectric layer is supported by the functional electrode supported by the support.