Piezoelectric Filter Reinforcement Film for Border Crack Prevention

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Solution Overview

Problem

Piezoelectric layers in existing devices are prone to damage at the border between regions overlapping and not overlapping with space portions, leading to potential cracking and delamination.

Innovation Solution

Incorporation of reinforcement films on the upper and lower surfaces of the piezoelectric layer, which overlap with the border between overlapping and non-overlapping regions, providing structural support and reducing or preventing damage.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a space portion is provided in the support to reduce weight or improve acoustic performance, then device performance is improved, but the piezoelectric layer becomes prone to damage at the border between overlapping and non-overlapping regions

Engineering Contradiction:

Improvepiezoelectric layer integrityVSAvoidpiezoelectric layer strength at border

Core Design Contradiction:

ReliabilityVSStrength

Solution Approach 1:

A reinforcement film is provided at the specific location of the border between the region overlapping with the space portion and the region not overlapping with the space portion. This local reinforcement targets the vulnerable area without affecting other regions, preventing cracking and delamination while maintaining the overall device design with the space portion.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The support structure is formed as a composite comprising the support substrate, the piezoelectric layer, and the reinforcement film. This composite structure combines the lightweight and acoustic benefits of the space portion with the mechanical strength provided by the reinforcement film at critical locations.

Inventive Principle:

Principle #40Composite materials

2Length of moving object

If the piezoelectric layer is made thinner to reduce device size, then device compactness is improved, but the piezoelectric layer becomes more susceptible to damage and cracking

Engineering Contradiction:

Improvepiezoelectric layer thicknessVSAvoidpiezoelectric layer resistance to cracking

Core Design Contradiction:

Length of moving objectVSStrength

Solution Approach 1:

The reinforcement film is strategically positioned at the border region where cracking is most likely to occur, providing localized strength enhancement. This allows the piezoelectric layer to be made thinner overall while maintaining sufficient strength at the critical vulnerability point.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The reinforcement film is provided in advance before the piezoelectric layer is subjected to operational stresses. This preliminary reinforcement prevents cracking from initiating at the border region, enabling the use of thinner piezoelectric layers that would otherwise be too fragile.

Inventive Principle:

Principle #10Preliminary action

3Reliability

If electrodes are extended to cover the entire piezoelectric layer surface to improve electrical contact, then electrical performance is improved, but the risk of delamination at the border regions increases

Engineering Contradiction:

Improveelectrical contact qualityVSAvoidpiezoelectric layer delamination resistance

Core Design Contradiction:

ReliabilityVSStability of the object's composition

Solution Approach 1:

The reinforcement film is specifically positioned at the border regions where delamination is most likely to occur, providing localized mechanical support that prevents separation between the piezoelectric layer and the support substrate, even when electrodes are extensively applied.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The reinforcement film acts as a preventive measure against delamination at the border regions. By providing this reinforcement in advance, the structure can withstand the stress of extensive electrode application and subsequent operational use without delamination occurring.

Inventive Principle:

Principle #11Beforehand cushioning (Prior cushioning)

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 reinforcement films effectively reduce or prevent cracking and delamination of the piezoelectric layer at the border, enhancing the device's structural integrity and enabling frequency characteristic adjustments through electrical capacitance.

Implementation Method 1

the reinforcement film overlaps with at least a portion of a border between a region overlapping with the space portion and a region not overlapping with the space portion

Methodology Applied

Scientific EffectMechanical support:

Implementation Method 2

enabling frequency characteristic adjustments through electrical capacitance

Methodology Applied

Scientific EffectPiezoelectric effect: Piezoelectric Effect

Data Source

PatentUS20260076094A1Piezoelectric device and piezoelectric filter

Publication Date: 2026.03.12 MURATA MFG CO LTD

AI summary

A piezoelectric device includes a piezoelectric layer including a thickness in a first direction, and upper and lower surfaces, a support on a side of the lower surface of the piezoelectric layer, an upper electrode on the upper surface of the piezoelectric layer, a lower electrode on the lower surface of the piezoelectric layer with at least a portion of the lower electrode facing the upper electrode, and a reinforcement film on at least one of the upper and lower surfaces of the piezoelectric layer. The support includes a space portion in a region overlapping with at least a portion of the upper and lower electrodes. In plan view seen in the first direction, the reinforcement film overlaps with at least a portion of a border between a region overlapping with the space portion and a region not overlapping with the space portion.