Piezoelectric Vibrating Device Wiring Board Bonding

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Solution Overview

Problem

In vibrating devices with piezoelectric elements, the mechanical load on the connection between the wiring board and the diaphragm can lead to a decrease in reliability due to vibration-induced stress, causing physical and electrical disconnections between the wiring board and the piezoelectric element.

Innovation Solution

The solution involves bonding the piezoelectric element and the wiring board to the diaphragm's principal plane, using a resin film and conductors covered with a coating film, which enhances the physical bonding strength between the piezoelectric element and the diaphragm, and ensures electrical insulation, thereby reducing mechanical load on the connection points and preventing disconnections.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If the wiring board is physically connected to the diaphragm, then electrical connection between the wiring board and piezoelectric element is achieved, but mechanical load acts on the connection portion causing deterioration of physical and electrical connections

Engineering Contradiction:

Improveconnection reliabilityVSAvoidconnection strength

Core Design Contradiction:

ReliabilityVSStrength

Solution Approach 1:

The patent introduces an intermediary structure where the wiring board is bonded to the diaphragm through a bonding region that distributes mechanical stress. The wiring board includes conductors embedded in a resin layer, with the conductors electrically connecting the piezoelectric element to external terminals while the resin layer provides mechanical cushioning against vibration-induced stress concentration at connection points.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Speed

If the wiring board is bonded to the diaphragm, then displacement transmission from piezoelectric element to diaphragm is efficient, but the wiring board and piezoelectric element may separate under vibration

Engineering Contradiction:

Improvedisplacement transmission efficiencyVSAvoidconnection reliability

Core Design Contradiction:

SpeedVSReliability

Solution Approach 1:

The wiring board is segmented into distinct functional regions: a bonding region that contacts the diaphragm for efficient displacement transmission, a conductor region with embedded conductors for electrical connection, and a terminal region for external connections. This segmentation allows each region to optimize its function while reducing stress concentration at interfaces.

Inventive Principle:

Principle #1Segmentation

3Reliability

If the conductors are exposed for electrical connection, then electrical connection is achieved, but mechanical load directly acts on the conductor connection portion

Engineering Contradiction:

Improveelectrical connection reliabilityVSAvoidmechanical load on conductors

Core Design Contradiction:

ReliabilityVSForce

Solution Approach 1:

The resin layer serves as an intermediary material that embeds the conductors, providing both electrical insulation and mechanical protection. The conductors are exposed only at necessary connection points while the resin layer distributes mechanical stress away from the conductor-dia phragm interface, reducing direct mechanical load on the electrical connections.

Inventive Principle:

Principle #24Intermediary (Mediator)

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 efficiently transmits displacement from the piezoelectric element to the diaphragm while minimizing mechanical load on the wiring board connections, thereby enhancing the reliability of the vibrating device by reducing the likelihood of physical and electrical disconnections.

Implementation Method 1

A vibrating device including a piezoelectric element... The piezoelectric element body contains a piezoelectric material

Methodology Applied

Scientific EffectPiezoelectric effect: Piezoelectric Effect

Implementation Method 2

The third principal plane and the side surface are bonded to the first principal plane... displacement of the piezoelectric element is efficiently transmitted to the diaphragm

Methodology Applied

Scientific EffectElastic deformation: Elasticity

Data Source

PatentUS10825980B2Vibrating device

Publication Date: 2020.11.03 TDK CORP

AI summary

A vibrating device includes a diaphragm, a piezoelectric element, and a wiring board. The piezoelectric element and the wiring board are bonded to a first principal plane of the diaphragm. The wiring board is electrically connected with the piezoelectric element. The piezoelectric element includes a piezoelectric element body, a plurality of internal electrodes, and a plurality of external electrodes. The piezoelectric element body has a second principal plane, a third principal plane, and a side surface. The third principal plane and the side surface are bonded to the first principal plane. The wiring board has a resin film, a plurality of conductors, and a coating film. The coating film is disposed on the plurality of conductors in such a way as to cover the plurality of conductors. One end portions of the plurality of conductors are exposed from the coating film and electrically connected with corresponding external electrodes.