Liquid Ejecting Head Protrusion Swelling for Electrical Coupling

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Solution Overview

Problem

In liquid ejecting heads, the expansion of adhesive agents and bump electrodes due to moisture absorption leads to insufficient electrical coupling between the sealing plate and the substrate, disrupting the connection between the drive signal and the piezoelectric elements.

Innovation Solution

A liquid ejecting head design featuring a first substrate with a drive element and a first wire, a second substrate with an opposing surface adhered using an adhesive agent, and an elastically deformable protrusion that electrically couples the first and second wires, with a swelling ratio of the protrusion greater than the adhesive agent, ensuring consistent electrical connection.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If adhesive agent and bump electrodes are used to bond substrates, then electrical coupling is achieved, but moisture absorption causes expansion and distances substrates away, reducing electrical coupling

Engineering Contradiction:

Improveelectrical couplingVSAvoiddistance between substrates

Core Design Contradiction:

ReliabilityVSStability of the object's composition

Solution Approach 1:

The patent changes the swelling ratio parameter of the adhesive agent by selecting specific materials (acrylic resin, polyurethane resin, or silicone resin with controlled hydrophilicity) to ensure the adhesive expands less than the substrate in humid environments, maintaining electrical coupling between bump electrodes and lower electrodes despite moisture absorption

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent uses composite material selection by combining specific resin types (acrylic, polyurethane, or silicone) with controlled hydrophilic characteristics to create an adhesive composition that balances bonding strength with minimal expansion upon moisture absorption, resolving the contradiction between achieving electrical coupling and maintaining substrate distance stability

Inventive Principle:

Principle #40Composite materials

2Quantity of substance

If adhesive agent absorbs moisture and expands, then volume increases, but the sealing plate and substrate become distanced away, losing electrical coupling

Engineering Contradiction:

Improvevolume of adhesive agentVSAvoidelectrical coupling

Core Design Contradiction:

Quantity of substanceVSReliability

Solution Approach 1:

The patent controls the swelling ratio parameter of the adhesive agent by selecting materials with specific hydrophilic characteristics, ensuring that even when the adhesive absorbs moisture and its volume increases, the expansion is insufficient to distance the substrates beyond the point where electrical coupling is lost

Inventive Principle:

Principle #35Parameter changes

3Reliability

If bump electrodes and adhesive agent are used for bonding, then electrical connection is established, but expansion upon moisture absorption disrupts the connection

Engineering Contradiction:

Improveelectrical connectionVSAvoidmoisture absorption

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The patent changes the swelling ratio parameter by selecting adhesive materials (acrylic resin, polyurethane resin, or silicone resin) with controlled hydrophilicity to minimize expansion upon moisture absorption, thereby preventing disruption of the electrical connection between bump electrodes and lower electrodes in humid environments

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent converts the harmful effect of moisture absorption into a beneficial outcome by selecting adhesive materials that expand in a controlled manner, ensuring that the expansion does not exceed the threshold that would disrupt electrical coupling, thus maintaining reliable connections despite the presence of moisture

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

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 maintains sufficient electrical coupling between the wires, even in humid environments, by increasing the pressing force through the protrusion's higher swelling ratio, thus ensuring reliable operation of the liquid ejecting head.

Implementation Method 1

a protrusion configured to elastically deform, the protrusion being formed between the first substrate and the second substrate and electrically coupling the first wire and the second wire to each other

Methodology Applied

Scientific EffectElastic deformation: Elasticity

Implementation Method 2

a swelling ratio of the protrusion is larger than a swelling ratio of the adhesive agent

Methodology Applied

Scientific EffectSwelling: Absorption (physical)

Data Source

PatentUS10850519B2Liquid ejecting head and liquid ejecting apparatus

Publication Date: 2020.12.01 SEIKO EPSON CORP

AI summary

A liquid ejecting head including a first substrate in which a drive element that ejects a liquid from a nozzle, and a first wire electrically coupled to the drive element are formed, a second substrate in which an opposing surface that opposes the first substrate is adhered to the first substrate with an adhesive agent, a second wire being formed in the second substrate, and a protrusion configured to elastically deform, the protrusion being formed between the first substrate and the second substrate and electrically coupling the first wire and the second wire to each other. In the liquid ejecting head, a swelling ratio of the protrusion is larger than a swelling ratio of the adhesive agent.