Liquid Ejection Head Substrate with Local Adhesive Thickening

Solution Overview

Problem

The existing liquid ejection head substrates face damage to the covering layer due to loads during bonding, warpage of substrates, and stress from temperature changes, which can occur when the covering layer is thin and in contact with or adjacent to the wiring.

Innovation Solution

A liquid ejection head substrate design that includes a spacer to increase the thickness of the adhesive layer over the covering layer on the wiring, ensuring it is greater than the adhesive thickness in other areas, thereby reducing stress and preventing damage to the covering layer.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Volume of moving object

If the covering layer is made thin to reduce overall device thickness, then the device becomes more compact, but the covering layer becomes susceptible to damage from bonding loads, warpage stress, and thermal expansion

Engineering Contradiction:

Improveoverall device thicknessVSAvoidcovering layer integrity

Core Design Contradiction:

Volume of moving objectVSReliability

Solution Approach 1:

The adhesive layer thickness is made non-uniform, being thicker in regions where the covering layer contacts or is adjacent to wiring and thinner in other regions. This local variation in adhesive thickness provides enhanced stress protection precisely where the covering layer is most vulnerable, while maintaining overall device compactness.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

A thicker adhesive layer is intentionally provided in advance in critical regions before bonding occurs. This pre-positioned thicker adhesive layer acts as a cushion that absorbs bonding loads, warpage stress, and thermal expansion forces, preventing damage to the thin covering layer before such damage can occur.

Inventive Principle:

Principle #11Beforehand cushioning (Prior cushioning)

2Ease of manufacture

If uniform adhesive thickness is used during substrate bonding, then the bonding process is simpler, but the covering layer may still be damaged by concentrated stress at wiring locations

Engineering Contradiction:

Improvebonding process simplicityVSAvoidcovering layer protection

Core Design Contradiction:

Ease of manufactureVSReliability

Solution Approach 1:

The adhesive layer is designed with spatially varying thickness, being thicker in regions where the covering layer contacts or is adjacent to wiring and thinner in other regions. This local variation in adhesive thickness provides enhanced stress protection precisely where the covering layer is most vulnerable, while maintaining overall device compactness.

Inventive Principle:

Principle #3Local quality

3Reliability

If the adhesive layer is made uniformly thick to protect the covering layer, then the covering layer is better protected from stress, but the overall device thickness increases

Engineering Contradiction:

Improvecovering layer protectionVSAvoidoverall device thickness

Core Design Contradiction:

ReliabilityVSVolume of moving object

Solution Approach 1:

The adhesive layer thickness is made non-uniform, being thicker in regions where the covering layer contacts or is adjacent to wiring and thinner in other regions. This local variation in adhesive thickness provides enhanced stress protection precisely where the covering layer is most vulnerable, while maintaining overall device compactness.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

A thicker adhesive layer is intentionally provided in advance in critical regions before bonding occurs. This pre-positioned thicker adhesive layer acts as a cushion that absorbs bonding loads, warpage stress, and thermal expansion forces, preventing damage to the thin covering layer before such damage can occur.

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 spacer design effectively suppresses damage to the covering layer by distributing stress more evenly, maintaining the integrity of the substrate and ensuring reliable operation of the liquid ejection head.

Implementation Method 1

The spacer design effectively suppresses damage to the covering layer by distributing stress more evenly

Methodology Applied

Scientific EffectStress distribution:

Data Source

PatentUS20250276523A1Liquid ejection head substrate and method for manufacturing liquid ejection head substrate

Publication Date: 2025.09.04 CANON KK

AI summary

A technique capable of suppressing the occurrence of damage to a covering layer is provided. A liquid ejection head substrate including an energy generation element for imparting energy to liquid includes a first substrate, a second substrate including a bonded surface bonded to a bonded surface of the first substrate via an adhesive and provided with wiring connected to the energy generation element and a covering layer covering the wiring, and a member provided on the bonded surface of at least one of the first substrate and the second substrate and in a position where the member does not overlap the wiring in a direction in which the first substrate and the second substrate are laminated, the member having a height so that a second thickness of the adhesive on the covering layer provided on the wiring is greater than a first thickness of the adhesive on the member.