Joined Substrate Bulging Structure for Void-Free Droplet Heads

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Solution Overview

Problem

Existing droplet ejection heads face issues with substrate breakage and void formation during joining due to weak substrate strength at regions with channel grooves, leading to reduced yield and functionality.

Innovation Solution

A joined substrate configuration where a first substrate with grooves and bulging portions in the back surface regions is formed, enhancing strength and preventing void formation by adjusting substrate thickness locally to prevent breakage and voids during joining.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If the substrate is thinned to form channel grooves, then the droplet ejection head functionality is improved, but the substrate strength becomes weak and breakage occurs during joining

Engineering Contradiction:

Improvedroplet ejection head functionalityVSAvoidsubstrate strength

Core Design Contradiction:

Adaptability or versatilityVSStrength

Solution Approach 1:

The patent applies local quality by forming a thickened portion at a specific location (the joining surface) of the substrate. This thickened portion is created by controlling the etching depth to be smaller at the region corresponding to the joining surface, thereby locally increasing substrate thickness and strength only where needed for joining, while maintaining the thin profile elsewhere for channel functionality.

Inventive Principle:

Principle #3Local quality

2Strength

If pressure is applied during joining to ensure adhesion, then joining strength is improved, but voids form on the joining surface due to weak substrate strength

Engineering Contradiction:

Improvejoining strengthVSAvoidjoining surface quality

Core Design Contradiction:

StrengthVSManufacturing precision

Solution Approach 1:

The patent applies beforehand cushioning by pre-forming a thickened portion at the joining surface before the joining process. This thickened portion acts as a cushion that prevents void formation during pressing, allowing adequate pressure to be applied for strong adhesion without causing voids, since the thickened region provides a buffer zone.

Inventive Principle:

Principle #11Beforehand cushioning (Prior cushioning)

3Volume of moving object

If the substrate is made thinner to reduce overall device size, then device compactness is improved, but the substrate becomes more prone to breakage during joining

Engineering Contradiction:

Improvedevice sizeVSAvoidsubstrate integrity during joining

Core Design Contradiction:

Volume of moving objectVSReliability

Solution Approach 1:

The patent maintains overall device compactness by keeping the substrate thin in most regions, while locally thickening the substrate at the joining surface. This local quality approach allows the device to remain compact while ensuring sufficient strength and reliability at the critical joining area.

Inventive Principle:

Principle #3Local quality

Data Source

PatentUS12502888B2Joined substrate, droplet ejection head, and method of manufacturing joined substrate

Publication Date: 2025.12.23 CANON KK

AI summary

Provided is a joined substrate in which a first substrate, a second substrate, and a third substrate are joined in this order with an adhesive agent therebetween, the joined substrate comprising: one or more grooves formed in a groove region of a surface of the first substrate not facing the second substrate; and a bulging portion formed in a back region of a surface of the second substrate not facing the first substrate, the bulging portion bulging in a thickness direction, the back region corresponding to the groove region in a plane direction.