Liquid Ejection Head Crystal Orientation for Crack Prevention

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Solution Overview

Problem

Liquid ejection heads, such as ink jet recording heads, face issues with substrate cracking and inaccurate formation of reservoir portions due to the susceptibility of silicon single crystal substrates with (110) plane orientation, leading to increased costs and reduced yield.

Innovation Solution

A liquid ejection head design where the flow channel-forming substrate and joining substrate have their first (111) planes oriented perpendicular to each other, preventing cracking and allowing for accurate formation of reservoir portions by anisotropically etching and laser-assisted dicing, thereby improving rigidity and reducing dicing width.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If the first (111) planes of the flow channel-forming substrate and reservoir-forming substrate are oriented in the same direction, then the substrates can be joined together, but cracks occur along the first (111) planes due to susceptibility to cracking

Engineering Contradiction:

Improvesubstrate crack preventionVSAvoidsubstrate orientation alignment

Core Design Contradiction:

ReliabilityVSStability of the object's composition

Solution Approach 1:

The patent applies asymmetry by intentionally misaligning the crystallographic orientations of the two substrates. The flow channel-forming substrate has its first (111) plane oriented in a different direction than the first (111) plane of the reservoir-forming substrate. This asymmetric orientation arrangement prevents cracks from propagating along continuous (111) planes across the joint, while still maintaining proper functional alignment of the substrates.

Inventive Principle:

Principle #4Asymmetry

2Ease of manufacture

If through holes are formed by anisotropic etching to create a break pattern, then dicing lines are formed, but the break pattern width becomes large reducing the number of substrates per wafer

Engineering Contradiction:

Improvedicing line formationVSAvoidsubstrates per wafer

Core Design Contradiction:

Ease of manufactureVSProductivity

Solution Approach 1:

The patent replaces the conventional mechanical/anisotropic etching dicing method with laser beam processing. By focusing a laser beam to form fragile portions at predetermined positions, the break pattern width is significantly reduced compared to traditional anisotropic etching methods. This substitution enables narrower dicing lines and increases the number of substrates that can be produced from a single wafer.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Productivity

If the break pattern width is reduced, then more substrates can be produced from one wafer, but the dicing precision becomes more difficult to achieve

Engineering Contradiction:

Improvesubstrates per waferVSAvoiddicing line precision

Core Design Contradiction:

ProductivityVSManufacturing precision

Solution Approach 1:

The patent employs laser beam technology to achieve precise positioning and formation of fragile portions. The laser beam can be focused to a very small spot size and precisely controlled in position, enabling the formation of narrow break patterns with high precision. This optical approach provides superior positioning accuracy compared to mechanical methods, allowing reduced break pattern width without sacrificing dicing precision.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

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 design effectively prevents substrate cracking and enhances the accuracy of reservoir formation, increasing the number of substrates produced from a single wafer and reducing production costs.

Implementation Method 1

the pressure-generating chambers are formed by anisotropically etching the silicon single crystal substrate

Methodology Applied

Scientific EffectAnisotropic etching:

Implementation Method 2

a laser beam is applied on the first wafer and the second wafer while the laser beam is being focused to a point inside the first and second wafers

Methodology Applied

Scientific EffectLaser heating: Laser

Data Source

PatentUS8162448B2Liquid ejection head and manufacturing method thereof

Publication Date: 2012.04.24 SEIKO EPSON CORP

AI summary

A liquid ejection head includes a flow channel-forming substrate having a plurality of pressure-generating chambers communicated with nozzles for ejecting droplets, the pressure-generating chambers being arranged in parallel with each other; a plurality of pressure-applying units for applying pressure to interiors of the pressure-generating chambers; and a joining substrate joined onto one surface of the flow channel-forming substrate. The flow channel-forming substrate includes a silicon single crystal substrate having a (110) plane orientation and has a side surface extending in a longitudinal direction of the pressure-generating chambers, the side surface being composed of a first (111) plane perpendicular to a (110) plane. The joining substrate includes a silicon single crystal substrate having a (110) plane orientation and is joined onto the flow channel-forming substrate so that a first (111) plane of the joining substrate perpendicular to the (110) plane intersects the first (111) plane of the flow channel-forming substrate.