Micro-Fluid Ejection Head Covalent Bonding

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Solution Overview

Problem

Current micro-fluid ejection head manufacturing processes struggle to maintain planarity, particularly for ejection heads with swath dimensions greater than 2.5 centimeters, due to mismatched thermal expansion coefficients between components, leading to warping and bowing issues.

Innovation Solution

A micro-fluid ejection head with a substantially planar device substrate covalently bonded to a planar support material without adhesives, using a silicon oxide bonding layer and reactive functional groups to form a hermetic seal at room temperature, eliminating thermal expansion-related distortions.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Strength

If adhesive die-bonding material is used to secure components, then components are secured to one another, but thermal curing causes expansion and contraction leading to warping or bowing of the ejection device substrate and nozzle plate

Engineering Contradiction:

Improvebonding strengthVSAvoidplanarity

Core Design Contradiction:

StrengthVSShape

Solution Approach 1:

The bonding process parameters are changed from thermal curing at high temperatures to room temperature covalent bonding. This eliminates the thermal expansion and contraction cycle that causes warping, while still achieving strong bonding through chemical functional group reactions between the adhesive layer and substrate surfaces.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The mechanical/thermal bonding process is replaced with a chemical bonding process. Instead of using heat and pressure to cure adhesives, the patent uses covalent bonding through reactive functional groups that form chemical bonds at room temperature, eliminating thermal stress-induced deformation.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

2Strength

If adhesive material is used to bond components, then components are secured together, but the adhesive layer thickness variations lead to only marginal improvements in planarity

Engineering Contradiction:

Improvebonding strengthVSAvoidplanarity tolerance

Core Design Contradiction:

StrengthVSManufacturing precision

Solution Approach 1:

The bonding mechanism is changed from mechanical adhesion dependent on layer thickness to covalent chemical bonding. This allows for thin adhesive layers with consistent bonding strength regardless of thickness variations, significantly improving planarity control and manufacturing precision.

Inventive Principle:

Principle #35Parameter changes

3Area of stationary object

If larger ejection chips with greater ejection swath dimensions are manufactured, then ejection capacity is increased, but maintaining planarity becomes more difficult due to amplified warping effects

Engineering Contradiction:

Improveejection swath dimensionVSAvoidplanarity

Core Design Contradiction:

Area of stationary objectVSShape

Solution Approach 1:

The bonding process is changed from thermal curing to room temperature covalent bonding, eliminating thermal stress that causes warping. This allows larger ejection chips to be manufactured while maintaining planarity, as the chemical bonding process does not induce the thermal expansion and contraction that amplify warping effects in larger substrates.

Inventive Principle:

Principle #35Parameter changes

4Strength

If thermal curing is used to cure adhesive, then bonding is achieved, but mismatched coefficients of thermal expansion between components cause warping or bowing

Engineering Contradiction:

Improvebonding strengthVSAvoiddimensional stability

Core Design Contradiction:

StrengthVSStability of the object's composition

Solution Approach 1:

The thermal bonding process is replaced with chemical bonding at room temperature. By using covalent bonds formed through reactive functional groups, the patent eliminates the thermal expansion mismatch issue that occurs when different materials are heated to different extents during adhesive curing, thereby maintaining dimensional stability.

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 approach ensures a planar ejection head with improved hermetic sealing and reduced warping, suitable for larger ejection chips, by forming covalent bonds at room temperature, which are resistant to fluid degradation and thermal expansion issues.

Implementation Method 1

The first surface of the device substrate is covalently bound to a substantially planar support

Methodology Applied

Scientific EffectCovalent bonding: Chemical Bonding

Implementation Method 2

The activated surfaces are coated with a reactive functional group and subsequently contacted with one another thereby covalently bonding the support material and the device substrate to one another

Methodology Applied

Scientific EffectChemical bonding through reactive functional groups: Chemical Bonding

Implementation Method 3

depositing a thin film of silicon oxide onto a surface of a substantially planar support material

Methodology Applied

Scientific EffectPhysical vapor deposition: Physical Vapour Deposition

Data Source

PatentUS7735952B2Method of bonding a micro-fluid ejection head to a support substrate

Publication Date: 2010.06.15 BRADY WORLDWIDE INC

AI summary

A substantially planar micro-fluid ejection device, where the micro-fluid ejection head is covalently bound to a substantially planar support material, and a method of making the same.