Low Shear Modulus Adhesive for Micro-Fluid Ejection Heads
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Solution Overview
Problem
Conventional adhesive materials used in micro-fluid ejection heads are non-flexible and brittle due to high curing temperatures, leading to issues like bowing, cracking, and separation of components, resulting in fluid leakage and malfunctioning of the ejection heads.
Innovation Solution
A thermally curable adhesive composition with a low shear modulus of less than 10 MPa at 25°C and a glass transition temperature of less than 65°C is developed, which is suitable for attaching micro-fluid ejection heads to device structures, reducing residual stresses and improving mechanical and adhesive properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If conventional adhesive materials are used with high curing temperatures, then the adhesive provides strong bonding, but the adhesive becomes non-flexible and brittle causing chip cracking and component separation
Solution Approach 1:
The patent changes the chemical composition parameters of the adhesive by incorporating flexible polymers and plasticizers to reduce the shear modulus and glass transition temperature, allowing the adhesive to remain flexible at lower curing temperatures while maintaining bonding strength
Solution Approach 2:
The patent uses composite adhesive materials combining multiple polymer components with different properties to achieve both strong bonding and flexibility, creating an adhesive that resists chipping and cracking while maintaining structural integrity
2Strength
If high temperature curing is used to ensure complete adhesive cure, then the adhesive achieves full bonding strength, but the ejection device structure expands and contracts causing stress and bowing
Solution Approach 1:
The patent changes the curing temperature parameter to a lower range, which prevents excessive thermal expansion and contraction of the ejection device structure while still achieving complete adhesive cure, thereby reducing thermal stress and bowing
Solution Approach 2:
The patent introduces a flexible adhesive composition as an intermediary that accommodates thermal expansion differences between dissimilar components through its low shear modulus and reduced glass transition temperature, acting as a buffer against thermal stress
3Reliability
If the adhesive is made more flexible to reduce brittleness, then the adhesive resists cracking better, but the adhesive becomes less resistant to chemical degradation by ejected fluids
Solution Approach 1:
The patent develops composite adhesive formulations that combine flexible polymer components with fluid-resistant additives, creating an adhesive that maintains both flexibility and chemical resistance to ejected fluids through synergistic material properties
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 use of this adhesive composition reduces substrate bowing, increases durability, and enhances planarity of the ejection heads, providing improved mechanical and ink-resistant properties while minimizing stress and fragility.
Implementation Method 1
A thermally curable adhesive composition with a low shear modulus of less than 10 MPa at 25°C and a glass transition temperature of less than 65°C is developed
Data Source
AI summary
Adhesive compositions, micro-fluid ejection devices, and methods for attaching micro-fluid ejection heads to devices. One such adhesive composition is provided for use in attaching a micro-fluid ejection head to a device, such as to reduce chip bowing and/or to decrease chip fragility upon curing of the adhesive. Such an exemplary composition may include one having from about 50.0 to about 95.0 percent by weight of at least one cross-linkable resin selected from the group consisting of epoxy resins, siloxane resins, urethane resins, and functionalized olefin resins; from about 0.1 to about 25.0 percent by weight of at least one thermal curative agent; and from about 0.0 to about 30.0 percent by weight filler, and exhibit a relatively low shear modulus upon curing (e.g., less than about 10.0 MPa at 25° C.).