Flexible Adhesives for Micro-Fluid Ejection Head Durability
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Solution Overview
Problem
Conventional adhesives and encapsulant 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, which result in fluid leakage, corrosion, and malfunctioning of the ejection heads.
Innovation Solution
The use of flexible adhesives and encapsulant materials with a Young's modulus of less than 2000 MPa, a shear modulus of less than 15 MPa at 25°C, and a glass transition temperature of less than 90°C, cured using methods such as thermal, UV, or dual-cure systems, to reduce stress and improve mechanical and corrosion resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If conventional adhesive and encapsulant materials are used with high curing temperatures, then the bonding strength and corrosion resistance are improved, but the materials become non-flexible and brittle causing bowing, cracking, and component separation
Solution Approach 1:
The patent changes the physical and chemical parameters of the adhesive and encapsulant materials by selecting materials with specific glass transition temperatures (below 90°C), Young's moduli (below 2000 MPa), and shear moduli (below 15 MPa). These parameter changes enable the materials to remain flexible at operating temperatures while maintaining adequate bonding strength, thereby preventing bowing and cracking without sacrificing adhesive performance.
2Strength
If rigid adhesive materials are used to maintain structural integrity, then the bonding strength is improved, but the materials cannot accommodate dissimilar thermal expansion coefficients between silicon/ceramic substrates and polymeric ejection device structures
Solution Approach 1:
The patent selects adhesive materials with specific mechanical properties (Young's modulus below 2000 MPa, shear modulus below 15 MPa) that enable the material to flex and accommodate dimensional changes. This parameter selection allows the adhesive to absorb thermal expansion and contraction stresses between dissimilar substrates while maintaining continuous bonding, preventing delamination and structural failure.
Solution Approach 2:
The patent employs composite material systems that combine adhesive and encapsulant materials with tailored mechanical properties. These composite materials are designed to have matched coefficients of thermal expansion and appropriate modulus values that bridge the gap between rigid silicon/ceramic substrates and flexible polymeric structures, enabling both strong bonding and thermal accommodation.
3Strength
If high shear modulus adhesive materials are used for strong bonding, then the bonding strength is improved, but the materials induce high stress during curing and cooling causing components to bow, chip, or separate
Solution Approach 1:
The patent fundamentally changes the mechanical parameter of shear modulus by selecting materials with values below 15 MPa, which is dramatically lower than conventional adhesive materials. This parameter change reduces the material's rigidity, allowing it to deform elastically during curing and cooling processes, thereby absorbing thermal stresses without inducing high stress concentrations that would cause bowing, chipping, or separation.
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 flexible adhesives and encapsulants reduce bowing and warping of micro-fluid ejection heads, enhance durability, and improve planarity, allowing the ejection heads to withstand greater impact and maintain functionality after drops, while providing improved mechanical and corrosion resistance.
Implementation Method 1
the substrate adhesive (e.g., die bond), nozzle plate adhesive, and encapsulant must accommodate both dissimilar expansions and contractions of the micro-fluid ejection head and the ejection device structure
Implementation Method 2
an adhesive is used to bond the ejection head to the ejection device structure. The adhesive 'fixes' the micro-fluid ejection head to the ejection device structure
Data Source
AI summary
Micro-fluid ejection head structures, methods of making micro-fluid ejection head structures having improved operability, and methods for improving the durability of micro-fluid ejection head structures are provided. One such micro-fluid ejection head structure includes a micro-fluid ejection head having a substrate and nozzle plate assembly adhesively attached adjacent to a substrate support using a substrate adhesive. The nozzle plate is adhesively attached adjacent to the substrate with a nozzle plate adhesive. A thermally, UV or other cure mechanism encapsulant material is attached adjacent to the ejection head and substrate support. Each of the substrate adhesive, and the encapsulant material, after curing, have a Young's modulus of less than about 2000 MPa, a shear modulus at 25° C. of less than about 15 MPa, and a glass transition temperature of less than about 90° C.