Planar Micro-Fluid Ejection Head Bonding
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Solution Overview
Problem
Current micro-fluid ejection head manufacturing processes face challenges in maintaining the position and alignment of ejection device substrates and nozzle plates, particularly for larger ejection swaths, due to thermal expansion mismatches and warping caused by adhesive curing, limiting the production of substantially planar devices.
Innovation Solution
A method involving a silicon device substrate with fluid flow slots hermetically sealed to a silicon support material using a basic solution, such as tetramethylammonium hydroxide (TMAH), at controlled temperatures and pressures, forming a covalent bond that eliminates the need for heat curing and reduces material costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If adhesive die-bonding material is used to secure the device substrate to support material, then the components are bonded together, but thermal curing causes expansion and contraction leading to warping or bowing of the ejection device substrate and nozzle plate
Solution Approach 1:
The patent removes the adhesive layer entirely from the bonding process. Instead of using adhesive die-bonding material that requires thermal curing, the invention directly bonds the device substrate to the support substrate through a controlled thermal process that creates a metallurgical bond without intermediate adhesive materials, thereby eliminating the warping and bowing caused by adhesive curing
Solution Approach 2:
The patent replaces the chemical bonding mechanism (adhesive die-bonding) with a thermal-field bonding mechanism. By applying controlled heat and pressure directly to the substrate interfaces, a metallurgical bond is formed without requiring adhesive materials or their subsequent thermal curing, thus avoiding the expansion-contraction cycle that causes warping
2Manufacturing precision
If adhesive die-bonding material is used to secure the device substrate to support material, then the components are bonded together, but alterations in adhesive layer thickness or support material thickness have led to only marginal improvements in planarity
Solution Approach 1:
The patent eliminates the adhesive layer and its associated thickness control problems. By removing the intermediate adhesive material, the bonding process no longer requires precise control of adhesive layer thickness, and the support substrate can be designed with optimal thickness for planarity without being constrained by adhesive layer variations
Solution Approach 2:
The patent changes the bonding parameters from chemical-adhesive-based to thermal-field-based bonding. This parameter change allows direct control over the bonding interface through temperature and pressure parameters, enabling better planarity control through optimized thermal processing rather than relying on adhesive layer thickness adjustments
3Area of stationary object
If larger ejection chips with larger ejection swaths are manufactured, then the ejection capability is increased, but maintaining position and alignment between ejection chip and nozzle plate becomes more difficult due to CTE mismatches
Solution Approach 1:
The patent employs substrates with matched thermal expansion properties (both being silicon or silicon-based materials) to create a homogeneous thermal response across the entire assembly. This homogeneity in material properties ensures that even large ejection chips maintain alignment with the nozzle plate during thermal processing, as all components expand and contract uniformly
Solution Approach 2:
The patent replaces adhesive-based mechanical bonding with thermal-field bonding that creates a metallurgical bond between substrates. This substitution eliminates the CTE mismatch issues that arise with adhesive materials, allowing large ejection chips to maintain precise alignment with nozzle plates through direct substrate-to-substrate bonding of compatible materials
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 allows for the production of substantially planar micro-fluid ejection heads with improved alignment and reduced warping, achieving a hermetic seal resistant to fluid degradation and enabling larger ejection chip sizes while minimizing material costs.
Implementation Method 1
hermetically sealed using a basic solution to a support material
Implementation Method 2
depositing a basic solution on a first surface of a device substrate sufficient to wet the first surface of the device substrate
Implementation Method 3
achieving a hermetic seal resistant to fluid degradation
Data Source
AI summary
A process for making a substantially planar micro-fluid ejection head is disclosed, and includes depositing a basic solution on a first surface of a device substrate. The first surface having the basic solution deposited thereon is contacted together with a surface of a support material for a duration ranging from about 1 minute to about 15 minutes, at a temperature ranging from about 20° C. to about 90° C. so that the first surface having the basic solution deposited thereon and the surface of the support material form a bond therebetween to hermetically seal the support material and the device substrate to one another. Both the substrate and the at least one surface of the support comprise silicon, and at least one of the device substrate and the at least one surface of the support material is substantially composed of silicon.