Liquid Ejection Head Substrate Supply Path Etching
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Solution Overview
Problem
Existing methods for manufacturing liquid ejection head substrates face challenges in reducing the lateral size of the liquid ejection head and preventing adhesive squeezing into supply paths, which can lead to reduced production efficiency and bubble releasability issues.
Innovation Solution
The liquid ejection head substrate features supply paths with a cross-sectional shape that tapers from the second surface to the first surface, with a mechanism to reduce adhesive squeezing, comprising regions with different inclinations to the first surface, and using an etching method that involves anisotropic etching with a specific etchant containing polyethylene glycol to control the etching rate and path width.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of moving object
If the amount of engraving by dry etching is increased to increase the opening width of supply paths in the first surface, then the opening width is improved, but the time taken for dry etching is increased which reduces production efficiency
Solution Approach 1:
The patent changes the etching parameters by introducing a two-stage etching process: first performing dry etching to create initial through-holes, then performing anisotropic wet etching to laterally expand the openings. This parameter change allows achieving larger opening widths without proportionally increasing dry etching time, thus resolving the contradiction between opening width and production efficiency
Solution Approach 2:
The patent combines two different etching methods (dry etching and anisotropic wet etching) into a composite processing approach. Each method contributes its strengths: dry etching provides precise through-hole formation, while anisotropic wet etching provides lateral expansion. This composite approach achieves both sufficient opening width and maintained production efficiency
2Device complexity
If the same etching mask layer is used for both dry etching and anisotropic etching, then the process is simplified, but the opening width of supply paths is limited by the mask layer opening width and dry etching engraving amount
Solution Approach 1:
The patent segments the etching function into two distinct stages with different mask layers: the first mask layer (photoresist) is used only for dry etching to form through-holes, and the second mask layer is used for anisotropic wet etching to expand the openings. This segmentation allows each mask layer to be optimized for its specific function, enabling greater opening width achievement
3Strength
If adhesive is applied to the peripheral portion of the liquid ejection head substrate for mounting, then the substrate is securely fixed, but the adhesive is squeezed into the supply paths which blocks liquid flow and reduces bubble releasability
Solution Approach 1:
The patent performs preliminary action by forming protrusions on the substrate surface at locations corresponding to supply path openings before the adhesive application step. These protrusions act as barriers that prevent adhesive from being squeezed into the supply paths during mounting, thus preserving bubble releasability while maintaining secure fixation
Solution Approach 2:
The protrusions formed on the substrate surface serve as an intermediary structure between the adhesive and the supply path openings. This intermediary physical barrier allows the adhesive to provide secure mounting strength while simultaneously preventing it from entering the supply paths and blocking liquid flow
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 downsizing of the liquid ejection head substrate, reduces adhesive squeezing, and enhances bubble releasability by maintaining a smaller opening width and preventing adhesive blockage in the supply paths.
Implementation Method 1
the silicon substrate is further anisotropically etched using the same etching mask layer
Implementation Method 2
a silicon (111) plane which has a relatively low etching rate and which is inclined at 54.7° to a (100) plane is formed using the anisotropic etching of silicon
Implementation Method 3
an etching method that involves anisotropic etching with a specific etchant containing polyethylene glycol to control the etching rate and path width
Data Source
AI summary
The wall of each supply path formed in a silicon substrate has such a shape that a plurality of regions distinguished from each other due to different inclinations to a first surface of the silicon substrate are connected to each other between the first surface and a second surface of the silicon substrate and the width of the supply path is maintained or expands from the first surface to second surface of the silicon substrate. An internal opening is formed by one of the regions that is most steeply inclined to the first surface of the silicon substrate. A region reducing the squeezing of an adhesive into the internal opening is placed between the internal opening and the second surface of the silicon substrate.