Inkjet Head Substrate Recess and Rounded Corners for Thermal Stress
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Solution Overview
Problem
Ink jet recording heads face issues with thermal stresses leading to broken wires and variations in calorific value due to imperfect insulation and thermal deformation, especially when high-speed, high-definition recording is required, which affects the durability and film quality of the heat generating resistive layer.
Innovation Solution
A method of manufacturing a substrate with a heat generating resistive layer that covers electrode layers, where a recess is formed in the insulative layer between the electrode layers, and the heat generating resistive layer is bent in a U-shape within this recess, reducing thermal stress and improving film quality, and the step coverage of protective films is enhanced by forming a rounded corner on the electrode layer edges.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the electrode layer is formed with a small inclination angle to improve insulation coverage, then the insulative protective layer can better cover the rising portion, but the bottom end portion of the electrode layer becomes prone to breaking and position accuracy errors increase
Solution Approach 1:
The patent applies curvature by rounding the corner portions of the electrode layer instead of forming sharp angles. This rounded configuration reduces stress concentration at the corners, preventing breaking while maintaining adequate insulation coverage. The curved transition smoothly connects the inclined portion to the bottom end, eliminating the weak point that would occur with acute angles.
2Stability of the object's composition
If the heat generating resistive layer is made hard to prevent thermal deformation, then thermal deformation is suppressed, but the film quality deteriorates and broken wires occur due to thermal stresses
Solution Approach 1:
The patent applies local quality by creating a recess portion in the insulative protective layer directly above the corner portions of the electrode layer. This localized structural modification allows the heat generating resistive layer to be deposited into the recess, forming a U-shaped configuration that reduces thermal stress concentration at critical corners while maintaining the necessary thermal stability of the overall layer structure.
3Use of energy by moving object
If the insulative protective layer is made thin to improve heat transfer efficiency, then heat transmission to ink is enhanced, but the protective function against cavitation and insulation is compromised
Solution Approach 1:
The patent applies curvature by forming rounded corner portions in the insulative protective layer. This curved geometry improves step coverage by the subsequent metal protective layer, allowing the protective layers to conform smoothly to the underlying structure. The rounded corners enable adequate protective thickness to be maintained while minimizing the insulative layer thickness for optimal heat transfer.
Data Source
AI summary
In order to form a more homogenous heat generating resistive layer, the present invention provides a method of manufacturing a substrate for an ink jet recording head having a support which has an insulative layer on its surface, a pair of electrode layers disposed on the surface of the support, and a heat generating resistive layer which continuously covers the pair of electrode layers and a section between the pair of electrode layers. The method includes the step of forming an electrode layer on the support and the step of forming the pair of electrode layers by etching the electrode layer. In the step of forming the pair of electrode layers by etching the electrode layer, by etching a surface portion of the insulative layer positioned between the pair of insulative layers, a recess is formed in the surface portion of the insulative layer.