Liquid Ejection Head Back Surface Wiring Bonding
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Solution Overview
Problem
Existing methods for connecting recording element substrates and electric wiring substrates in liquid ejection heads require bonding to a support member, leading to increased manufacturing costs and risks of corrosion due to the proximity of adhesive and sealants to the liquid supply port, which can block the port and cause electrical failures.
Innovation Solution
A liquid ejection head design where the recording element substrate and flexible electric wiring substrate are electrically connected without a support member, with the bonding occurring between the liquid supply port and the edge of the substrate, ensuring a distance between the electric connection and the liquid supply port to prevent interference and corrosion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the recording element substrate and electric wiring substrate are bonded to a support member and electrically connected, then electrical connection is established, but the adhesive agent and sealant may overflow to the liquid supply port and block it, increasing manufacturing cost and reducing reliability
Solution Approach 1:
The patent changes the spatial arrangement by bonding the electric wiring substrate to the back surface (second face) of the recording element substrate, positioning the electric connection part on the opposite side from the liquid supply port. This dimensional separation ensures that adhesive agent and sealant applied during bonding cannot overflow to block the liquid supply port, while still establishing reliable electrical connection through wire bonding or other electrical bonding methods.
Solution Approach 2:
The patent introduces a back surface bonding structure as an intermediary arrangement, where the electric wiring substrate is bonded to the back surface of the recording element substrate rather than directly to the front surface near the liquid supply port. This intermediary positioning acts as a spatial buffer that prevents harmful overflow while maintaining electrical connectivity.
2Reliability
If through-wiring is formed to pass through the recording element substrate and coated with conductive material, then electrical connection is achieved, but many additional processing steps are required, increasing processing cost and device complexity
Solution Approach 1:
The patent extracts the through-wiring structure and replaces it with surface-level electrical connection methods. Instead of forming conductive coatings on through-holes that penetrate the substrate, the invention uses wire bonding or other electrical bonding techniques that connect pads on the front surface to the electric wiring substrate bonded on the back surface, eliminating the need for complex through-wiring formation and conductive coating processes.
Solution Approach 2:
The patent inverts the conventional approach by bonding the electric wiring substrate to the back surface rather than the front surface, and establishing electrical connections through this inverted configuration. This inversion eliminates the need for through-wiring that would require drilling, plating, and coating operations, simplifying the manufacturing process.
3Area of stationary object
If the electric connection part and liquid supply port are positioned close to each other, then compact design is achieved, but the risk of liquid contact with electric wiring causing corrosion increases
Solution Approach 1:
The patent resolves the conflict between compact design and corrosion prevention by utilizing the third dimension (depth/thickness) of the substrate. By bonding the electric wiring substrate to the back surface and positioning the electric connection part on the opposite side from the liquid supply port, the invention creates spatial separation in the vertical dimension, preventing liquid contact with electric wiring while maintaining a compact overall structure.
Data Source
AI summary
A recording element substrate is bonded to an FPC in at least a part of a region of a second face between a liquid supply port and an edge of the recording element substrate, and an electric connection part is provided in which a wiring conductor and a pad are electrically connected to each other by a bonding wire.