Liquid Ejection Head Through-Hole Electrode Wiring Resistance
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Solution Overview
Problem
Liquid ejection heads face challenges in minimizing wiring resistance while ensuring the reliability of through-hole electrodes and maintaining a short distance between the ejection orifice surface and the recording medium, as conventional bonding wires and sealing materials can interfere with the recording medium.
Innovation Solution
A liquid ejection head design featuring a multilayer wiring layer with a through-hole electrode that is electrically connected to multiple wiring layers, allowing the electrode to be thickened without projecting from the surface, thus reducing wiring resistance while maintaining reliable sealing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of moving object
If a bonding wire is employed for wiring, then the wiring structure is simple, but the distance between the ejection orifice surface and the recording medium cannot be reduced below a limit due to wire projection
Solution Approach 1:
The patent transitions from surface-level wiring (bonding wires on the surface) to through-hole wiring that passes through the substrate in the depth dimension. This dimensional change allows the wiring to be embedded within the substrate rather than protruding from it, enabling the ejection orifice surface to be positioned closer to the recording medium without wire interference.
Solution Approach 2:
The through-hole electrode is nested within the through-hole of the substrate, with the insulating layer enveloping the electrode within the hole. This nesting structure allows the wiring to be contained within the substrate volume rather than occupying surface space, eliminating the projection problem while maintaining electrical connectivity.
2Length of moving object
If a through-hole electrode is used to replace bonding wire, then the distance between ejection orifice surface and recording medium can be reduced, but the wiring resistance of the through-hole electrode increases
Solution Approach 1:
The patent changes the cross-sectional area parameter of the through-hole electrode by making the hole diameter larger relative to the substrate thickness. This parameter change reduces the wiring resistance while still achieving the goal of minimizing the distance between the ejection orifice surface and the recording medium.
Solution Approach 2:
The patent uses a composite structure consisting of the through-hole electrode material combined with the insulating layer material. This composite approach allows the electrode to be optimized for low resistance while the insulating layer provides protective and sealing functions, achieving both low resistance and reliable sealing.
3Reliability
If the through-hole electrode is made thick to reduce wiring resistance, then the wiring resistance decreases, but the electrode projects from the surface and compromises sealing reliability
Solution Approach 1:
The patent introduces an insulating layer as an intermediary substance that fills the space between the thick through-hole electrode and the ejection orifice forming member. This intermediary material provides the necessary sealing function while allowing the electrode to maintain its thick cross-section for low resistance, resolving the contradiction between resistance reduction and sealing reliability.
4Ease of manufacture
If bonding wire and sealing material are used, then wiring is simple, but they project toward the recording medium and interfere with it
Solution Approach 1:
The patent extracts the wiring function from the surface level and relocates it to the through-hole structure within the substrate. By taking out the wiring from the surface environment, the bonding wire and sealing material no longer project toward the recording medium, eliminating the interference problem while maintaining manufacturability through standard through-hole fabrication processes.
Data Source
AI summary
A liquid ejection head includes, a multilayer wiring layer having a plurality of wiring layers laid one on the other and an insulating layer enveloping the plurality of wiring layers, an ejection orifice forming member arranged on one of the oppositely disposed surfaces of the multilayer wiring layer and having an ejection orifice formed therethrough to eject liquid and a through-hole electrode arranged in a through hole running through the multilayer wiring layer between the one and the other surfaces of the multilayer wiring layer. The plurality of wiring layers includes a first wiring layer having a surface located closest to the ejection orifice forming member and the through-hole electrode is held in contact with at least one surface of the plurality of wiring layers different from the surface of the first wiring layer and is electrically connected to the plurality of wiring layers.