Multilayer Fuse Structure for Liquid Discharge Head Durability
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Solution Overview
Problem
The existing liquid discharge heads face issues with the degradation of protective layers due to electrochemical reactions, leading to reduced durability and potential electrical communication between heating resistance elements and protective layers, which can cause deterioration and affect the overall performance of the liquid discharge apparatus.
Innovation Solution
A liquid-discharge-head substrate with a multilayer structure including a base, heating resistance elements, insulating layers, conductive protective layers, fuses, and a common wiring line, where the fuses have a multilayer structure with conductive layers of different oxidizability to facilitate easy blowing and reduce manufacturing burden, thereby preventing electrical communication and enhancing durability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If an insulating layer is disposed between the heating resistance element and the protective layer, then electrical communication between the protective layer and heating resistance element is prevented, but the insulating layer can be degraded causing accidental failure and electrical communication
Solution Approach 1:
The protective layer is divided into a first protective layer covering the heating resistance element and a second protective layer covering the first protective layer. The insulating layer is positioned between the heating resistance element and the first protective layer, creating segmented electrical isolation zones. This segmentation allows the insulating layer to protect specific critical areas while the multilayer protective structure provides overall protection and alternative current paths.
Solution Approach 2:
The fuse is disposed between the first protective layer and a common wiring line to provide beforehand cushioning against electrical failure. When the insulating layer degrades and electrical communication occurs, the fuse blows to disconnect the heating resistance element, preventing damage from uncontrolled current flow. This prior cushioning mechanism protects the system before catastrophic failure can occur.
2Ease of operation
If individual protective layers are connected to each other, then electrical connection allows cleaning through electrochemical reaction, but current may flow to protective layers not in electrical communication with heating resistance elements causing deterioration expansion
Solution Approach 1:
The protective layers are segmented into first and second protective layers with distinct functions. The first protective layer is electrically connected to the heating resistance element and can be cleaned through electrochemical reaction when voltage is applied. The second protective layer covers the first protective layer and provides additional protection. This segmentation allows controlled electrical connection for cleaning while preventing uncontrolled current flow through improperly connected layers.
Solution Approach 2:
The fuse disposed between the first protective layer and the common wiring line provides beforehand cushioning against uncontrolled current flow. When cleaning voltage is applied or when insulating layer degradation causes accidental electrical communication, the fuse blows to disconnect the first protective layer from the common wiring line, preventing current from flowing to the second protective layer that is not in proper electrical communication with the heating resistance element.
3Ease of operation
If fuses are thinned in an additional step to increase ease of blowing, then blowing ease is improved, but manufacturing process complexity increases
Solution Approach 1:
The fuse and the common wiring line are merged into a single multilayer conductive structure formed in the same manufacturing step. The fuse corresponds to a first conductive layer and the common wiring line corresponds to a second conductive layer, both formed simultaneously through the same film formation and patterning processes. This merging eliminates the need for separate fuse thinning steps while maintaining the fuse's ability to blow when excessive current flows, as the first conductive layer has lower thickness and higher resistance compared to the second conductive layer.
Solution Approach 2:
The fuse and common wiring line use different thickness parameters within the multilayer structure. The first conductive layer (fuse) has a thickness of 50 nm while the second conductive layer (common wiring line) has a thickness of 200 nm. This parameter change in thickness provides the necessary resistance difference for the fuse to blow easily under excessive current conditions while maintaining low overall resistance for the common wiring line during normal operation, all achieved in a single manufacturing step.
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
The solution effectively suppresses the degradation of protective layers, increases the ease of blowing fuses, and reduces the manufacturing burden by using a shared multilayer structure for fuses, wiring lines, and protective layers, ensuring reliable operation and extended durability of the liquid discharge head.
Implementation Method 1
heating resistance elements to heat a liquid in a liquid chamber and cause film boiling of the liquid
Implementation Method 2
the plurality of conductive layers include a first conductive layer and a second conductive layer that is less oxidizable than the first conductive layer
Implementation Method 3
a first conductive layer and a second conductive layer that is less oxidizable than the first conductive layer
Data Source
AI summary
A liquid-discharge-head substrate includes a first covering portion covering a first heating resistance element and having electrical conductivity, a second covering portion covering a second heating resistance element and having electrical conductivity, a fuse, and a common wiring line for electrically connecting the first and second covering portions. The common wiring line is electrically connected with the first covering portion via the fuse. The common wiring line and the fuse each have a multilayer structure including a stack of a plurality of conductive layers including a first conductive layer and a second conductive layer that is less oxidizable than the first conductive layer.