Liquid Ejection Head Circuit Board Ink Penetration Resistance
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Solution Overview
Problem
The reliability of inkjet heads decreases due to ink penetration and dissolution of interlayer insulating films, particularly when SiO films dissolve, leading to electrical wiring layer damage and reduced functionality.
Innovation Solution
A liquid ejection head circuit board design featuring a laminated insulating film structure with a first SiOCN film and a second SiOCN film or a low-density insulating film, where the second SiOCN film has a higher carbon content or lower density, respectively, to prevent ink penetration and enhance durability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If SiO is used as the interlayer insulating film, then the manufacturing process is simple and cost-effective, but the film dissolves when ink penetrates, leading to wiring layer damage and reduced reliability
Solution Approach 1:
The insulating film is segmented into multiple layers: a first SiOCN film layer and a second insulating film layer (either SiO or low-density insulating film). This segmentation allows the first layer to provide ink resistance while the second layer maintains manufacturing simplicity and electrical insulation, resolving the contradiction between ease of manufacture and reliability.
Solution Approach 2:
The patent uses composite insulating film structures combining different materials (SiOCN and SiO, or SiOCN and low-density insulating film). The SiOCN layer provides chemical resistance to ink, while the SiO or low-density layer provides good electrical insulation and manufacturing compatibility, achieving both reliability and ease of manufacture through material composition.
2Object-affected harmful factors
If a single-layer SiOCN film is used, then ink penetration resistance is improved, but stress concentration occurs leading to crack propagation and reduced durability
Solution Approach 1:
The insulating film is divided into two layers with different properties. The first SiOCN film layer provides ink penetration resistance, while the second insulating film layer (SiO or low-density film) acts as a stress-absorbing layer that prevents crack propagation, thus improving overall strength while maintaining ink resistance.
Solution Approach 2:
The second insulating film layer serves as a cushioning layer that absorbs stress and prevents cracks from propagating to the first SiOCN film layer. This beforehand cushioning protects the ink-resistant layer from stress-induced damage, maintaining both ink penetration resistance and structural strength.
3Reliability
If the interlayer insulating film dissolves due to ink penetration, then electrical insulation is lost, but using more resistant materials increases manufacturing complexity
Solution Approach 1:
The insulating film is segmented into functional layers: the first SiOCN film layer provides chemical resistance to ink penetration, while the second layer (SiO or low-density insulating film) provides electrical insulation. This segmentation maintains electrical insulation reliability without significantly increasing manufacturing complexity, as both layers can be deposited using standard semiconductor fabrication processes.
Solution Approach 2:
The composite insulating film structure uses materials that can be deposited using existing manufacturing techniques. The SiOCN layer can be formed by CVD or sputtering, and the SiO or low-density layer can be formed by standard dielectric deposition processes, maintaining manufacturing simplicity while achieving superior electrical insulation and ink resistance.
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 laminated film structure effectively prevents ink from reaching the electrical wiring layer, reducing the likelihood of damage and extending the lifespan of the inkjet head by concentrating stress in the second SiOCN film and preventing crack propagation to the first SiOCN film.
Implementation Method 1
the first insulating film is a first SiOCN film, and the second insulating film is a second SiOCN film containing more carbon than the first SiOCN film or a low-density insulating film with a lower density than the first SiOCN film
Implementation Method 2
concentrating stress in the second SiOCN film and preventing crack propagation to the first SiOCN film
Data Source
AI summary
A liquid ejection head circuit board including a substrate, a heat generating resistance element that generates heat energy used for ejection of liquid, an electric wiring layer that is electrically connected to the heat generating resistance element, and an insulating film that insulates the electric wiring layer. The insulating film includes a first insulating film and a second insulating film on the first insulating film, the first insulating film is a first SiOCN film, and the second insulating film is a second SiOCN film containing more carbon than the first SiOCN film or a low-density insulating film with a lower density than the first SiOCN film.