Liquid Ejecting Head Flow Path Bonding Before Substrate Thinning
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Solution Overview
Problem
Existing methods face challenges in bonding thin liquid flow paths to other substrates with high accuracy, particularly in liquid ejecting heads and flow path components, where the thinness is required to enhance flow path resistance and flow rate, but precise bonding is difficult due to the complexity of the flow path structures.
Innovation Solution
A manufacturing method that involves direct bonding of first and second flow path substrates without adhesives, followed by thinning the second substrate to achieve high accuracy in bonding and prevent warpage, using techniques like room temperature bonding, fusion bonding, or plasma activation, and employing substrates such as SOI, glass, and silicon with silicon oxide layers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If adhesive bonding is used to bond the first flow path substrate and the second flow path substrate, then the bonding process is simple and easy to implement, but the bonding accuracy and precision are insufficient, especially when the second flow path substrate needs to be made thin
Solution Approach 1:
The patent applies preliminary action by performing direct bonding between the first flow path substrate and the second flow path substrate before thinning the second substrate. This ensures that the bonding interface is established with high precision while the substrate is still at its original thickness, providing mechanical stability during the subsequent thinning process. The bonding is achieved through direct contact and diffusion bonding mechanisms without adhesives, ensuring accurate alignment and positioning.
Solution Approach 2:
The patent replaces the adhesive bonding mechanism with a direct diffusion bonding mechanism. Instead of using adhesive materials that require curing time and precise application, the method uses direct contact bonding where the substrates are bonded through atomic diffusion and metallurgical bonding at the interface. This substitution eliminates adhesive-related positioning errors and provides superior bonding accuracy.
2Productivity
If the second flow path substrate is made thin to increase flow path resistance and flow rate of circulating liquid, then the flow characteristics are improved, but the bonding accuracy deteriorates due to substrate flexibility and warpage
Solution Approach 1:
The patent performs the bonding operation before the thinning operation. The second flow path substrate is bonded to the first substrate while it is still at its original, thicker state, which provides sufficient mechanical rigidity to maintain dimensional stability and prevent warpage during bonding. Only after the bonding is completed does the patent thin the second substrate to achieve the desired flow characteristics.
Solution Approach 2:
The patent provides structural support through the bonding to the first flow path substrate before thinning the second substrate. This pre-established bonding interface acts as a cushioning support that prevents warpage and maintains flatness during the subsequent thinning process, ensuring that the substrate can be thinned to the required thickness without compromising bonding accuracy.
3Reliability
If adhesive bonding is used, then the substrates can be bonded together, but the circulation flow path cannot be effectively formed to remove air bubbles and suppress liquid stagnation
Solution Approach 1:
The patent replaces adhesive bonding with direct diffusion bonding, which creates a seamless, adhesive-free interface between substrates. This enables the formation of continuous circulation flow paths that can effectively remove air bubbles and prevent liquid stagnation. The direct bonding mechanism allows for precise alignment and formation of narrow flow path channels that would be difficult to achieve with adhesive bonding.
Solution Approach 2:
The patent establishes the bonding interface before forming the circulation flow path structures. This preliminary bonding provides a stable foundation for subsequently creating the circulation flow path that connects pressure chambers, enabling effective air bubble removal and liquid circulation without the interference of adhesive layers.
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
This method enables the precise and durable bonding of thin liquid flow paths with improved droplet ejection characteristics and resistance, maintaining the integrity of the flow path structure while reducing the risk of chips or cracks during processing.
Implementation Method 1
a direct bonding step of directly bonding the first flow path substrate and the second flow path substrate without using an adhesive
Implementation Method 2
a thinning step of making the second flow path substrate thinner than the first flow path substrate after the direct bonding step
Data Source
AI summary
A manufacturing method of a liquid ejecting head which has a nozzle and a liquid flow path having a pressure chamber to which a pressure for ejecting droplets from the nozzle is applied, and where a first flow path substrate and a second flow path substrate are bonded to each other, the method including: a direct bonding step of directly bonding the first flow path substrate and the second flow path substrate without using an adhesive; and a thinning step of making the second flow path substrate thinner than the first flow path substrate after the direct bonding step.