Liquid Ejection Head Substrate Hole Design for Connection Reliability
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Solution Overview
Problem
The existing liquid ejection heads face challenges in maintaining the reliability and strength of element substrates due to the formation of hole portions for electric connection portions, which can lead to deformation and affect the reliability of the electric connections.
Innovation Solution
A liquid ejection head design where a hole portion is formed in the substrate from a second surface opposite to the energy generating element surface, with a larger area at the second surface compared to the bottom portion, allowing for the placement of electric connection members without compromising the substrate's strength, and a manufacturing method involving etching and wire lead bonding to connect terminals and electric connection members.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If hole portions are formed in the substrate for electric connection portions, then electric connections can be established, but the substrate strength and reliability are reduced due to deformation
Solution Approach 1:
The patent applies local quality by creating a tapered hole structure where the cross-sectional area varies along the depth. The hole has a larger cross-sectional area at the entrance (first end) and a smaller cross-sectional area at the bottom (second end), allowing the electric connection portion to be firmly secured at the bottom while the tapered walls provide structural reinforcement. This local geometric variation optimizes both connection reliability and substrate strength without requiring the entire substrate to be thicker.
2Strength
If the substrate is made thicker to prevent deformation, then substrate strength is improved, but the overall device size and complexity increase
Solution Approach 1:
The patent resolves the contradiction by transitioning from a uniform two-dimensional hole cross-section to a three-dimensional tapered structure. The hole portion extends in the depth direction with varying cross-sectional area, creating a conical or frustoconical geometry. This dimensional change allows the hole to provide both connection access and structural reinforcement functions simultaneously, eliminating the need for additional thickening of the entire substrate.
3Device complexity
If electric connection portions are formed on the same surface as ejection ports, then device structure is simplified, but cleaning operation is affected due to blade member interference
Solution Approach 1:
The patent applies inversion by placing the electric connection portions on the back surface of the substrate rather than on the front surface where ejection ports are located. The tapered holes penetrate through the substrate thickness, allowing electrical connections to be made from the rear side. This spatial inversion separates the cleaning blade's path on the front surface from the electric connection areas on the back surface, eliminating interference while maintaining a compact overall structure.
Data Source
AI summary
A liquid ejection head includes an ejection port member that includes an ejection port that ejects a liquid, an energy generating element that generates energy for ejecting the liquid from the ejection port, a terminal electrically connected to the energy generating element, and a substrate portion that supports the ejection port member, the energy generating element, and the terminal. The terminal is connected to a wire member that supplies electric power that drives the energy generating element to the energy generating element, the substrate portion includes a hole portion formed from a surface of the substrate portion on a side opposite to a surface of the substrate portion on which the terminal is provided to a surface where the terminal is exposed, and an area of the surface where the terminal is exposed is smaller than an area of an opening of the hole portion.