Inkjet Head Substrate Thermal Expansion Matching
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Solution Overview
Problem
The existing inkjet heads experience warping due to differences in thermal expansion coefficients of their substrates, leading to issues with ink ejection angles, leakage, and electrical connections, particularly when exposed to temperature variations during operation and manufacturing.
Innovation Solution
The inkjet head design ensures that the pressure-chamber substrate, diaphragm, spacer substrate, and wiring substrate have thermal expansion coefficients equal to or less than 3.5 × 10^-6 /°C, with materials like silicon and 42 alloy, and a spacer substrate thickness of 50 μm to 200 μm, along with surface treatments, to minimize thermal expansion and maintain substrate integrity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If multiple substrates with different materials are stacked to form the inkjet head structure, then the device complexity is reduced and manufacturing is simplified, but warping occurs due to differences in coefficients of thermal expansion
Solution Approach 1:
The patent changes the material parameters of the substrates by selecting materials with matched coefficients of thermal expansion (all within 3.5×10^-6 /°C). This parameter matching prevents differential thermal expansion and eliminates warping while maintaining the simplified multi-substrate structure
Solution Approach 2:
The patent uses composite material selection where silicon substrates (coefficient: 2.5×10^-6 /°C) are combined with 42 alloy (coefficient: 13×10^-6 /°C) in a controlled manner, and more importantly, ensures all critical substrates (pressure-chamber, diaphragm, spacer, wiring) have matched thermal expansion coefficients to prevent warping
2Productivity
If the inkjet head is heated during operation to eject ink, then the ink ejection function is achieved, but substrate warping occurs due to thermal expansion differences
Solution Approach 1:
The patent changes the thermal parameter matching between substrates by selecting materials with identical or closely matched coefficients of thermal expansion. This ensures that during ink ejection heating, all substrates expand uniformly without relative warping, maintaining structural stability while achieving the ink ejection function
Solution Approach 2:
The patent converts the potentially harmful effect of thermal expansion into a beneficial uniform expansion by matching material properties. The heat required for ink ejection no longer causes warping but instead produces controlled, uniform expansion that maintains the integrity of the multi-substrate structure
3Reliability
If substrates are separated due to warping, then manufacturing defects occur, but preventing separation requires tighter material specifications
Solution Approach 1:
The patent establishes a specific parameter threshold (coefficient of thermal expansion ≤ 3.5×10^-6 /°C) for substrate materials. This quantitative specification ensures reliable electrical connections by preventing warping-induced separation, while still allowing practical material choices like silicon and 42 alloy that meet the criterion
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 design prevents warping and separation of substrates, ensuring consistent ink ejection, reducing ink leakage, and maintaining reliable electrical connections, thereby enhancing the overall performance and accuracy of the inkjet head.
Implementation Method 1
a spacer substrate disposed on an opposite side of a diaphragm from the predetermined direction... in a space formed by the spacer substrate between the wiring substrate and the diaphragm
Implementation Method 2
actuators in contact with the diaphragm... the actuators being electrically connected to respective wires of the wiring substrate
Implementation Method 3
the ink in the ink jet head before being ejected is heated, and the inkjet head is also heated by the heat of the ink
Implementation Method 4
the heat causes warps in the inkjet head due to the differences in coefficients of thermal expansion of the substrates constituting the individual layers
Data Source
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AI summary
This invention prevents problems due to substrate warpage. This inkjet head (1) is provided with the following: a pressure-chamber substrate (20) in which a pressure chamber (21) that contains ink is formed, said pressure chamber (21) being provided so as to connect to a nozzle (N) from which ink is discharged downwards; a spacer substrate (40) laminated to the top of a diaphragm (30) that is laminated to the top of the pressure-chamber substrate (20) and forms one side of the pressure chamber (21) ; a wiring substrate (50) laminated to the top of the spacer substrate (40); and an actuator (60) that is provided so as to contact the diaphragm (30) inside a space formed by the spacer substrate (40) between the wiring substrate (50) and the diaphragm (30) and is electrically connected to wiring (52) on the wiring substrate (50). The differences between the thermal-expansion coefficients of the pressure-chamber substrate (20), the diaphragm (30), the spacer substrate (40), and the wiring substrate (50) are all less than or equal to a prescribed value.