Liquid Ejection Head Adhesive Modulus for Thermal Stress
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Solution Overview
Problem
In page-wide liquid ejection recording systems, thermal expansion of support members causes tensile stress on electrical wiring boards, leading to potential defects and reduced accuracy of print chip arrangement due to the need for heating processes, which existing techniques struggle to mitigate effectively.
Innovation Solution
A liquid ejection head design where the electrical wiring board is bonded to both a first support member with a higher elastic modulus adhesive and a second support member with a greater linear expansion coefficient, using adhesives with varying elastic moduli to absorb and distribute thermal stress, ensuring reliable electrical connections and maintaining print chip accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the support member is heated to cure the seal, then the seal is properly cured, but the support member thermally expands and applies tensile stress to the electrical wiring board
Solution Approach 1:
The patent applies beforehand cushioning by bonding the electrical wiring board to the support member in a preheated state before the seal curing process. This creates slack in the electrical connection portion that absorbs the thermal expansion stress when the support member is heated for seal curing, preventing tensile stress from damaging the wiring board
Solution Approach 2:
The patent changes the temperature parameter during the bonding process by bonding the electrical wiring board in a heated state rather than at room temperature. This parameter change allows the support member to be in an expanded state during bonding, so that subsequent cooling creates slack that cushions against thermal expansion stress during operation
2Reliability
If the electrical wiring board is bonded with a fixing tool to create slack, then reliability against temperature changes is improved, but the arrangement accuracy of print chips is reduced
Solution Approach 1:
The patent applies preliminary action by performing the bonding of the electrical wiring board to the support member before the seal curing process and before final assembly. This preliminary bonding in a heated state establishes the slack needed for thermal expansion compensation without interfering with subsequent print chip arrangement operations
3Adaptability or versatility
If the support member has a greater linear expansion coefficient to accommodate thermal changes, then adaptability to temperature changes is improved, but the accuracy of print chip arrangement is degraded due to heating influence
Solution Approach 1:
The patent changes the temperature parameter during bonding to compensate for the greater linear expansion coefficient of the support member. By bonding in a heated state, the support member is already expanded, so subsequent cooling creates slack that accommodates thermal expansion during operation without requiring excessive heating that would degrade print chip arrangement accuracy
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 design reduces tensile stress on electrical wiring boards during thermal expansion, enhancing the reliability of the electrical connections and maintaining the accuracy of print chip arrangement, thereby improving the overall reliability and performance of the liquid ejection head.
Implementation Method 1
a second support member supporting the first support member and having a greater linear expansion coefficient than the electrical wiring board
Implementation Method 2
an adhesive that bonds the electrical wiring board to the second surface has a lower elastic modulus than an adhesive that bonds the electrical wiring board to the first surface
Data Source
AI summary
A liquid ejection head includes a recording element substrate including an energy generating element configured to generate energy for ejecting liquid from an ejection port; an electrical wiring board electrically connected to the recording element substrate to supply an electric signal for driving the energy generating element; a first support member supporting the recording element substrate; and a second support member supporting the first support member and having a greater linear expansion coefficient than that of the electrical wiring board. The electrical wiring board is bonded to a first surface of the first support member and a second surface of the second support member, and an adhesive that bonds the electrical wiring board to the second surface has a lower elastic modulus than that of an adhesive that bonds the electrical wiring board to the first surface.