Liquid Ejection Head Resin Support Stress Relaxation
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Solution Overview
Problem
Conventional liquid ejection heads using alumina support members face challenges with high-viscosity inks and residual stress issues due to differences in linear expansion coefficients between the silicon substrate and support member, leading to potential cracking or peeling of the ejection port forming member.
Innovation Solution
A liquid ejection head design featuring a resin support member with a pressing unit that applies convex stress to the printing element substrate, using a thermosetting epoxy resin adhesive and ultrasonic welding for the channel unit, and an elastic member to relax residual stress and prevent ink leakage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If alumina is used for the support member to match the linear expansion coefficient of the Si substrate, then stress relaxation during temperature changes is achieved, but heat-retaining performance deteriorates and ink selection is limited
Solution Approach 1:
The patent changes the material parameter of the support member from alumina to resin, accepting a mismatch in linear expansion coefficient with the Si substrate. This parameter change prioritizes heat-retaining performance over perfect stress matching, as the resin material provides better thermal insulation for the ink while the pressing unit compensates for stress issues.
2Temperature
If the Si substrate is mounted on a resin support member, then heat-retaining performance improves, but residual stress from the ejection port forming member causes cracking or peeling
Solution Approach 1:
The pressing unit applies a pre-compressive force to the Si substrate in advance, creating a counter-stress that opposes the tensile stress generated by thermal expansion differences and residual stress from the ejection port forming member. This preliminary anti-action prevents cracking and peeling before they can occur during normal operation.
Solution Approach 2:
The resin support member is pre-formed with a pressing unit structure that will automatically apply compensating stress when the assembly is heated. The pressing unit is positioned and configured in advance to exert force on the Si substrate, creating a pre-stressed state that counteracts future thermal and residual stresses.
3Stability of the object's composition
If high-temperature cure is applied to the epoxy material for the ejection port forming member, then curing is achieved, but residual contraction stress remains on the Si substrate
Solution Approach 1:
The patent accepts the residual contraction stress from high-temperature curing as an inevitable byproduct, but converts this potentially harmful stress into a beneficial pre-compressive state by using the pressing unit to apply an opposing force. The harmful residual stress is thus transformed into a controlled pre-stress condition that, when counterbalanced, improves overall structural stability.
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 effectively suppresses cracking and peeling of the silicon substrate and ejection port forming member, enhancing environmental reliability and allowing for the use of high-viscosity inks while maintaining manufacturing efficiency.
Implementation Method 1
the support member includes a pressing unit configured to press so that a center part on a surface opposite to a surface on which the printing element substrate of the printing element unit is mounted becomes convex
Implementation Method 2
a material of the adhesive uses a thermosetting epoxy resin
Implementation Method 3
ultrasonic welding for the channel unit
Implementation Method 4
an elastic member to relax residual stress and prevent ink leakage
Data Source
AI summary
A liquid ejection head with high environmental reliability which suppresses a crack of a Si substrate and peeling-off of an ejection port forming member by relaxing a residual stress in a printing element substrate and a manufacturing method of a liquid ejection head are provided. For that purpose, after the printing element substrate is bonded and fixed to a support member, the support member is screwed and fixed through an elastic member.