Liquid Ejection Head Wiring Substrate Groove Bonding
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Solution Overview
Problem
The reliability of electric wiring substrates in liquid ejection heads is compromised due to differences in linear expansion coefficients between the wiring substrates and support members, leading to potential wiring breakage from temperature changes.
Innovation Solution
A method is developed where the electric wiring substrate is bonded to support members with a specific alignment and pressure technique, allowing it to straddle a groove and be bonded between two support surfaces using adhesives, which reduces tension and stress caused by thermal expansion differences.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the electric wiring substrate is directly bonded to the support member, then the bonding process is simple, but the wiring substrate is prone to breakage due to thermal expansion differences
Solution Approach 1:
The support member is divided into two separate support surfaces (first support surface and second support surface) that are positioned at different locations. The wiring substrate is bonded to both support surfaces, creating a segmented bonding structure that allows the substrate to straddle the groove between them. This segmentation reduces thermal stress concentration and prevents wiring breakage during thermal expansion.
Solution Approach 2:
A groove is introduced as an intermediary structural feature between the first and second support surfaces. The wiring substrate spans across this groove, and the groove acts as a stress-relief zone that accommodates thermal expansion differences. This intermediary structure mediates the thermal stress between the wiring substrate and the support member, preventing direct stress transmission that would cause wiring breakage.
2Manufacturing precision
If the wiring substrate is tensioned during bonding to ensure alignment, then alignment accuracy is improved, but the wiring becomes more susceptible to breakage from thermal stress
Solution Approach 1:
The wiring substrate is bonded to the first support surface and second support surface in a predetermined sequence, with the groove position pre-planned. This preliminary arrangement of the bonding structure ensures that the substrate is not under continuous tension, as the groove provides a natural stress-relief zone. The predetermined bonding positions maintain alignment accuracy while preventing excessive tension that would make the wiring susceptible to thermal stress breakage.
3Reliability
If the wiring substrate is made more flexible to accommodate thermal expansion, then thermal stress is reduced, but the structural integrity and connection strength may be compromised
Solution Approach 1:
The wiring substrate has different structural characteristics at different locations: it is bonded rigidly to the first support surface and second support surface to ensure strong connections, while spanning flexibly across the groove to accommodate thermal expansion. This local quality differentiation allows the substrate to exhibit both strength where needed (at bonding points) and flexibility where needed (over the groove), resolving the contradiction between connection strength and thermal stress resistance.
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 enhances the reliability of the electric wiring substrate by minimizing the risk of wiring damage from temperature-induced stress, ensuring consistent alignment and connection accuracy.
Implementation Method 1
overlapping a second portion of the electric wiring substrate and a second support surface through an adhesive so that the electric wiring substrate straddles a groove
Implementation Method 2
pressing the second portion and a third portion by a pressing tool to bond the second portion and the second support surface
Data Source
AI summary
Reliability of an electric wiring substrate against a change in temperature in a liquid ejection head can be achieved. The liquid ejection head has an element substrate and an electric wiring substrate. Upon manufacturing the liquid ejection head, a second portion of the electric wiring substrate overlaps a second support surface through an adhesive so that the electric wiring substrate straddles a groove between a first support surface to which a first portion, which is one end of an electric wiring substrate, is bonded and a second support surface, and a second portion and a third portion are pressed by a pressing tool so that the third portion of the electric wiring substrate, which is a portion between the first portion and the second portion, is pushed into the groove, and the second portion is bonded to the second support surface.