Flat Flexible Substrate Insulation for Recording Head Wiring Protection
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Solution Overview
Problem
In ink-jet recording heads, the separation of a flat flexible substrate from the actuator unit during manufacturing can occur, leading to potential damage to the wiring pattern due to repeated contacts with the actuator unit corners, which compromises the integrity of the recording head.
Innovation Solution
A manufacturing method involving a flat flexible substrate with an insulating land cover layer and an insulating wiring cover layer, where the land cover layer is thermally cured to fix the substrate to the actuator unit, preventing separation and damage by sandwiching the wiring cover layer between the land cover layer and the piezoelectric layer, thus securing the bonded points and reducing stress on the substrate.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a cover film is used to fix the flat cable to the actuator unit surface, then the separation of the flat cable from the actuator unit is prevented, but the flat cable may sag and contact the actuator unit corner, causing damage to the wiring pattern
Solution Approach 1:
The patent introduces a buffer layer (insulating layer) between the flat flexible substrate and the actuator unit corner. This intermediary layer prevents direct contact between the substrate and the sharp corner, eliminating the harmful effect while maintaining the fixing function. The buffer layer absorbs the mechanical stress and prevents the substrate from sagging onto the corner during assembly and operation.
Solution Approach 2:
The patent applies a protective insulating layer to the actuator unit surface before assembling the flat flexible substrate. This pre-applied protective layer cushions against potential contact damage, preventing the wiring pattern from being damaged by the sharp corner of the actuator unit before assembly is complete.
2Ease of manufacture
If the flat cable is pulled upward during manufacturing, then the cable can be connected to the driver IC, but a force is exerted that may separate the lands from the bumps
Solution Approach 1:
The patent forms the insulating layer with protrusions that extend beyond the edge of the actuator unit before assembly. This preliminary preparation ensures that when the flat flexible substrate is assembled, the protrusions of the insulating layer make contact first, guiding the alignment and preventing excessive force from being applied to the bump-land bonding points during the pulling and connection process.
Solution Approach 2:
The insulating layer acts as an intermediary element that manages the mechanical stress during assembly. The protrusions of the insulating layer provide a controlled contact point that mediates the force application, allowing the flat cable to be pulled and connected to the driver IC without exerting excessive force on the bump-land bonding points.
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 effectively suppresses the separation of the flat flexible substrate from the actuator unit and reduces the risk of damage to the wiring pattern, enhancing the reliability and longevity of the recording head.
Implementation Method 1
an actuator unit which is fixed to the passage unit and causes the passage unit to eject liquid; The actuator unit has a piezoelectric layer having a surface A facing the substrate
Implementation Method 2
a step of fixing the land cover layer to the piezoelectric layer by thermally curing the land cover layer as the substrate is contacted to the actuator unit
Data Source
AI summary
A flat flexible substrate of a recording head has: a base having a surface facing an actuator unit, a plurality of lands placed on the surface and bonded to respective individual bumps, a plurality of wirings placed on the surface and connected to the respective lands, an insulating land cover layer covering parts of the respective lands other than the bonded points with the respective individual bumps, and an insulating wiring cover layer covering the wirings. The wiring cover layer and the land cover layer are placed on each other to form a layered part so that the wiring cover layer is sandwiched between the land cover layer and the wirings, and a piezoelectric layer and the wirings sandwich therebetween at least a part of the layered part. In the layered part, the land cover layer is fixed to the piezoelectric layer.