Negative Photosensitive Material for HDD Suspension Boards
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Solution Overview
Problem
Current polyimide precursor materials used in HDD suspension boards suffer from inferior gradational patternability and PI etchability, leading to warpage issues due to high rigidity and hygroscopic expansion, which complicates the formation of precise patterns and reliable connections.
Innovation Solution
A negative photosensitive material comprising a polyimide precursor with specific structural units and pyridine derivatives, used in conjunction with a photosensitive board and a pattern forming method involving exposure and heat treatment, to achieve low linear and hygroscopic expansion coefficients, enabling excellent gradational patternability and PI etchability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If polyimide precursor material is used to reduce hygroscopic expansion coefficient and linear expansion coefficient, then warpage is reduced, but gradational patternability and PI etchability deteriorate
Solution Approach 1:
The patent modifies the chemical structure of the polyimide precursor by introducing specific structural units (formulae 1 and 2) with controlled proportions (structural unit 2 at less than 30 mol%). This parameter change in molecular structure achieves low hygroscopic expansion coefficient while simultaneously improving gradational patternability and PI etchability, resolving the contradiction between material stability and manufacturing precision.
2Stability of the object's composition
If polyimide precursor material is used to reduce hygroscopic expansion coefficient and linear expansion coefficient, then warpage is reduced, but PI etchability deteriorates
Solution Approach 1:
The patent changes the chemical composition parameters of the polyimide precursor by incorporating structural units represented by formulae (1) and (2) in specific ratios. This molecular-level parameter adjustment enables the material to maintain low linear expansion coefficient for warpage reduction while simultaneously achieving excellent PI etchability for ease of manufacture.
3Strength
If metal substrate proportion is reduced to lower rigidity, then suspension board rigidity is reduced, but warpage increases
Solution Approach 1:
The patent creates a composite material system combining polyimide precursor with specific structural units (formulae 1 and 2) and photoinitiators. This composite photosensitive composition achieves unique properties where the cured product provides both low rigidity (for suspension board flexibility) and low warpage (through controlled expansion coefficients), resolving the contradiction between strength and shape stability.
4Ease of manufacture
If epoxy resin photosensitive material is used, then ease of manufacture is good, but hygroscopic expansion coefficient and linear expansion coefficient are high
Solution Approach 1:
The patent fundamentally changes the material composition from epoxy resin to a specifically designed polyimide precursor system with structural units (formulae 1 and 2). This parameter change in base material chemistry simultaneously achieves ease of manufacture through photosensitive curing while dramatically reducing both hygroscopic and linear expansion coefficients for improved dimensional 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 solution allows for the formation of flat terminals with reliable connections, reducing warpage and improving the mechanical strength and solution storage stability of the suspension boards, while maintaining low expansion coefficients.
Implementation Method 1
irradiating a surface of a film of the negative photosensitive material or a surface of the coating film of the photosensitive board with activation radiation
Implementation Method 2
heat-treating the film at a temperature not lower than 170° C.
Data Source
AI summary
A negative photosensitive material is provided which has a lower linear expansion coefficient and a lower hygroscopic expansion coefficient and is excellent in gradational patternability and PI etchability in patterning. The negative photosensitive material comprises:(A) a polyimide precursor having a structural unit represented by the following general formula (1) and a structural unit represented by the following general formula (2), the structural unit represented by the general formula (2) being present in the polyimide precursor in a proportion of less than 30 mol % based on the overall amount of the polyimide precursor; and(B) at least one of a pyridine derivative represented by the following general formula (3) and a pyridine derivative represented by the following general formula (4):wherein R1, R2, R3, R4 and R5, which may be the same or different, are each a C1 to C4 alkyl group, and Ar is an aryl group having a nitro group at its ortho position,wherein R1, R2, R4 and R5, which may be the same or different, are each a C1 to C4 alkyl group, and Ar is an aryl group having a nitro group at its ortho position.