Photosensitive Polyimide Film Alkaline Development
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Solution Overview
Problem
Existing negative photosensitive polyimides are inadequate for development with aqueous alkaline solutions, leading to poor pattern formation and heat resistance issues, particularly in semiconductor and circuit board applications.
Innovation Solution
A photosensitive resin composition comprising a polyimide with alkaline soluble groups, an unsaturated bond-containing polymerizable compound, and a photopolymerization initiator, which becomes insoluble in alkaline solutions after exposure, allowing for pattern formation without high-temperature treatments and reducing curing shrinkage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a photoreactive group is introduced into a polyimide precursor to enable negative photosensitivity, then the material becomes insoluble after exposure, but solubility in aqueous alkaline solution deteriorates and pattern formation becomes difficult
Solution Approach 1:
The invention separates the functions of solubility control and photosensitivity into different components: the polyimide backbone provides structural stability and heat resistance, while side-chain carboxyl groups provide aqueous alkaline solubility. The photoreactive group (acryloyl or methacryloyl) is introduced separately to enable negative photosensitivity without compromising the solubility provided by the carboxyl groups.
Solution Approach 2:
The invention creates a composite structure by combining polyimide with carboxyl-containing side chains and photoreactive groups. This composite material integrates the heat resistance and mechanical strength of polyimide with the solubility of carboxyl groups and the photosensitivity of acryloyl/methacryloyl groups, achieving multiple functions simultaneously.
2Ease of operation
If a polyimide precursor is used to achieve alkaline solubility, then development with aqueous alkaline solution is enabled, but large curing shrinkage occurs during ring closure reaction causing cracking in thick films
Solution Approach 1:
The invention performs preliminary imidization to form the polyimide structure before exposure and development. This eliminates the need for subsequent high-temperature ring closure reactions that cause shrinkage and cracking. The photopolymerization crosslinking occurs after film formation, preventing mechanical stress during the critical development stage.
Solution Approach 2:
The invention replaces the thermal ring closure reaction (which causes mechanical shrinkage and stress) with photopolymerization crosslinking. The photopolymerization occurs at lower temperatures and after the film is already formed and developed, avoiding the mechanical stress and cracking associated with thermal curing of thick films.
3Reliability
If photo acid generator and acid crosslinking agent are added to polyimide to achieve photosensitivity, then pattern formation is enabled, but minute patterns with good reproductivity cannot be formed
Solution Approach 1:
The invention changes the photosensitivity mechanism from acid-catalyzed crosslinking (which has diffusion limitations and poor resolution) to direct photopolymerization of acryloyl/methacryloyl groups. This parameter change enables minute pattern formation with excellent reproductivity while maintaining photosensitivity. The photopolymerization reaction is more localized and controllable than acid diffusion.
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
Enables development with aqueous alkaline solutions, forming polyimide films with excellent heat resistance, strength, and elongation, while preventing cracking and maintaining pattern integrity, even in thick films.
Implementation Method 1
a photopolymerization initiator (c)
Data Source
AI summary
Using a photosensitive resin composition comprising a polyimide (a) having, at the end of the main chain, at least one group selected from the group consisting of a carboxyl group, a phenolic hydroxyl group, a sulfonic acid group and a thiol group, an unsaturated bond-containing polymerizable compound (b1) represented by the general formula (1), and a photopolymerization initiator (c), it is possible to conduct alkaline development and to form a polyimide film having excellent heat resistance, strength and elongation.