Thermoplastic Polyimide Film Alkali Resistance
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Solution Overview
Problem
Polyimide laminated films used in two-layer flexible printed wiring boards (FPCs) face issues with cracking when exposed to alkaline environments during the roll-to-roll manufacturing process, which is not a problem in batch-type processes, and there is a need for improved alkali resistance and peel strength.
Innovation Solution
A polyimide laminated film with a thermoplastic polyimide layer composed of blocks with specific storage elastic moduli, including 4,4′-bis (4-aminophenoxy) biphenyl and 3,3′,4,4′-biphenyltetracarboxylic dianhydride, and diamines like 2,2′-bis [4-(4-aminophenoxy) phenyl] propane and pyromellitic dianhydride, which provides enhanced alkali resistance and adhesion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a polyimide laminated film is used in a roll-to-roll type continuous process, then productivity is improved, but the film develops cracks in alkaline environments
Solution Approach 1:
The invention changes the chemical composition parameters of the polyimide adhesive layer by incorporating specific diamine components (particularly those with rigid aromatic structures like BAPP and ODA) and controlling the imide ring formation degree to 80-95%. This parameter optimization enables the adhesive layer to maintain both processability in continuous manufacturing and resistance to alkaline environments, resolving the contradiction between productivity improvement and reliability maintenance.
Solution Approach 2:
The invention creates a composite structure by combining polyimide adhesive with specific diamine additives that have different chemical properties. The composite adhesive layer contains a base polyimide component for thermal stability and specific diamine components (like BAPP-PMDA or ODA-BPDA) that provide alkali resistance. This composite material approach allows the film to withstand both continuous processing and alkaline exposure without cracking.
2Temperature
If thermosetting adhesives are used in three-layer FPC, then bonding temperature is reduced, but heat resistance deteriorates
Solution Approach 1:
The invention changes the chemical structure parameters of the adhesive by using polyimide-based thermoplastic adhesive with controlled glass transition temperature (Tg) and imide ring formation degree. By adjusting the diamine components and imidization level, the adhesive achieves optimal bonding at moderate temperatures while maintaining high heat resistance, eliminating the need to choose between low bonding temperature and high heat resistance.
Data Source
AI summary
A polyimide laminated film containing a thermoplastic polyimide layer that includes a block (A) having a storage elastic modulus of 0.15 GPa or more at 380° C. and a block (B) having a storage elastic modulus of 0.10 GPa or less at 380° C. is used as a polyimide laminated film that has high peel strength and can suppress occurrence of a crack in an alkaline environment.