Epoxy Laminate with Di-isoimide for Flexible PCBs
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Solution Overview
Problem
Epoxy compositions used in flexible printed wiring boards are flammable and require flame retardants, and they have a limited shelf life due to rapid curing, which complicates their use in electronics where high temperatures and stability are necessary.
Innovation Solution
A curable epoxy composition incorporating a di-isoimide composition that acts as both a cross-linking agent and catalyst, reducing the need for flame retardants and extending shelf life by using a specific process involving pyromellitic dianhydride and di-amino triazine, which forms a stable di-isoimide that reacts with epoxy to create a non-flammable, fully cured product.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional epoxy composition is used, then the material provides good adhesive strength and flexibility, but it is flammable and has a limited shelf life
Solution Approach 1:
The patent changes the chemical parameters of the epoxy system by introducing a di-isoimide compound with specific molecular structure (Structure I) that modifies the curing characteristics. This parameter change transforms the epoxy from a rapidly curing, flammable system to one with extended shelf life and reduced flammability through the unique chemical properties of the di-isoimide
Solution Approach 2:
The invention creates a composite curing system combining epoxy resin with di-isoimide compound and optional flame retardant additives. This composite material approach allows the epoxy to benefit from both the adhesive strength of conventional epoxies and the stability properties of the di-isoimide, while optionally incorporating flame retardants to further address flammability concerns
2Object-affected harmful factors
If a flame retardant is added to the epoxy composition, then fire resistance is improved, but the composition becomes more complex and may affect shelf life
Solution Approach 1:
The di-isoimide compound serves multiple functions simultaneously: it acts as a curing agent, extends shelf life, and provides inherent flame retardancy. This multi-functionality reduces the need for separate flame retardant additives, thereby simplifying the overall composition while achieving fire resistance
Solution Approach 2:
The epoxy-dii-isoimide system provides its own flame retardant properties through the chemical structure and curing characteristics of the di-isoimide compound, eliminating the need for external flame retardant additives in many cases. The system essentially serves its own fire resistance needs through its intrinsic properties
3Reliability
If a latent curing catalyst activated at high temperature is used, then shelf life is extended, but the curing temperature may degrade electronic circuit elements
Solution Approach 1:
The patent optimizes the chemical parameters of the curing system by selecting a di-isoimide compound with appropriate reactivity and activation characteristics. This allows the system to achieve long shelf life at room temperature while curing at moderate temperatures (typically 80-150°C) that are safe for electronic components
Solution Approach 2:
The di-isoimide compound acts as an intermediary between the epoxy resin and the curing process, providing a controlled reaction pathway that enables long-term stability at room temperature followed by effective curing at moderate temperatures. It mediates the curing reaction to occur at temperatures suitable for electronic applications
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 di-isoimide composition effectively reduces flammability and extends the shelf life of the epoxy, allowing for stable curing at elevated temperatures without degrading electronic components, thus enhancing the properties of the resulting flexible printed wiring boards.
Implementation Method 1
a curable composition comprising an epoxy and a novel aromatic di-isoimide chemical compound
Implementation Method 2
heating the curable composition to a temperature in the range of 100 to 250° C. for a period of time in the range of 30 seconds to 5 hours, thereby forming the corresponding cured composition
Data Source
AI summary
The present invention deals with a laminate useful for forming fully encapsulated flexible printed wiring boards. The laminate comprises a dielectric substrate coated with a curable composition comprising an epoxy and a novel aromatic di-isoimide chemical compound. The curable composition provides the benefit of thermal latency, improving shelf-life, and reducing premature curing during processing. Fully encapsulated printed wiring boards are also disclosed.