Polyamide-imide Adhesive Composition for Flexible PCB Lamination
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Solution Overview
Problem
Existing adhesive compositions for double-sided flexible copper-clad laminates fail to simultaneously achieve high processing ability at low temperature, adhesive property, heat resistance, flame retardancy, and electric insulation, particularly due to limitations in polyamide-imide resin formulations and the presence of nitrile groups and ionic impurities in rubber ingredients.
Innovation Solution
A specific adhesive composition comprising a polyamide-imide resin, an epoxy resin liquid at 25°C, and a phosphorus-type flame retardant, with a glass transition temperature of 250°C or higher, acid value of 50 to 150 mgKOH/g, and a phosphinic acid derivative of phenanthrene type, which forms a strong cross-linking structure for improved heat resistance and insulation while maintaining low-temperature processing ability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If rubber ingredients are added to polyamide-imide resin to improve flexibility and low-warping property, then processing ability at low temperature and adhesive property are improved, but heat resistance and electric insulation deteriorate due to nitrile groups and ionic impurities
Solution Approach 1:
The invention extracts and removes the harmful components (nitrile groups and ionic impurities) from the rubber ingredients by selecting specific hydrogenated nitrile butadiene rubber with controlled unsaturation and low ionic impurity content, thereby eliminating the source of heat resistance and insulation deterioration while preserving the flexibility benefits
Solution Approach 2:
The invention creates a composite adhesive composition combining polyamide-imide resin with hydrogenated nitrile butadiene rubber in a specific ratio (5-50 parts rubber to 100 parts resin), where the composite achieves synergistic effects of both materials while controlling the negative impacts through careful selection of rubber specifications
2Reliability
If thermoplastic polyimide resin is used to achieve adhesive property and heat resistance, then adhesive property and heat resistance are improved, but processing ability at low temperature deteriorates due to high melting temperature requirement of 300°C or higher
Solution Approach 1:
The invention changes the processing temperature parameter from high temperature (300°C or higher required by thermoplastic polyimide) to low temperature (150°C or lower) by selecting thermosetting polyamide-imide resin with appropriate glass transition temperature and curing characteristics, thereby enabling low-temperature processing while maintaining heat resistance through chemical cross-linking
3Reliability
If adhesive composition is designed for high heat resistance and electric insulation, then heat resistance and electric insulation are improved, but processing ability at low temperature and adhesive property may deteriorate
Solution Approach 1:
The invention applies local quality by creating different functional zones within the adhesive composition: the polyamide-imide resin provides heat resistance and insulation in the cured state, while the rubber ingredients provide adhesion and flexibility during processing and in the final product, with each component optimized for its specific function
Solution Approach 2:
The invention introduces dynamic behavior through the curing process, where the adhesive transitions from a soft, processable state at low temperature to a rigid, high-performance state after curing, allowing easy application followed by development of strong adhesive bonds and excellent electrical insulation
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 adhesive composition effectively adheres a copper foil to a polyimide film at 150°C or lower, providing excellent heat resistance, flame retardancy, electric insulation, and dimensional stability, while maintaining flexibility and low-warping properties, making it suitable for flexible printed wiring boards.
Implementation Method 1
which forms a strong cross-linking structure for improved heat resistance and insulation
Implementation Method 2
The adhesive composition effectively adheres a copper foil to a polyimide film at 150°C or lower
Data Source
AI summary
The present invention provide an adhesive composition which is suitable for laminating a polyimide film with a copper foil in a double-sided flexible copper-clad laminate to be used for a flexible printed wiring board. The adhesive composition comprises a polyamide-imide resin, an epoxy resin, and a phosphorus-type flame retardant, wherein 15 to 40 parts by mass of the epoxy resin is compounded to 85 to 60 parts by mass of the polyamide-imide resin; a glass transition temperature of the polyamide-imide resin is 250° C. or higher; an acid value of the polyamide-imide resin is 50 to 150 mgKOH/g; the epoxy resin is liquid at 25° C.; 15 to 60 parts by mass of the phosphorus-type flame retardant is compounded to 100 parts by mass in total of the polyamide-imide resin and the epoxy resin; and 50% by mass or more of the phosphorus-type flame retardant is a phosphinic acid derivative of a phenanthrene type.